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Stanciucu M Mihaela2018, Encyclopedia of earth sciences
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A series of rock-joint behavior routines which, briefly stated, allow the shear strength and normal stiffness of rock joints to be estimated, graphed, and numerically modelled, for instance, in the computer code UDEC-BB. Coupled behavior with deformation and changes in conductivity is also included (Barton 2016). A key aspect of the criterion is the quantitative characterization of the joint, joints, or joint sets in question, in order to provide three simple items of input data. These concern the joint-surface roughness (JRC: joint roughness coefficient), the joint-wall compressive strength (JCS: joint compressive strength), and an empirically derived estimate of the residual friction angle (' r). These three parameters have typical ranges of values from: JRC = 0 to 20 (smooth-planar to very rough-undulating), JCS = 10 to 200 MPa (weakweathered to strong, unweathered) and j r = 20 to 35 (strongly weathered to fresh-unweathered). Each of these parameters can be obtained from simple, inexpensive index tests or can be estimated by those with experience. The three parameters JRC, JCS, and j r form the basis of the nonlinear peak shear-strength equation of Barton (1973) and Barton and Choubey (1977). This is a curved shear strength envelope without cohesion (c). It will be contrasted to the linear Mohr-Coulomb "c and j" (with apparent cohesion) criterion later. To be strictly correct the original Barton equation utilized the basic friction angle j b of flat, unweathered rock surfaces (in 1973), whereas j r was Barton-Bandis Criterion 55 B Cross-References ▶ Mohr-Coulomb Failure Envelope ▶ Rock Mass Classification ▶ Shear Strength References Bakhtar K, Barton N (1984) Large scale static and dynamic friction experiments. In: Proceedings of 25th US rock mechanics symposium. Northwestern University, Evanston Barton-Bandis Criterion, Fig. 8 The nonlinear modelling of joint closure by Bandis (1980) and Bandis et al. (1983). The three loadunload cycles are designed to mirror the experimental evidence of a large hysteresis on the first cycle due to the unavoidable effects of taking a (drill-core) sample which releases the original in situ normal stress. The first load cycle re-closes the joint. The properly consolidated (cycle 3) behavior is incorporated in the distinct-element (jointed) code UDEC-BB Barton-Bandis Criterion Bandis S (1980) Experimental studies of scale effects on shear strength, and deformation of rock joints. PhD thesis,
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Nonlinear shear behavior of rock joints using a linearized implementation of the BartoneBandis model-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0
Experiments on rock joint behaviors have shown that joint surface roughness is mobilized under shearing, inducing dilation and resulting in nonlinear joint shear strength and shear stress vs. shear displacement behaviors. The BartoneBandis (BeB) joint model provides the most realistic prediction for the nonlinear shear behavior of rock joints. The BeB model accounts for asperity roughness and strength through the joint roughness coefficient (JRC) and joint wall compressive strength (JCS) parameters. Nevertheless, many computer codes for rock engineering analysis still use the constant shear strength parameters from the linear MohreCoulomb (MÀC) model, which is only appropriate for smooth and non-dilatant joints. This limitation prevents fractured rock models from capturing the nonlinearity of joint shear behavior. To bridge the BeB and the MÀC models, this paper aims to provide a linearized implementation of the BeB model using a tangential technique to obtain the equivalent MÀC parameters that can satisfy the nonlinear shear behavior of rock joints. These equivalent parameters, namely the equivalent peak cohesion, friction angle, and dilation angle, are then converted into their mobilized forms to account for the mobilization and degradation of JRC under shearing. The conversion is done by expressing JRC in the equivalent peak parameters as functions of joint shear displacement using proposed hyperbolic and logarithmic functions at the pre-and post-peak regions of shear displacement, respectively. Likewise, the pre-and post-peak joint shear stiffnesses are derived so that a complete shear stress-shear displacement relationship can be established. Verifications of the linearized implementation of the BeB model show that the shear stress-shear displacement curves, the dilation behavior, and the shear strength envelopes of rock joints are consistent with available experimental and numerical results.
The shear strength of rock joints in theory and practice
Rock Mechanics and Rock Engineering, 1977
The Shear Strength of Rock Joints in Theory and Practice The paper describes an empirical law of friction for rock joints which can be used both for extrapolating and predicting shear strength data. The equation is based on three index parameters; the joint roughness coefficientJRC, the joint wall compressive strengthJCS, and the residual friction angleφ r . All these index values can be measured in the laboratory. They can also be measured in the field. Index tests and subsequent shear box tests on more than 100 joint samples have demonstrated thatφ r can be estimated to within ± 1° for any one of the eight rock types investigated. The mean value of the peak shear strength angle (arctanτ/σ n ) for the same 100 joints was estimated to within 1/2°. The exceptionally close prediction of peak strength is made possible by performing self-weight (low stress) sliding tests on blocks with throughgoing joints. The total friction angle (arctanτ/σ n ) at which sliding occurs provides an estimate of the joint roughness coefficientJRC. The latter is constant over a range of effective normal stress of at least four orders of magnitude. However, it is found that bothJRC andJCS reduce with increasing joint length. Increasing the length of joint therefore reduces not only the peak shear strength, but also the peak dilation angle and the peak shear stiffness. These important scale effects can be predicted at a fraction of the cost of performing large scale in situ direct shear tests. Die Scherfestigkeit von Kluftflächen in Theorie und Praxis Zur Ermittlung der Reibungswerte in Kluftflächen wird ein empirisches Gesetz beschrieben, das sowohl das Extrapolieren als auch das Voraussagen von Scherfestigkeitszahlen ermöglicht. Die Gleichung ist auf drei Indexzahlen gegründet: Den Rauhigkeitskoeffizienten der KluftJRC (Joint Roughness Coeff.), die Druckfestigkeit des Felses der KluftwändeJCS (Joint Wall Compression Strength) und der residuelle Reibungswinkel der Trennflächeφ r . Die Indexzahlen können alle im Laboratorium bestimmt oder am Ort gemessen werden. Bestimmung von Indexzahlen mit nachfolgenden Prüfungen im Scherapparat von mehr als 100 Kluftproben haben erwiesen, daß für jede beliebige der acht untersuchten Gesteinsarten der Reibungswinkelφ r auf ± 1° genau geschätzt werden kann. Der Durchschnittswert des Reibungswinkels (arc tan (τ/σ n ) der Höchstscherfestigkeit wurde für dieselben 100 Klüfte auf ± 1/2° genau geschätzt. Die besonders genaue Vorausschätzung der Höchstscherfestigkeit ist durch Eigengewicht-Gleitversuche (niedrige Spannungen) auf Gesteinsblöcken mit durchgehenden Trennflächen ermöglicht. Der totale Reibungswinkel (arc tanτ/σ n ), bei dem das Gleiten eintrifft, ergibt eine Abschätzung des Rauhigkeitskoeffizienten der KluftJRC. Der Rauhigkeitskoeffizient bleibt über einen Normal-Spannungsbereich von mindestens vier Größenanordnungen konstant. Die IndexzahlenJRC (Rauhigkeitskoeffizient) undJCS (Druckfestigkeitskoeffizient) reduzieren sich aber bei zunehmenden Kluftlängen. Bei zunehmender Kluftflächengröße nehmen nicht nur die Höchstscherfestigkeit, sondern auch der zugehörige Dilatanzwinkel und die Schubsteifigkeit ab. Diese wichtigen Einflüsse der geometrischen Abmessungen können geschätzt und zahlenmäßig erfaßt werden, und zwar mit Kosten, die nur einen Bruchteil von denen betragen, die für große, direkte Scherversuche in situ erforderlich wären. La résistance au cisaillement des joints de roches en théorie et en pratique Le rapport traite d'une loi empirique du frottement dans les joints de roches, loi pouvant être utilisée tant pour l'extrapolation que pour la prédiction de données relatives à la résistance au cisaillement. L'équation est basée sur trois indices de paramètres: coefficient de rugosité du joint (joint roughness coefficient —JRC), résistance de la paroi à la compression (joint wall compressive strength —JCS), et l'angle de frottement résiduelφ r . Toutes ces valeurs d'indice peuvent être mesurées au laboratoire. Elles peuvent aussi l'être in situ. Des tests d'indice, avec ensuite des tests en boîte de cisaillement, sur plus de 100 échantillons de joints, ont permis de constater que, pour n'importe quel des huit types de roche étudiés, l'angle de frottementφ r peut être évalué avec une précision de ± 1°. La valeur moyenne de l'angle maximum de la résistance au cisaillement (arctanτ/σ n ) pour les mêmes 100 joints fut évaluée avec une précision de 1/2°. La prédiction particulièrement précise de la résistance maximum au cisaillement est rendue possible par la réalisation d'essais de glissement dits “de poids propre” (faible contrainte) sur des blocs à joints passant de part en part. L'angle de frottement total (arctanτ/σ n ) auquel le glissement se manifeste, fournite une estimation du coefficient de rugosité du joint,JRC. Ce dernier est constant à l'intérieur d'une plage de tensions normales effectives d'au moins quatre ordres de grandeur. Cependant, on a trouvé que les indicesJRC (rugosité) comme ceuxJCS (compression) diminuent quand la longueur du joint augmente. Ainsi, si la langueur du joint augmente, cela réduira non seulement la résistance maximum au cisaillement, mais aussi l'angle maximum de dilatation et la rigidité maximum de cisaillement. Ces importants effets d'échelle peuvent être prédits, et ce à des coûts ne représentant qu'une fraction de ceux liés à des tests directs de cisaillement effectués in situ.
Shear strength criteria for rock, rock joints, rockfill and rock masses: Problems and some solutions
Although many intact rock types can be very strong, a critical confining pressure can eventually be reached in triaxial testing, such that the Mohr shear strength envelope becomes horizontal. This critical state has recently been better defined, and correct curvature or correct deviation from linear Mohr-Coulomb (M-C) has finally been found. Standard shear testing procedures for rock joints, using multiple testing of the same sample, in case of insufficient samples, can be shown to exaggerate apparent cohesion. Even rough joints do not have any cohesion, but instead have very high friction angles at low stress, due to strong dilation. Rock masses, implying problems of large-scale interaction with engineering structures, may have both cohesive and frictional strength components. However, it is not correct to add these, following linear M-C or nonlinear Hoek-Brown (H-B) standard routines. Cohesion is broken at small strain, while friction is mobilized at larger strain and remains to the end of the shear deformation. The criterion 'c then n tan ϕ' should replace 'c plus n tan ϕ' for improved fit to reality. Transformation of principal stresses to a shear plane seems to ignore mobilized dilation, and caused great experimental difficulties until understood. There seems to be plenty of room for continued research, so that errors of judgement of the last 50 years can be corrected.
Shear Behaviour of Rock Joints
2000
This title covers the fundamental properties of rock joints, the method of laboratory testing of rock joints, and shear strength assessment under different loading conditions. This work is intended as a reference text for students and practitioners in mining and rock engineering.
Modelling the shear behaviour of sedimentary rock joints under constant normal stiffness conditions
The typical shear behaviour of rock joints has been studied under a constant normal load (CNL) or zero normal stiffness condition, but recent studies have shown that this boundary condition may not replicate more practical situations, and that constant normal stiffness (CNS) is a more appropriate boundary condition to describe the stress-strain response of field joints. In addition to the effect of boundary conditions, the shear behaviour of a rough joint also depends on its surface properties and the initial stress acting on its interface. Despite this, exactly how these parameters affect the shear behaviour of joints is not fully understood because the stress-strain response of joints is governed by non-uniform asperity damage and the resulting gouge that accumulates on their interfaces. Therefore, an attempt has been made in this study to predict the complete shear behaviour of rough joints incorporating the asperity deformation under CNS conditions. In order to validate this analytical model, a series of CNS shear tests were conducted on rough tensile (natural) joints and their replicas at a range of initial normal stresses that varied from 0.4 to 1.6 MPa. Comparisons between the predicted shear behaviour and the experimental results show close agreement.
Numerical modelling of cyclic shear behaviour of rock joints under constant normal stiffness condition
2013
The cyclic shear behaviour of rock joints was investigated in the laboratory under constant normal stiffness condition for low and high values of initial normal stress and asperity angle. The Universal Distinct Element Code was applied (UDEC) to simulate the laboratory behaviour using two available models. The predicted shear stress, normal stress, and dilation with shear displacement were compared with experimental results. It was observed that the change in the shear strength and recovery of dilation upon load reversal are simulated using the Coulomb Slip model for low values of initial normal stress and asperity angle when the shearing mechanism was sliding over asperities. However, the Continuously Yielding model replicated better cyclic shear behaviour of rock joints under breaking mechanism (i.e. high levels of initial normal stress and asperity angle), as this model represents progressive damage of asperities during shearing and approaching to the residual friction angle when asperities are fully degraded.
Shear behaviour of rock joints under cyclic loading
2012
For the design of civil and mining engineering geo-structures, it is often necessary to investigate the behaviour and the role of discontinuities on the rock mass performance. In many cases, failure is governed by the shear behaviour of discontinuities in excavations. In this context, evaluation of the effects of small repetitive earthquakes on the shear strength parameters of rock joints especially in tunnels and dam foundations is also important. This paper presents the results of a systematic study carried out on the cyclic shear behaviour of artificial rock joints under constant normal stiffness (CNS) conditions, as many of the previous studies have been conducted under constant normal load (CNL) conditions. To understand the basic mechanisms involved, idealized joint samples were subjected to cyclic loading using a large scale direct shear apparatus for different stress amplitudes. The mechanisms behind the shearing under cyclic loading at low and high level of normal stresses have been investigated and compared with CNL conditions experiments. The results indicate that asperity sliding and shearing are the two main mechanisms governing the mechanical behaviour of joints under cyclic loading. Moreover, the joint cyclic dilation is overestimated under the CNL conditions.
Modelling the Shear Behaviour of Rock Joints with Asperity Damage Under Constant Normal Stiffness
Rock Mechanics and Rock Engineering, 2014
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Coupled behavior of rock joints
International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 1991
The behavior of rock joints under various coupled processes is reviewed under four broad categories: (1) hydromechanical (HM) processes, (2) thermohydromechanical (THM) processes, (3) hydromechanical-chemical (HMC) processes, and (4) thermomechanical-hydrochemical (TMHC) processes. The state-of-the-art and possible directions of further research in these coupled processes are discussed. Rock joint behaviors considered include not only dilation, closure, shear and joint propagation, but also changes in flow permeability and chemical sorption and retardation capabilities. These properties are of critical concern in practical considerations of the rock mass as a medium to store and isolate chemical and radioactive wastes. Investigations of coupled processes in two-fracture systems and multi-fracture systems are pointed out as interesting areas for future research. The need to-consider coupled processes in borehole testing procedures involving rock joints is emphasized.
Characterization of the parameters that govern the peak shear strength of rock joints
In Switzerland, there is concem that sliding along joints under dams could lead to stability problems. As part of a research project funded by the Swiss Federal Office for Water and Geology, more than fifty constant-normal-load direct-shear tests have been performed on induced tensile fractures for seven rock types. Damage zones are evident on all of the sheared surfaces. There is evidence of both crushing and breaking of surface asperities. Damage is relatively sparse, and the location of the damaged zones is strongly related to geometrical features. However, the relationships between surface roughness, stress distribution, and damage are complicated and difficult to study, in part, because the boundary conditions goreming the mechanical behavior change continuously during shearing. One of the primary objectives of this work is to better understand the micromechanical behavior of joints under shear loads, including the creation of damage zones. This requires understanding the relationships between material properties, surface geometry, contact area, stress distribution, and the creation of damage during shearing. A methodology for predicting damage during shearing has been developed based on analysis of maps of the joint surfaces obtained before and after shearing using a three-dimensional optical system. The surface data is analyzed to identify the areas on the joint surfaces most likely to be in contact during shearing; i.e. areas with positive slope with respect to the shear direction. Ix)cal gradients are also taken into account in predicting those areas of the joint surfaces most likely to be damaged during shearing. The damage predicted is compared to the damage mapped on laboratory test specimens.
B
Barton-Bandis Criterion
Nick Barton
Nick Barton & Associates, Oslo, Norway
Definition
A series of rock-joint behavior routines which, briefly stated,
allow the shear strength and normal stiffness of rock joints
to be estimated, graphed, and numerically modelled, for
instance, in the computer code UDEC-BB. Coupled behavior
with deformation and changes in conductivity is also included
(Barton 2016).
A key aspect of the criterion is the quantitative characterization of the joint, joints, or joint sets in question, in order to
provide three simple items of input data. These concern the
joint-surface roughness (JRC: joint roughness coefficient),
the joint-wall compressive strength (JCS: joint compressive
strength), and an empirically derived estimate of the residual
friction angle (’r). These three parameters have typical
ranges of values from: JRC = 0 to 20 (smooth-planar to
very rough-undulating), JCS = 10 to 200 MPa (weakweathered to strong, unweathered) and jr = 20 to 35
(strongly weathered to fresh-unweathered). Each of these
parameters can be obtained from simple, inexpensive index
tests or can be estimated by those with experience.
The three parameters JRC, JCS, and jr form the basis of
the nonlinear peak shear-strength equation of Barton (1973)
and Barton and Choubey (1977). This is a curved shear
strength envelope without cohesion (c). It will be contrasted
to the linear Mohr-Coulomb “c and j” (with apparent cohesion) criterion later. To be strictly correct the original Barton
equation utilized the basic friction angle jb of flat,
unweathered rock surfaces (in 1973), whereas jr was
# Springer International Publishing AG, part of Springer Nature 2018
P. T. Bobrowsky, B. Marker (eds.), Encyclopedia of Engineering Geology,
https://doi.org/10.1007/978-3-319-73568-9
substituted for jb following 130 direct shear tests on fresh
and partly weathered rock joints (in 1977).
As well as peak and residual shear strength envelopes for
laboratory-scale joint samples, Barton’s cooperation with
Bandis (from 1978) resulted in corrections (reductions) of
JRC and JCS to allow for the scale effect and reduced strength
as rock-block size is increased (Barton and Bandis 1982). The
laboratory-scale parameters, written as JRC0 and JCS0 for
laboratory-size samples of length L0 (typically 50–250 mm),
are written as JRCn and JCSn for in situ rock block lengths of
Ln (typically 250–2500 mm, or even larger in massive rock).
Bandis is also responsible for utilizing JRC and JCS in
empirical equations to describe normal closure and normal
stiffness. Normal stiffness (Kn) has units of MPa/mm and
might range from 20 to 200 MPa/mm. The Barton-Bandis
(B-B) criterion includes the related modelling of physical
joint aperture E (typically varying from 1 mm down to
50 mm, or 0.05 mm) as a result of the normal loading
(or unloading). B-B also includes the theoretically equivalent
smooth-wall hydraulic aperture e (typically 1 mm down
to 5 mm, or 0.005 mm). Usually E > e, and the two are
empirically inter-related, using the small-scale joint roughness JRC0.
Finally the stiffness in the direction of shearing has also to be
addressed. It is called peak shear stiffness (Ks). It has typical
values of 0.1 MPa to 10 MPa/mm, that is, 1/10th to 1/100th of
normal stiffness. The concept of mobilized roughness
(JRCmobilized) developed by Barton (1982) allows both the
peak shear-stiffness and the peak dilation angle (giving an
effective aperture increase with shearing) to be calculated. The
full suite of Barton-Bandis joint behavior figures includes shear
stress-displacement-dilation, stress-closure, and the change of
estimated conductivity in each case. Examples of these are given
in the following diagrams illustrating joint index testing (Figs. 1,
2, 3, 4, 5, 6, 7, and 8) (Barton and Bandis 2017).
50
Barton-Bandis Criterion
TYPICAL ROUGHNESS PROFILES FOR JRC RANGE:
1
0-2
2
2-4
3
4-6
4
6-8
5
8 - 10
6
10 - 12
7
12 - 14
8
14 - 16
9
16 - 18
10
18 - 20
0
50
100 mm
SCALE
Barton-Bandis Criterion, Fig. 1 Top: Four columns of diagrams
showing 1. direct shear tests principles (Note: apply shear force T “inline” to avoid creating a moment), 2. tilt test principles for measuring
JRC0 with jointed-block samples, and fb with drill-core 3. Schmidt
hammer test principles for measuring JCS, and 4. roughness recording
with profile gauge, and a/L (amplitude/length) method for estimating
JRCn at larger scale (Barton 1999). Bottom: Example roughness profiles
and the ten samples with JRC ranges, tilt tests for JRC and jb. (Barton
and Choubey 1977)
Barton-Bandis Criterion
51
τ
τ = σn tan
3
i1
τ
φr
i2
JRC log
i3
i4
(
JCS
σn
φr + i
c
σn
φ
29 r
°
φr °
S 28
JC 2
9
C
JR .9
8
JC
96 S
1.6
σn
JR
16 C
.9
c
τ = σn tan φr + c
τ = σn tan ( φr + i )
Patton
Aplite
Granite
Hornfels
Calc. shale
Besalt
Slate
Gneiss
φr
Mohr - Coulomb
2
2.0
τ = σn tan φr + c
Shear stress (MPa)
1
1.2
0.8
φr
S 6°
2
JC
50
C
JR
0.5
( + φr
0.4
τ
JRC = joint roughness coefficient
0
0
JCS = joint wall compression strength
φr
= residual friction angle
φr
Barton-Bandis Criterion, Fig. 2 Left: Three shear strength criteria
compared: 1. Linear Mohr-Coulomb (with an assumed cohesion intercept c), 2. Bi-linear Patton (j + i) and 3. Continuously curved Barton
formula, termed Barton-Bandis when scale-effects are included. Right:
0.4
1.2
0.8
1.6
Normal stress (MPa)
σn
The peak shear strengths of 130 joint samples, and examples of the
maximum, mean and minimum strength envelopes, with JRC, JCS and
jr values. (Barton and Choubey 1977)
60 mm
JRC60 = 16.1 (mean)
1600
1400
SHEAR FORCE
1200
JRC120 = 13.8 (mean)
120 mm
JRC180 = 10.5 (mean)
180 mm
JRC360 = 9.1
360 mm
1000
800
360mm
180mm
2
1
3
4
600
120mm
400
1
4
60mm
2
5
3
6
9
13
1
14
8
2
15
9
3
16
10
4
6
5
11
12
18
17
200
2
4
6
8 mm
SHEAR DISPLACEMENT
Barton-Bandis Criterion, Fig. 3 One example of the scale-effect studies by Bandis 1980 using replica castings of rock joints, which were direct
shear-tested at different scale. (Effect on JRC greatest for the roughest joints) (Bandis et al. 1981)
B
52
Barton-Bandis Criterion
JRCn
α°
TUFF
1.0
35°
HYDROSTONE
4.2
55°
SANDSTONE
5.5
52½°
CONCRETE
6.0
63°
SANDSTONE
7.4
61°
CONCRETE
8.5
63°
TUFF
9.2
69°
CONCRETE 0
10.7
250
500
70°
SCALE mm
Barton-Bandis Criterion, Fig. 4 Formal allowance for the scale-effect
on JRC and JCS which depends on the block length Ln (in practice the
mean spacing of a crossing set of rock joints) (Barton and Bandis 1982).
Roughness profiles measured on 1,300 mm long diagonally-jointed 1 m3
blocks, with tilt angles (a) and measured JRCn values (Bakhtar and
Barton 1984)
Barton-Bandis Criterion
Barton-Bandis Criterion,
Fig. 5 The JRCmobilized concept
illustrated in the upper diagram
allows shear-strengthdisplacement (and accompanying
dilation and conductivity changes)
to be modelled. This coupled
behavior is modelled in the
distinct element (jointed-media)
code UDEC-BB. (Barton 1982;
Barton and Bandis 2017)
53
B
54
σn= 2 MPa
LABORATORY
TEST
L=0.1 m
3.0
SHEAR STRESS MPa
L=1 m
IN SITU
BLOCK
TEST
2.5
2.0
1
2
3
1.5
ASSUMED
NATURAL
BLOCK SIZE
2 METRES
1.0
0.5
0
1
2
3
4
fr = 30° RESIDUAL
3
2
1
LAB
TEST
IN SITU
TEST
NATURAL
BLOCKS
JRC
JCS
δ PEAK
fr
15
150
1.0
30°
7.5
50
4.0
30°
6.6
40 MPa
6.1 mm
30°
5
7
6
8
9
10
11
12
13
14
15
σn=2MPa
1
2.0
DILATION mm
Barton-Bandis Criterion,
Fig. 6 Shear-displacementdilation behavior, for three
different block sizes. Barton
(1982). Note the inset showing the
scaling assumptions from the
Bandis et al. (1981) equations
given in Fig. 3. Note increase in
dpeak as block size increases. Since
there is also a reduction in peak
shear strength, the peak shear
stiffness Ks suffers a double scaleeffect as block-size increases
Barton-Bandis Criterion
1.5
IN SITU BLOCK TEST
2
1.0
L = 1m
LABORATORY
TEST
3
L = 0.1m
0.5
ASSUMED
NATURAL
BLOCK SIZE
2 METERS
0
0
1
2
3
4
5
6
7
8
9
10
11
12
SHEAR DISPLACEMENT mm
13
14
15
Barton-Bandis Criterion
55
B
Barton-Bandis Criterion, Fig. 7 Examples of “coupled” sheardilation-conductivity modelling with the Barton-Bandis modelling
assumptions. When block-size variations are involved (left) the delayed
dilation and therefore delayed conductivity change can be noted. These
curves were produced in 1983 by Bakhtar using a programmable HP
calculator (Barton and Bakhtar1983, 1987) the BB equations by now
assembled in Barton 1982. ONWI and AECL funded work were responsible for the “finalization” of the BB model prior to its programming
(by Mark Christianson of Itasca) into the distinct element code UDECBB. (Barton and Bakhtar 1983, 1987), using (see also Barton and Bandis
2017)
56
Barton-Bandis Criterion
Barton-Bandis Criterion, Fig. 8 The nonlinear modelling of joint
closure by Bandis (1980) and Bandis et al. (1983). The three loadunload cycles are designed to mirror the experimental evidence of a
large hysteresis on the first cycle due to the unavoidable effects of taking
a (drill-core) sample which releases the original in situ normal stress.
The first load cycle re-closes the joint. The properly consolidated
(cycle 3) behavior is incorporated in the distinct-element (jointed) code
UDEC-BB
Cross-References
References
▶ Mohr-Coulomb Failure Envelope
▶ Rock Mass Classification
▶ Shear Strength
Bakhtar K, Barton N (1984) Large scale static and dynamic friction
experiments. In: Proceedings of 25th US rock mechanics symposium. Northwestern University, Evanston
Beach Replenishment
Bandis S (1980) Experimental studies of scale effects on shear strength,
and deformation of rock joints. PhD thesis, Department of Earth
Sciences, University of Leeds
Bandis S, Lumsden A, Barton N (1981) Experimental studies of scale
effects on the shear behaviour of rock joints. Int J Rock Mech Min Sci
Geomech Abstr 18:1–21
Bandis S, Lumsden AC, Barton N (1983) Fundamentals of rock joint
deformation. Int J Rock Mech Min Sci Geomech Abstr
20(6):249–268
Barton N (1973) Review of a new shear strength criterion for rock joints.
Eng Geol 7:287–332. Elsevier, Amsterdam. Also NGI Publ. 105, 1974
Barton N (1982) Modelling rock joint behaviour from in situ block tests:
implications for nuclear waste repository design. Office of Nuclear
Waste Isolation, Columbus, 96 p, ONWI-308, Sept 1982
Barton N, Bakhtar K (1983) Description and modelling of rock joints for
the hydrothermomechanical design of nuclear waste vaults, vols I
and II (unpublished). CANMET, Ottowa. Contract report from Terra
Tek, Salt Lake city
Barton N, Bakhtar K (1987) Description and modelling of rock joints for
the hydrothermalmechanical design of nuclear waste vaults, vols I
and II. Atomic Energy of Canada Limited. TR-418
Barton N (1999) General report concerning some 20th century lessons
and 21st century challenges in applied rock mechanics, safety and
control of the environment. In: Proceedings of 9th ISRM congress,
Paris, vol 3. Balkema, pp 1659–1679
Barton NR (2016) Non-linear shear strength descriptions are still needed
in petroleum geomechanics, despite 50 years of linearity. In: 50th US
rock mechanics. Houston. ARMA 16, paper 252, 12 p
Barton N, Bandis S (1982) Effects of block size on the shear behaviour of
jointed rock. Keynote lecture, 23rd US symposium on rock mechanics, Berkeley
Barton NR, Bandis SC (2017) Chapter 1. Characterization and modelling
of the shear strength, stiffness and hydraulic behaviour of rock joints
for engineering purposes. In: Feng X-T (ed) Rock mechanics and
engineering, vol 1. Taylor & Francis, pp 3–40
Barton N, Choubey V (1977) The shear strength of rock joints in theory
and practice. Rock Mech 1/2:1–54. Springer, Vienna. Also NGI Publ.
119, 1978
Barton N, Bandis S, Bakhtar K (1985) Strength, deformation and conductivity coupling of rock joints. Int J Rock Mech Min Sci Geomech
Abstr 22(3):121–140
Beach Replenishment
D. E. Reeve and H. Karunarathna
University of Swansea, Swansea, UK
Synonyms
57
What Is Beach Replenishment?
Beach replenishment is the placement of beach material,
usually sand, on a beach in order to increase the beach volume
(Dean 2002; Kamphuis 2010; Reeve et al. 2011). It is used as
a component of flood defense to absorb/dissipate incoming
wave energy or in coastal protection schemes to counter longterm erosion. Current practice is to use material of color, size
distribution and type as close to the natural local material as
possible. In many open coast situations, beach replenishment
forms part of a larger flood defense or coastal protection
scheme that includes hard structures such as groins (Coastal
Engineering Manual 2008).
When Is Beach Replenishment Carried out?
Many of the world’s beaches are now actively managed,
which will often include monitoring the beach width, levels,
and composition. Many responsible authorities will have set
criteria, such as a minimum beach level they are willing to
tolerate, which act as a “trigger” to commence a replenishment.
Where Is the Material Placed?
There are several options for the placement of replenishment
material: at the top of the beach where it acts as a store of
material accessed only during storms, across the beach profile
to replicate a natural beach, and at the bottom of the active
profile where it may be moved onshore during quiescent
periods to build up the entire beach profile.
How Is the New Material Deposited on the Beach?
Replenishment at the top of the beach is often the cheapest
option as it is a land-based operation. Material will need to be
brought to the beach location and shaped to the desired form
with bulldozers (Fig. 1). Distribution across the profile is
normally achieved with a dredger “rainbowing” a slurry of
sand and seawater onto the beach during low tide where it
drains and can be shaped using bulldozers. Placement at the
base of the beach is usually performed using a bottom-opening
barge discharging at high water to avoid the vessel grounding.
Beach nourishment
Latest Developments
Definition
The process of adding sediments to a beach in order to replace
material that has been removed by the continuing physical
action of waves and tides over a period of years.
Beach replenishment is a continuing process and might, for
example, involve adding material once every 5–10 years over
the course of a 50-year project. This can make replenishment a
more expensive option due to the mobilization costs involved in
repeated placement of material. These costs have prompted the
B
58
Bearing Capacity
Beach Replenishment,
Fig. 1 Beach replenishment at
Herne Bay, UK (With
acknowledgments to Claire
Milburn, Canterbury City
Council)
idea of “mega-nourishments,” whereby extremely large volumes of material (in excess of 20 million m3) are deposited in
a single phase, thereby incurring only one set of mobilization
costs Sand Engine web. The addition of this amount of sediment
to a beach represents a major perturbation and may alter the
prevailing morphodynamic conditions, which is the topic of
ongoing research.
Cross-References
▶ Coastal Environments
▶ Erosion
▶ Floods
▶ Nearshore Structures
Bearing Capacity
Jeffrey R. Keaton
Amec Foster Wheeler, Los Angeles, CA, USA
Definition
Bearing capacity is the maximum stress or pressure that a
footing can sustain without failure of the soil or rock that is
supporting the footing. Bearing capacity is a function of the
shear strength of the soil material or rock mass, but it also
depends on the size and shape of the footing and the thickness
of soil or rock adjacent to and above the base of the footing.
Context
References
Coastal Engineering Manual (2008) Available online at: http://www.publi
cations.usace.army.mil/USACE-Publications/Engineer-Manuals/?udt_
43544_param_page=4
Dean RG (2002) Beach nourishment: theory & practice, advanced series
on ocean engineering, vol 18. World Scientific, Singapore
Kamphuis JW (2010) Introduction to coastal engineering and management, advanced serieson ocean engineering, vol 16, 2nd edn. World
Scientific, Singapore
Reeve DE, Chadwick AJ, Fleming CA (2011) Coastal engineering:
processes, theory and design practice, 2nd edn. Spon Press, London/New York
Sand Engine web site.: http://www.dezandmotor.nl/en/the-sand-motor/
introduction/
Bearing capacity is a soil–structure interaction phenomenon.
Typically, it is associated with foundations of buildings, which
is the domain of structural and geotechnical engineers. Engineering geologists provide valuable site characterization details
pertaining to the nature and uniformity or variability of subsurface earth materials, as well as the geohazards that might
affect site suitability or represent constraints that require design
provisions or mitigation by ground improvement prior to
construction.
For buildings supported on shallow foundations (spread
footings), the weight of the building is calculated by the
Bearing Capacity
structural engineer and proportioned to the walls and columns
that provide the structural support system for the building. Walls
are supported by spread footings that extend under the entire
length of the wall (continuous spread footings). Columns are
supported by isolated spread footings. In some cases in which a
shallow foundation are determined to be suitable for structural
support, but building performance needs to be enhanced for rare
events, such as earthquake shaking, foundation systems may be
enhanced by tying isolated spread footings together with grade
beams. Grade beams are reinforced concrete elements that are
not relied upon to contribute to vertical load-bearing capacity of
a building’s foundation system, but act as structural elements
that add stiffness to transform isolated spread footings into a
connected network of spread footings.
In certain geologic settings (for example, Holocene marine
clay deposits) or for very heavy foundation structural loads
(tall buildings) or for facilities that generate strong ground
vibrations (reciprocating compressors), shallow spread footings would have insufficient capacity or would result in
intolerable settlement of the building because of consolidation of clayey Earth materials. Deep foundations (shafts or
piles) are used to transfer loads deeper into the soil profile to a
strong layer or to a depth sufficient for the load to be distributed along the length of a shaft or pile. Deep foundations have
bearing capacities which are derived mostly from friction or
adhesion of soil along the sides of the foundation elements,
with typically small contribution of bearing at the ends of the
shafts or tips of the piles.
Geotechnical engineers use shape factors to account for the
stress distribution differences associated with footings of different shapes that bear on soil layers that are suitable to
support the structural loads. Shallow footings may be isolated
or continuous for columns or walls and have widths that are
designed for the bearing capacity of the soil. The base of the
shallow footing may bear on soil less than 1 m below the
Bearing Capacity, Fig. 1 Cross
section of a general shear failure of
an isolated shallow spread footing
in response to a load P that
exceeded the bearing capacity of
the foundation soils. Geometry of
general failure surface for
Terzaghi’s bearing capacity
formulas is discussed in Coduto
et al. (2016)
59
ground surface adjacent to the footing, or it may be designed
to bear on soil several meters below the ground surface. The
ultimate bearing capacity is the maximum load that can be
applied on a footing of specified dimensions that approaches,
but does not exceed, the calculated soil shear strength. Variabilities in soil properties across the footprint of a building and
uncertainties of temporary loads caused by wind and earthquakes are managed with an engineering approach called
“factor of safety,” which is the ratio of the soil’s shear strength
to the expected stress transmitted to the soil at the base of the
footing. The geotechnical engineer’s best estimate of soil shear
strength is used with information from the structural engineer
and footing shape factors and embedment depths to calculate
the ultimate bearing capacity of the foundation soil. The
ultimate bearing capacity is divided by the factor of safety,
commonly 3 or higher for foundation engineering, to calculate
allowable bearing capacity.
Three types of shallow bearing capacity failure can occur:
general shear failure, local shear failure, and punching shear
failure. Foundation failures typically are rare, but general
shear failures (Fig. 1) are relatively more common than the
other types. General shear failure results from development of
a shear surface below the footing that extends to the ground
surface and produces distinctive bulging of the soil. Local
shear failure results from consolidation or compaction of soil
under a footing in a way that a shear surface is well defined
near the footing, but shearing becomes distributed away from
the footing; bulging of soil on the ground adjacent to the
footing is noticeable. Punching shear failure results from a
geotechnical condition of a relatively strong surface soil layer
that forms a crust over a weak soil layer; the structural load
essentially pushes the footing and strong soil into the underlying weak soil layer, causing consolidation or compaction of
the weak soil without noticeable bulging at the ground.
B
60
Bedrock
One type of bearing capacity that involves rock materials
is support of pillars in room-and-pillar mines, such as used
in some coal mines (Darling 2011). In these cases, engineering geologists or geological or mining engineers measure in situ stresses and calculate lithostatic stress that
would need to be carried by the pillars. The rock comprising the floor of the mine would be the foundation material
for the pillars that act as columns in the structural support
system of the mine. Pillars that are too small in crosssection area tend to have stress concentrations that exceed
the strength of the rock in the pillar, as well as exceed the
bearing capacity of the rock in the mine floor. In coal
stratigraphy, a common bottom-to-top sequence might
be sandstone-siltstone-claystone-shale-coal-sandstone. The
coal formation would comprise the pillars, whereas the
claystone-shale would comprise the foundation material.
Coal tends to be brittle with a relatively low Poisson’s
ratio and claystone-shale may be relatively weak, particularly if it becomes saturated.
Cross-References
▶ Angle of Internal Friction
▶ Consolidation
▶ Factor of Safety
▶ Foundations
▶ Liquefaction
▶ Poisson’s Ratio
▶ Pore Pressure
▶ Pressure
▶ Shear Strength
▶ Site Investigation
▶ Soil Field Tests
▶ Soil Laboratory Tests
▶ Soil Properties
References
Coduto DP, Kitch WA, Yeung MR (2016) Foundation design: principles
and practices, 3rd edn. Pearson, New York
Darling P (ed) (2011) SME mining engineering handbook, 3rd edn.
Society for Mining, Metallurgy, and Exploration, Englewood. Available from http://www.smenet.org/. Accessed May 2016
Bedrock
Mihaela Stãnciucu
Department of Engineering Geology, Faculty of Geology and
Geophysics, University of Bucharest, Bucharest, Romania
Definition
Bedrock consists of “soils and rocks that were in place before
the Quaternary Period” (British Geological Survey 2011).
This definition may be classified as “a stratigraphical
criterion”.
The concept of bedrock in geosciences has, despite it’s
apparent simplicity and worldwide use, different meanings
accordingly to the different fields of activity in which it is
applied. Thus, all magmatic, metamorphic or sedimentary
rocks, beside sedimentary soils older than about two million
years, exposed at the Earth’s surface (outcrop) or overlain by
unconsolidated deposits form the bedrock of a region. But,
sometimes, a sedimentary layer from the Quaternary Period,
may be classified as bedrock if it was subjected to tectonic
stress, reflected in visible folds or faults and lithification. It is
appropriate to apply this second “tectonic criterion” in seismic regions, where tectonic stress is still active (Florea 1969).
In contrast, unconsolidated Quaternary deposits, as alteration products of bedrock, residual soils, regoliths or saprolites,
are distributed over bedrock in different geomorphologic features and formations (alluvial, diluvial, or colluvial) and are
defined as “shallow or surficial deposits” (see Fig. 1).
Bedrock, Fig. 1 Superficial
deposits resting on bedrock (After
Florea 1969)
Superficial deposits
Alteration of
(Quaternary Period)
bedrock
Dilluvial
Colluvial
Bedrock
(Pre-Quaternary Period)
Alluvial
Biological Weathering
The basic distinction between bedrock and surficial
deposits is applied in engineering geology when acquiring
qualitative information regarding soil properties, prior to the
execution of geotechnical in situ or laboratory tests and is
most relevant if we compare mechanical properties of soils
of similar kinds. For instance, clay soils in bedrock formations (e.g., terrace formations of the Tertiary Period) tend to
be normal to overconsolidated and have low compressibility
in contrast to clay soils formed as surficial deposits (e.g.,
alluvial plains of the Quaternary Period) which are usually
underconsolidated with high or very high compressibility.
From the civil engineering point of view, bedrock or
engineering rockhead define the rock or soil that has adequate bearing capacity for large structures. Quantitative
criteria for differentiation of shallow and bedrock deposits
are very variable reflecting the state of professional practice
and regulations in the region concerned. The most widely
used tests are Standard Penetration Tests for soils and Rock
Quality Designations and unconfined compressive strength
for rocks.
In earthquake engineering the term “bedrock” is used to
define two limits of the geological structure based on the
shear wave velocities. The upper limit named “engineering
bedrock” is defined by Vs> 700 m/s dividing the shallow
deposits from the bedrock. The deeper limit, called “seismic
bedrock”, is defined by Vs> 3000 m/s and marks the upper
interface of the upper Earth crust (Nath 2007).
Bedrock maps reflect the distribution of rock units,
their geometric relationships, tectonic setting, as the origin
of each unit and may be produced as base research maps
for engineering projects, soil chemistry, natural plant ecology, water supply, contaminant transport issues, or other
purposes.
Cross-References
▶ Classification of Rocks
▶ Earthquake
▶ Geophysical Methods
▶ Rock Mechanics
References
British Geological Survey (2011) Engineering geology (bedrock) map of
the United Kingdom. British Geological Survey, Keyworth
Florea MN (1969) Bedrock and shallow deposits, vol XVII. Bulletin of
Oil, Gas and Geology Institute, Bucharest
Nath SK (2007) Seismic microzonation framework – principles & applications. In: Proceedings of workshop on microzonation. Indian Institute of Science, Bangalore, pp 9–35
61
Biological Weathering
Maria Heloisa Barros de Oliveira Frascá1 and
Eliane Aparecida Del Lama2
1
MHB Geological Services, São Paulo, SP, Brazil
2
Institute of Geosciences, University of São Paulo, São Paulo,
SP, Brazil
Synonyms
Biodeterioration;
organisms
Organic
weathering;
Weathering
by
Definition
Mineralogical components of rocks are altered and modified
when exposed to Earth surface conditions in response to different atmospheric agents and insolation that may result in the
disaggregation (physical weathering) or the decomposition
(chemical weathering) of the rock. When these processes are
assisted by biologic action they are called biological weathering.
Organisms may alter rock by both mechanical and chemical actions. The penetrating and expanding pressure of plant
roots in cracks, fractures, pores and other discontinuities may
cause the rupture and disaggregation of the rock, if there are
favorable conditions and the strength of the rock is lower than
that applied by the roots (Fig. 1). Penetration and expansion
of lichen thalli has a similar behavior to that of the roots since
some thalli may expand up to 3900 per cent due to their high
content of gelatine (Bland and Rolls 1998).
Organic activity, mainly caused by microscopic organisms as
bacteria, fungi, lichens, mosses, algae, etc. and also by animals,
plays an important role in the decomposition of the rock. Attack
is by chemical means, with the segregation of compounds as
CO2, nitrates, and organic acids as metabolic products, resulting
eventually in the total alteration of the rock and soil formation.
The presence of water is essential to enable the growth of
microorganisms and plants. Production of CO2 and organic acids
and nitrification increase the dissolution capacity of soil water.
Heavy metals (copper and zinc or even metal alloys, such
as bronze) may inhibit biological growth.
An overview of biological weathering is presented in
Yatsu (1988) where the general aspects and the contribution
of microorganisms, plants, and animals are described.
Biological weathering is also observed in natural stone used
for buildings and monuments (Caneva et al. 2009) where the
damage caused by microorganisms depends on the species,
fixation mode, and rock type, as well as the local climate,
degree of pollution, maintenance, and other anthropogenic
factors. In this case, the term biodeterioration is applied,
which is the physical, chemical, and/or biological damage
B
62
Blasting
Biological Weathering,
Fig. 1 Example of biological
weathering by growth of tree roots
in granite
effected by organisms on an object of historic, cultural, artistic,
or economic importance (Griffin et al. 1991). Hueck (2001)
defines biodeterioration as any undesirable change in the properties of materials caused by the vital activities of organisms.
References
Bland W, Rolls D (1998) Weathering: an introduction to the scientific
principles. Arnold, London, 271 p
Caneva G, Nugari MP, Salvadori O (2009) Plant biology for cultural
heritage: biodeterioration and conservation. Getty Publications, Los
Angeles, 400 p
Griffin PS, Indictor N, Koestler RJ (1991) The biodeterioration of stone:
a review of deterioration mechanisms, conservation, case histories
and treatment. Int Biodeterior 28:187–207
Hueck HJ (2001) The biodeterioration of materials – an appraisal. Int
Biodeter Biodegr 48:5–11
Yatsu E (1988) Weathering by organisms. In: The nature of weathering:
an introduction. Tokyo, Sozosha, pp 285–396
Blasting
Gregory L. Hempen
EcoBlast, LC, St. Louis, MO, USA
Definition
Controlled blasting is the carefully designed and successive
placement of explosives with timed sequences of detonations
to safely excavate low-tensile strength materials to a defined
surface. It may be utilized to conduct rapid removals of materials, while minimizing the risk of varied adverse impacts.
Blasting is an effective procedure, because chemical
energy of the explosives is rapidly used to perform work.
Two techniques utilize this rapid energy release: controlled
blasting of low-tensile strength materials (rock and concrete)
to be fractured and displaced to more easily processed sizes;
and severance of metal frameworks, which deploys linear
shaped charges detonated at discrete locations allowing the
framework to be dismantled and displaced.
The performance of blasting and the potential risk of
adverse impacts for both of these techniques are determined
by several parameters, and confinement of the explosive
charges is a major factor. Controlled blasting confines the
charge to allow the rapid expansion of the detonation
products’ gases to perform work. Severance of steel framing
is conducted without confinement of the linear shaped
charges; this technique will not be further reviewed.
All uses of explosives must be carefully designed, because
blasting is inherently destructive and may adversely affect surrounding assets. Controlled blasting is employed, since it is
more rapid and cost-effective than mechanical means of excavation or demolition. The primary blasting impacts of air blast
(noise), fly-rock (thrown projectiles), underwater overpressure
(pressure wave passage through water), and ground vibration are
dependent upon the shot pattern parameters, ambient geology
and weather conditions, and surrounding built environment.
There are several secondary impacts due to blasting.
Blasting projects assess environmental impacts, which in the
blasting industry is considered to be only protecting the nearby
public or structures. There may be insufficient evaluation of
other secondary impacts: sensitive features of certain equipment within buildings or historic and archeological elements;
natural resources; and, induced geologic hazards. Naturalresource impacts are those adversely acting upon flora and
fauna that have commercial value or are threatened or endangered species. In the USA, natural-resource impacts are often
prescriptively assessed under environmental regulations. Several geologic hazards may be induced or triggered by the
primary impacts of blasting or may result from the physically
excavated or demolished removals. These induced geologic
hazards may include: soil displacement toward the removed
Borehole Investigations
63
Blasting, Table 1 Comparative performance and risks from controlled blasting
B
material, slope instability, karst collapse, changes of the
ground-water flow, and liquefaction/lateral spreading.
Any project, which may involve blasting, should assess
whether any adverse impacts may occur before developing
contract specifications. Owners need to be informed of the
assessed risks from both primary and secondary blasting
impacts. Additional insights related to blasting can be found
in: Keevin and Hempen 1997, Hempen 2008, California
Department of Transportation 2017, Skeggs et al. 2017, and
US Army Corps of Engineers (in press).
Table 1 notes the approximate likelihood of meeting a
project’s objectives and of varied impacts. The location
of the blasting on land or beneath water and the confinement
of the explosives forecast the blasting’s performance and
risks of impacts. Contract-specified test blasting programs
require the cautious development of explosive weights,
which may be increased with successive, acceptable shot
patterns to the final blasting design. Adequate confinement
and good performance with low risk of adverse impacts may
be developed under a sequential test blasting program.
References
California Department of Transportation (2017) San Francisco-Oakland
Bay Bridge (SFOBB), East Span Seismic Safety Project, SFOBB Old
Spans Piers E3-E5 Implosions Project Report, EA 04-01357 or
EFIS#: 04-16000287, 141 p with appendices
Hempen GL (2008) Destructive water-borne pressure waves. Proceedings of the sixth international conference on case histories in geotechnical engineering, Arlington, VA, Missouri University of Science
and Technology, Rolla, MO, 11 p
Keevin TM, Hempen GL (1997) The environmental effects of underwater explosions with methods to mitigate impacts, legacy report
(Department of Defense study grant). U.S. Army Corps of Engineers,
St. Louis, 145 p
Skeggs D, Lang G, Hempen G, Combs R, Clemmons M (2017) Controlled blasting for CCP landfill construction, world of coal ash
conference, landfill session V, paper 206, Lexington KY, 11 p
US Army Corps of Engineers (in press, expected February 2018) Systematic drilling & blasting for surface excavations, EM 1110-2-3800,
Washington, DC, 260 p & 2 appendices
Borehole Investigations
Eduardo Kruse1, Saeid Eslamian2, Kaveh Ostad-Ali-Askari3
and Sayedeh Zahra Hosseini-Teshnizi2
1
National Research Council La Plata National University
Argentina, La Plata, Buenos Aires, Argentina
2
Department of Water Engineering, Isfahan University of
Technology, Isfahan, Iran
3
Department of Civil Engineering, Isfahan (Khorasgan)
Branch, Islamic Azad University, Isfahan, Iran
Synonyms
CPT sample; Drill hole study
Definition
Method of study to investigate soils and rocks in the Earth’s
subsurface by means of long and narrow holes drilled using a
variety of specialized methods.
64
Introduction
Successful engineering works often benefit from a clear and
better understanding of the nature of soil and rock below
ground. In the absence of extensive trenching and excavation
and to complement non-invasive geophysical exploration
techniques, borehole investigations can be carried out, including the analysis and characterization of the soil and rock
recovered. Such investigations allow the identification of the
soils or rocks present, as well as an understanding of their
physical properties on the basis of field and laboratory tests.
Borehole investigations allow practitioners to determine
the nature and location of the different soil/rock layers, collect
samples, carry out in situ tests and permeability tests, and, if
necessary, install piezometers and other subsurface monitoring tools. The location of the boreholes is chosen depending
on the objective of the project and characteristics of the tests,
with due consideration to the type of works planned.
Borehole Investigations
In rotary core drilling, a rock cylinder referred to as “core”
may be extracted as the drilling advances and stored in a pipe
screwed to the crown, which is called a “core barrel.” This
may be a simple tube or a rotating double tube in which the
inner tube is mounted on bearings.
In the case of loose or very soft soils, a simple tube must
be used, whereas a rotating double tube is preferable in all
other cases. A casing pipe is introduced into the borehole to
prevent cave-ins or stop water leaks; the casing is telescopic
and allows the insertion of the core barrel to continue drilling.
The exterior diameter of normalized boreholes ranges
between 54 and 143 mm.
Borehole investigations for different civil engineering
works must be approved by local state agencies, complying
with requirements usually determined by ASTM standards or
similar specifications.
Sampling
Borehole Systems
Boreholes may be drilled by two primary systems: percussion
or rotary techniques. The former relies on the use of a tool
that advances with successive hitting movements, driven by a
hammer that is dropped, with its energy transmitted by means
of rods to a solid tool or hollow tube (sampler) placed at the
bottom of the borehole. This system, which has advantages in
unconsolidated soils (silt, sand and gravel), usually takes longer and is more expensive than rotary drilling. The rotary
technique (Fig. 1) is the most frequently used method for
subsurface exploration. A cutting tool is used to collect samples
using a helical auger or drill bit that moves forward by means of
a bit crown that is usually WIDEA or diamond tipped.
In the case of auger drilling, alternative methods
are needed to obtain samples, which is normally carried
out discontinuously. This technique is mainly used in
uncemented soft to medium consistency soils or in rocks.
Samples are representative portions of the soil/rock that
are collected for visual examination or to conduct laboratory
tests. Depending on the means of collection, they may be
classified as disturbed or undisturbed samples (USDA 2012).
Disturbed samples only preserve some of the soil/rock
properties in their natural state and are usually stored in bags
or as core segments. Undisturbed samples preserve, at least in
theory, the same properties as the in situ soil, reflecting the soil/
rock characteristics in their natural state at the moment of
collection and, consequently, their physical structure.
In order to undertake laboratory tests, it is necessary to
collect undisturbed samples, which are obtained by means
of core barrels from the boreholes. Once the core barrel has
been extracted, the core within is retrieved and placed in a
core box. After the collected core is laid out, it is visually
inspected and the recovery obtained is measured.
Core samples must be placed in adequate core boxes made of
wood or waxed cardboard, maintaining the original position and
Borehole Investigations, Fig. 1 Rotary system of drilling in unconsolidated sediments
Borehole Investigations
orientation, and indicating the depth. For this operation to be
properly carried out, the same sequence in which the samples
were obtained must be followed, introducing separation blocks
between the different core runs and defining sampling depths.
As well as the core recovery percentage, the rock-quality
designation (RQD) of all the core samples obtained is determined (Deere and Deere 1988). This index, expressed as a
percentage, is defined as a quotient between the sum of the
length of the core pieces and the total length of the core run.
There are different tools for the collection of samples, and
depending on their characteristics, disturbed or undisturbed
samples will be obtained. The use of a Shelby tube sampler is
preferred in cohesive silty and clayey soils, whereas a splitspoon sampler is used in sandy soils (Small 2016).
A sample extracted by means of a hand or machine-driven
auger consists of a short cylinder that is obtained from the
combination of rotation and downward force. Samples collected in this manner are regarded as disturbed.
Undisturbed soil samples may be collected by means of
thin-wall coring tubes that are pushed into the ground. Thickwall coring tubes are driven into the soil with a hammer in
order to collect soil samples with some cohesion. The sample
within the tube is a representative sample, but it is not considered undisturbed.
In order to avoid dropping the sample from the tube due to
the thrust of water when operating below the water table, a
valve is located at the top of the sampler and it is seated on
the head of the tube to prevent the water from descending and
putting pressure on the sample. It is a simple, robust sampler
whose greatest disadvantage is that the sample must be
pushed to extract it from the tube, which subjects it to a certain
degree of deformation.
The Shelby tube sampler is very simple and widely used.
It consists of a thin-wall tube, generally made of steel, with a
sharp cutting edge. The disadvantage of this type of sampler is
that it is necessary to push the sample out of the tube, which
causes some disturbance.
Borehole Investigations,
Fig. 2 Water samples and water
table measurement
65
Stationary-piston samplers avoid the penetration of mud
or prevent the water pressure from affecting the sample as
water enters the tube and raises the ball when discharging the
water towards the rods. They may be used in soft to moderately stiff clayey soils and in loose sand.
A double-tube soil core barrel has a core lifter that protrudes some 4–9 cm from the crown, which ensures that
the drilling fluid will not reach the sample and that the
crown will not come into contact with the core. It may be
used in clayey soils of hard consistency and the quality of the
samples obtained is regular to good depending on the ground
conditions.
When the soils are cohesive and their resistance is high,
the collection of an undisturbed sample is substituted by
dipping in paraffin the longest section of the core obtained.
These sections, once they have been superficially cleaned,
must be covered in non-absorbent material and everything
must be protected with a paraffin wax seal thick enough to
ensure there are no variations in the humidity conditions.
Water samples are collected from boreholes to study the
hydrochemical characteristics of the water found in the survey
points. It is common to keep a record of the water table level in
every borehole (Fig. 2), not only during the drilling but also once
it has been completed, at least until the end of the field work.
If bentonite drilling muds or special drilling gels are used
during the drilling, the boreholes must be cleaned once they
have been completed by means of clean water circulation.
Bentonite drilling muds or special gels must be used with
caution, especially if the objective is to subsequently carry out
permeability tests.
Should it be necessary, or convenient, piezometers may be
installed so as to isolate the different aquifers intersected by
each borehole.
Every sample and core must be appropriately packed to
avoid alterations during transport or storage, and must
be shipped as soon as possible to the laboratory. Undisturbed
samples must be preserved in a laboratory environment with
B
66
controlled temperature and humidity. Only the packages with
the samples that are going to be tested should be opened, and
not until the moment when the corresponding tests are going
to be carried out.
Borehole Testing
The main tests undertaken in situ in a borehole are as follows:
Standard Penetration Test (SPT)
The SPT is the most common test among those conducted
within a borehole (Price 2009). It is a simple test and it may
be performed while the borehole is being drilled. It may be
applied to any type of soil, including soft or weathered rocks.
It is possible to correlate the SPT with the mechanical soil
Borehole Investigations,
Fig. 3 Standard penetration test
Borehole Investigations
parameters; this correlation, together with the data obtained
from laboratory tests, helps define the allowable pressure of a
soil for a specific type of grouting.
The SPT is an in situ dynamic penetration test designed to
obtain information on the soil properties, while it also collects
a disturbed soil sample to analyze grain size and determine
soil classification.
The SPT N-value is defined as the number of blows
required to achieve a penetration of 45 cm with a sampler
placed in the lower portion of the drive rods. It is driven into
the ground by means of a 63.5 kg (140 lb) hammer that is
dropped in free fall on the top end of the drive rods from a
height of 76 cm (30 inches) (Fig. 3).
Usually, the sampler has an outside diameter of 2 inches and
an inside diameter of 13=8 inches; in the case of gravel, a conical
tip with a diameter of 2 inches and an apex angle of 60 is used.
Borehole Investigations
67
As a hollow tool is used, the test makes it possible to
collect a disturbed sample of the soil in which the penetration
test was carried out, so as to analyze in the laboratory.
Pressuremeter and Dilatometer Tests
These are stress-strain tests undertaken directly in the soil in
order to identify its geotechnical characteristics, regarding its
deformability (pressuremeter modulus) and resistance properties (limit pressure).
They are conducted by the expansion with gas of a cylinder
cell against the walls of a borehole, measuring the volumetric
deformation of the soil in a horizontal plane corresponding to
each pressure until eventually the soil yields.
Regardless of the problem posed by the transformation of the
results obtained in the horizontal measurements in the case of
the reaction of the foundations, which are usually vertical, and
of the fact that soils tend not to be isotropic but heterogeneous,
these tests provide isolated and, therefore, discontinuous data as
regards the layers encountered. The guidelines to conduct this
test are set out in the ASTM D 4719-87 standard.
Permeability Tests
In situ permeability tests are conducted in soils and rocks.
The most common ones consist of the addition or extraction
of water, under a constant or variable hydraulic head.
A reliable estimation of the permeability coefficient is
possible in surveys that detect the occurrence of the water
table and in boreholes in which this coefficient ranges from
10 3 to 10 5 cm/s. In the case of lower permeabilities, it is
necessary to resort to pumping or laboratory tests.
The most frequent ones are referred to as the Lefranc and
Lugeon tests (Monnet 2015).
The Lefranc test is carried out within a borehole, during
the drilling or once it has been completed. This test estimates
the permeability coefficient k in granular soils (gravel, sand,
and silt) or in highly fractured rocks occurring below the
water table. It is performed by filling the borehole with
water and measuring the necessary flow to maintain a constant level (constant-head) or the fall velocity (variable-head).
In the constant-head test, as a general rule, the inflow rate is
measured at specific time intervals, keeping a constant level at
the borehole head. The k coefficient of the section is the
average of all the values obtained. The variable-head test is
preferably conducted downward, starting from a maximum
head of water and recording the decrease in water level within
the pipe at different times.
The Lugeon test consists of injecting water under pressure
at an isolated section of a borehole bounded by one or two
packers and measuring the amount of water that infiltrates into
the soil (Fig. 4).
This test can be carried out as the borehole is being drilled or
once it is completed. First, the section to be tested is chosen.
Once the packers are in place, the injection of water begins,
B
Borehole Investigations, Fig. 4 Lugeon test
measuring the volume of water injected. The measurement is
performed at certain intervals, starting with a minimum pressure and increasing this in stages, all the while measuring the
volume of water intake. Starting from the maximum pressure,
the same process is repeated but decreasing the pressure at each
stage, until the initial pressure is reached. Water is injected by
means of a pump, measuring the pressure with a gauge and the
volume injected with a flowmeter.
This test is applied to medium to low permeability consolidated soils or rocks (10 6 < K < 10 9 m/s).
Different tests can be performed in the laboratory, which
makes it possible to measure a wide variety of soil properties.
Some of these properties are intrinsic to the composition of
the soil matrix and they are not affected by the disturbance of
the sample, whereas other properties depend on the structure
and composition of the soil, and these can only be analyzed
effectively in relatively undisturbed samples.
Besides geologic logs from drill holes, a suite of geophysical logs can be collected to provide additional information regarding the nature and distribution of materials below
the ground surface. Typical data collected in this manner
comprise spontaneous potential (SP), resistivity, gamma ray,
gamma-gamma, radioactive neutron, and other methods
(acoustic, camera televiewer, etc.)
Summary
The direct study methods used in engineering geology are
based on geotechnical surveys, which allow for the sampling
of subsurface materials and the undertaking of in situ tests.
Boreholes are drilled by percussion or rotary techniques,
with the latter being the most common. Different types of
68
tools are available to obtain disturbed and undisturbed samples. Undisturbed samples are those that best maintain the
physical structure and properties of the soil and lead to more
reliable laboratory test results.
Tests undertaken in situ in a borehole include penetration
tests, pressuremeter and dilatometer tests, and permeability
tests. All of these, together with the ones performed in the
laboratory on the samples obtained from the boreholes, are
essential to understand the characteristics of the soil and to
design engineering works to be constructed at the study site.
Cross-References
▶ Atterberg Limits
▶ Bedrock
▶ Boreholes
▶ Characterization of Soils
▶ Classification of Rocks
▶ Classification of Soils
▶ Cone Penetrometer
▶ Drilling
▶ Drilling Hazards
▶ Engineering Properties
▶ Excavation
▶ Geophysical Methods
▶ Hydraulic Fracturing
▶ Liquid Limit
▶ Piezometer
▶ Plastic Limit
▶ Rock Field Tests
▶ Rock Laboratory Tests
▶ Soil Field Tests
▶ Soil Laboratory Tests
▶ Water
References
Deere DU, Deere DW (1988) The RQD index in practice. In: Proceedings symposium rock classification engineering purposes. ASTM
special technical publications, vol 984. Philadelphia, pp 91–101
Monnet J (2015) In situ tests in geotechnical engineering. Wiley,
New York, p 398
Price DG (2009) In: De Freitas MH (ed) Engineering geology: principles
and practice. Springer, Berlin, p 450. ISBN 3-540-29249-7
Small J (2016) Geomechanics in soil, rock, and environmental engineering. CRC Press, Taylor and Francis Group, Boca Raton, p 541
USDA – United States Department of Agriculture (2012). Chapter 5:
Engineering geology logging, sampling, and testing. Part 631 –
National engineering handbook, p 56
Boreholes
Boreholes
Noureddine Gaaloul1, Saeid Eslamian2 and
Kaveh Ostad-Ali-Askari3
1
Water Resource Management, INRGREF, Ariana, Tunisia
2
Department of Water Engineering, Isfahan University of
Technology, Isfahan, Iran
3
Department of Civil Engineering, Isfahan (Khorasgan)
Branch, Islamic Azad University, Isfahan, Iran
Synonyms
Drill hole; Drilled well
Definition
A narrow hole drilled to establish the nature of, sample, test,
or monitor soil, bedrock or contained fluids and gases or for
abstraction of water or minerals.
Borehole drilling has a long history. By at least the Han
Dynasty (202 BC–220 AD), the Chinese used deep borehole
drilling for mining and other projects. The British sinologist
and historian Michael Loewe (Lowe 1959) states that, at that
time, borehole sites could reach as deep as 600 m (2000 ft) but
it was after the development of petrol and diesel engines that
deep boreholes became generally practicable.
The borehole drilling system consists of a drill head which
powers the operation, a drill string which extends down the
borehole, and a drill bit which cuts through the substrate. The
drill string may be surrounded by a collar separated from the
drill string by an annular space. The annular space allows
water or mud to be pumped down and for soil and cuttings to
be flushed up to the ground surface. The practical limits on the
depth and rapidity with which a borehole can be drilled, and
the diameter of the bore, is governed solely by the size and
power of the rig used. If a borehole is required for use over a
period of time, if it is into uncohesive deposits, or if it is deep,
a lining or casing of plastic, steel, or iron is sunk to protect the
hole from collapse (Arnalich 2011).
The main techniques involved in the construction of boreholes (ICRC 2010) are percussion, rotary, and sonic:
Light cable percussion technique – also known as shelland-auger, this is a relatively quick and cheap method for
drilling to depths up to about 60 m and to recover samples
on the auger. It is used extensively in civil engineering and
shallow mineral deposit site investigations.
Boreholes
Air percussion technique: This technique of percussion
drilling utilizes compressed air to operate a down-hole air
hammer on the end of the drill string that helps break the
rock formation. This borehole drilling mode always
requires the skills of an expert. The compressed air is
usually used to operate an air hammer which is situated
deep down the hole.
The rotary technique: In rotary drilling, a drill bit is attached
to a length of connected drill pipe. The drill bit is made of
strong metals such as tungsten, so that the rotating drill bit
can easily grind the rock. Drill fluids (sometimes referred
to as drilling mud) are circulated through the drill string
into the borehole and back to the surface carrying (flush)
the broken pieces (cuttings) of bedrock upwards and out of
the hole. This fluid also serves as a formation stabilizer
preventing possible caving-in of unstable sand or weak
rock before the well casing or well screen can be installed.
Furthermore, this fluid acts as a drill bit lubricant. As the
drill intersects water bearing rock formations, water will
eventually flow into the hole. Drillers, or hydrogeologists,
on site will carefully monitor the depth of water “strikes”
and keep a note of the formations in which they occur.
Sonic drilling technique – an oscillator in the drill head
generates high-frequency resonant energy which is directed
down the drill string causing soils in a narrow zone between
the string and head to lose structure and reduces friction so
that soil or cuttings can be readily flushed away.
Boreholes require sophisticated technology with the right
appropriate technical design, together with proper knowledge
of the underlying target, such as an aquifer or oil reservoir.
Unfortunately, the importance of good quality borehole design
and construction is often underestimated. The lifetime of a
borehole and the efficiency of its functioning depend directly
on the materials and the technology used. Borehole “failure” is
often linked to incorrect design and construction of the hole.
Constructing, or repairing, boreholes requires specialized
knowledge and technical expertise, much of which can be
gained from the standard literature; but field operations in
remote areas or in difficult conditions often require flexibility
and imagination in avoiding and solving technical problems.
During borehole drilling, certain problems may be encountered (Azar and Robello Samuel 2007). The drill is expected
to act moderately. If pushed down excessively on the rock
surface or rotated too quickly, the drill bit may be destroyed.
On the other hand, if the drilling does not produce enough
force, hard rock layers will not be penetrated. Caution may be
needed if the top of bedrock or a competent layer needs to be
identified (e.g., prior to piling) because drilling into large
boulders might be mistaken for detecting the actual interface.
Also, drilling hazards may be encountered (e.g.,
69
contaminants, polluted water, unexploded ordnance, or natural gases or oil under high pressure). Problems may also arise
if shallow drilling encounters voids such as natural caves or
unrecorded mine cavities.
A variety of “downhole tools” are lowered into boreholes
for testing and monitoring such as geophysical tools to investigate adjacent strata or to secure data to interpolate between
groups of boreholes (Scott Keys, W, Scott Keys 1997) or for
monitoring of ground water strata (e.g., piezometers).
Engineering Site Investigations and Works
Site investigations for construction projects or evaluation of
potentially polluted or contaminated land mainly consist of
relatively shallow drilling and sampling (Clayton et al. 1995;
SISG and ICE 2013). Some holes are drilled and then made
safe very quickly but others are kept open for monitoring of
groundwater or gas emissions. Systematic site investigation
requires boreholes to be drilled on a grid pattern with the initial
spacing between boreholes being determined by the expected
distribution of the ground characteristics that are being examined and new boreholes at different spacings being made if the
need arises to investigate unexpected features. Deeper drilling
is needed to investigate larger scale problems, for instance to
define the slip planes of landslides. Boreholes are also sunk for
dewatering of excavations and draining water from landslides.
Water Abstraction
In boreholes for water supply (Figs. 1, 2 and 3), the bottom
section of the lining has slots to allow water to enter the
borehole. Gravel is placed at the bottom of the lining to
improve flow and provide filtration. The design and construction of boreholes and wells for groundwater extraction is very
technical and requires expert groundwater hydrologists and
engineers. Clark (1988) deals comprehensively with the location and installation of water supply boreholes, whereas the
maintenance, monitoring, and rehabilitation of such systems
are reviewed by Howsam et al. (1995) and Detay (1997).
A less specialized overview is given by Brassington (1995).
Unless in an area with artesian conditions, a pump is required
to bring water from the borehole to the surface.
Mineral Exploration
When holes or wells are drilled for the purpose of evaluating
the content of the hole as retrieved, it is called exploration
drilling (Annels 1991). Mining companies utilize this type of
B
70
Boreholes
Boreholes, Fig. 1 Drilling a
borehole for water
Boreholes, Fig. 2 Drilling a
borehole for water
drilling to retrieve mineral samples of a specific location for
the purpose of evaluating the samples to determine whether
the quality and quantity of a specific mineral are sufficient to
make mining at the location viable. Reverse circulation is one
method used and it entails retrieval of the drill cuttings, using
drill rods that are used for the transport path of the cuttings to
the surface. A hammer drives the tungsten steel drill point into
the rock or soil. With this method, depths of up to 500 m can
be drilled. The retrieved material is dry. Odex and Tricone
systems are used in reverse-circulation drilling.
With Odex, the hammer drill bit fits at the end of the steel
casing and the hammer is used for crushing the material,
which is blown up into the casing where the retrieved cuttings
are transported to the surface. The system is used when there
is a risk of rock collapsing in the drill area. This is a timeconsuming and sometimes very expensive method, but it is
Boreholes
71
Boreholes, Fig. 3 Drilling a
borehole for water
B
often the only type of method that can be used to prevent
rockfalls. The Tricone system is used for water, oil, and
petroleum retrieval. It entails roller cone bits grouped into a
drill bit that rotates into the rock formation.
It is a suitable method when the drill bits must be protected
and when only a small sample of content has to be retrieved.
Core drilling is normally used when faster exploration drilling
is needed. It can also be used in the construction sector for
drilling pipe holes.
Mineral Extraction
A borehole is drilled for extraction of minerals relying on a
process that uses high-pressure water. The water jets make it
possible to drill into hard rock, whether in an open-pit floor,
underground mine space, land surface, or from a vessel in the
sea or on a lake. The first step is to drill to the desired depth
from the surface. The next step is to lower a casing column
into the well with the shoe of the casing situated above the top
boundary of the productive mineral. In the case of oil and gas
extraction, the fluid may initially rise to the surface through
the borehole due to pressure but, as time passes, it becomes
necessary to enhance recovery by fracturing the reservoir
rocks (Blake 1979).
In ore mining by borehole, a third step involves the lowering of the borehole mining tool into the drill well (Pivnyak
et al. 2017). This method requires less capital outlay than
many other mining methods and it makes it possible to work
in otherwise inaccessible areas that are too dangerous for
conventional mining. It has a relatively low environmental
footprint and allows for better mobility when it comes to
changing mining locations. More selectivity can be applied,
meaning less wastage and higher profits. The method is
frequently used for mining minerals such as gold, uranium,
diamonds, coal, and quartz sand. It is also used for oil and gas
extraction. Boreholes can also be used for solution mining,
where water is pumped in, dissolves a mineral such as salt to
form brine which is then recovered at the surface.
Arrays of boreholes are drilled on a linear or grid pattern
for the purpose of inserting charges for blasting to break up
the mineral (Gokhale 2010) (Fig. 4).
Directional Drilling
Directional drilling is the drilling of oblique or horizontal
boreholes (Azar and Robello Samuel 2007). It is used for a
variety of purposes. For instance:
• In deep drilling for oil or natural gas, a borehole is made at
a single suitable location and is then used for drilling of a
number of oblique borings to further investigate and
exploit a reservoir, which minimizes the number of wellheads that affect the surface environment
• To reduce the pressure of a well, in order to minimize the
risk of a pressure blow-out
72
Boreholes
Boreholes, Fig. 4 Grid pattern
of boreholes (top left) drilled for
blasting at a mineral working
(Photograph by Dr. BR Marker)
• For hydraulic fracturing of oil shales to release the hydrocarbons or to exploit coal-bed methane
• Horizontal drilling for installation of utilities
Costs
The costs of boreholes depends on the depth of drilling, the
diameter of the hole, and the need for casing, but it is also
influenced significantly by the applied design as well as the
difficulty to construct a borehole in certain geological formations (Stapenhurst 2009). It is fairly common for developers
to try to reduce costs by not allowing for the insertion of
casing or by reducing the number of boreholes that is needed
to adequately investigate the problem. In the short term, these
seem costly but almost always pay off in the long run. Thus
casing will allow for the borehole to stay open for years after
completion, and if correctly installed, it will also assist in
keeping the borehole clean and free of material that could
damage a borehole pump. Also, an adequate number of boreholes in a construction site will normally avoid unexpected
later costs for remedial works and delays to development. It is
important to have professionally competent specialists when
designing, undertaking, and using boreholes.
purposes, and monitoring of groundwater behavior and
composition.
Cross-References
▶ Aquifer
▶ Artesian
▶ Borehole Investigations
▶ Designing Site Investigations
▶ Dewatering
▶ Drilling
▶ Drilling Hazards
▶ Geophysical Methods
▶ Groundwater
▶ Hydraulic Fracturing
▶ Mining
▶ Piezometer
▶ Water
▶ Water Testing
▶ Wells
References
Summary
Boreholes are made for a variety of purposes including
the investigation and sampling of the geological succession for construction, water abstraction, or mineral extraction
Annels AE (1991) Mineral deposit evaluation: a practical approach.
Springer, Heidelberg
Arnalich S (2011) Equipping a borehole Arnalich water and habitats.
Arnalich, Almeira
Azar JJ, Robello Samuel G (2007) Drilling engineering. Penwell Books,
Houston
Boulders
Blake R (1979) A primer of oil well drilling, 4th edn. Petroleum Extension Service, Austin
Brassington R (1995) Finding water: a guide to the construction and
maintenance of private water supplies. John Wiley and Sons,
Winchester
Clark L (1988) The field guide to water wells and boreholes. John Wiley
and Sons, Winchester
Clayton CR, Matthews MC, Simms N (1995) Site investigation:
a handbook for engineers, 2nd edn. Wiley-Blackwell, Hoboken
Detay M (1997) Water wells: implementation, Maintenance and Restoration. John Wiley and Sons, Chichester
Gokhale BV (2010) Rotary drilling blasting in large surface mines.
CRC Press, Abingdon
Howsam P, Misstear B, Jones C (1995) Monitoring, maintenance and
rehabilitation of water supply boreholes, Report 137. Construction
Industry Research and Information Association, London
International Committee of the Red Cross (ICRC) (2010) Technical
manual: borehole drilling an rehabilitation under field conditions.
Ref 0998-e books. ICRC, Geneva
Lowe M (1959) Some Han-time documents from Chü-yen. T'oung Pao
47:294–322. JSTOR 4528102
Pivnyak G, Bondarenko V, Kovalevs'ka IC, Illiashov M (2017) Mining
of mineral deposits. CRC Press, Abingdon
Scott Keys W (1997) A practical guide to borehole geophysics in
environmental investigations. CRC Press, Boca Raton
Site Investigation Steering Group (SISG), Institute of Civil Engineers
(ICE) (2013) Effective site investigation, 2nd edn. ICE Publishing,
London
Stapenhurst T (2009) The benchmarking book. Butterworth-Heinemann,
Oxford, pp 341–365
Boulders
Peter T. Bobrowsky
Geological Survey of Canada, Sidney, BC, Canada
Definition
Rock fragments, particles, or grains larger than 200 mm
in size (British soil scale) or greater than 256 mm in size
(North American scale). Boulders are the largest grain size
within the category of gravel. The term likely derives from
the Swedish term “bullersten” or Middle English term
“bulderston.”
73
features. Large glacial erratics are static features generally
avoided during construction efforts and more often a tourist
attraction (e.g., Okotoks erratic in Alberta, Canada). Typical
natural processes capable of transporting boulders include landslides (e.g., debris flows, rock avalanches), lahars, tsunamis,
flash floods (including natural and artificial dam bursts), and
storms (typhoons, super storms, etc.) (Dewey and Ryan 2017;
Hungr et al. 2014). Artificial efforts to move boulder sized rocks
require mechanized support (e.g., backhoe).
Resedimentation of boulders is a significant issue and
poses risk to humans and infrastructure around the world.
In mountainous areas, debris flows are capable of moving
large numbers of boulders at fast speeds along natural and
engineered channels that are crossed by roads and bridges.
The damage to bridge piers and other support structures is
substantial and solutions require engineered design needs
such as the construction of anti-collision pier structures on
the upstream side of bridge piers to reduce potential damage
from forces associated with boulder impacts. Comparable
considerations are required for dams, weirs and other structures affected by boulder impact and deposition.
In the assessment of boulder movements, the calculated
Froude number (a ratio of inertial and gravitational forces)
can range appreciably depending on the local conditions:
natural versus hard-engineered channels, noncohesive versus
bedrock surfaces, bulk density of the fluids, boulder composition and porosity, impulsive forces, etc. Challenges for
engineering geologists includes appropriate modelling applications to advise the civil engineers.
Cross-References
▶ Bedrock
▶ Bridges
▶ Drilling Hazards
▶ Fluvial Environments
▶ Glacier Environments
▶ Hazard
▶ Landslide
▶ Mountain Environments
▶ Sediments
▶ Tsunamis
Context
References
Boulders range in size from a minimum of 200 or 256 mm to
isolated pieces weighing multiple tons (megaboulders or megaclasts). Glacial deposits around the northern hemisphere commonly host boulder sized clasts in the form of isolated erratics or
within chaotic multitextural deposits such as ice-contact gravel
Dewey JF, Ryan PD (2017) Storm, rogue wave, or tsunami origin for
megaclast deposits in western Ireland and North Island,
New Zealand? Proc Natl Acad Sci 114:E10639–E10647
Hungr O, Leroueil S, Picarelli L (2014) The Varnes classification of
landslide types, an update. Landslides 11:167–194
B
74
Bridges
Vasant Matsagar1, Saeid Eslamian2, Kaveh OstadAli-Askari3, Mohammad Raeisi5, George Lee6, Sona Pazdar7
and Aida Bagheri-Basmenji4
1
Department of Civil Engineering, Indian Institute of
Technology (IIT) Delhi, New Delhi, India
2
Department of Water Engineering, Isfahan University of
Technology, Isfahan, Iran
3
Department of Civil Engineering, Isfahan (Khorasgan)
Branch, Islamic Azad University, Isfahan, Iran
4
Department of Water Resources Engineering,
Tabriz University, Tabriz, Iran
5
Department of Civil Engineering, Khomeinishahr Branch,
Islamic Azad University, Khomeinishahr/Isfahan, Iran
6
Institute of Bridge Engineering, University at Buffalo,
New York, NY, USA
7
Civil Engineering Department, Aghigh University,
Shahinshahr/Isfahan, Iran
Synonyms
Bridges
bridges serve to cross roads without mixing of the traffic
moving across in different directions. Therefore, they are an
essential part of daily life that aids a prospering trade and
commerce in a city. Maintenance and repair of bridges, therefore, has consequences for the economy of the region, which
mandates finding technological solutions for increasing their
longevity.
Bridges are called life-line structures because apart from
the day-to-day services, during natural calamities such as
earthquakes or floods, they facilitate in providing emergency
relief by enabling supply of food, medicine, etc., into hazard
affected areas. Typically, structural redundancy in bridges is
relatively low, which makes them vulnerable to earthquakes
and strong winds. The relief and rehabilitation work may
therefore be adversely affected if bridges receive severe damage or experience catastrophic failures during natural hazards.
Moreover, bridge failure adversely affects commerce and
services, incurring hefty repair costs, and of utmost importance, may cause loss of human lives.
Bridge Components, Planning, Analysis, and
Design
Trestle
There are five main components that make up a typical bridge.
They include:
Definition
• Pile – A concrete post that is driven into the ground to act
as a leg or support for the bridge. It is driven into the
ground using a pile-driver.
• Cap – The cap sits on top of a group of piles and disperses
pressure to the piles below.
• Bent – This is the combination of the cap and the pile.
Together, with other bents, act as supports for the entire
bridge.
• Girders – Girders are like the arms of the bridge. They
extend from bent to bent and support the bridge decking.
They also help disperse pressure to the bents.
• Decking – The decking is the road surface of the bridge.
It rests on the girders, supported by the bents that are made
of caps and piles.
A raised structure that allows the movement of vehicles or
pedestrians over an obstacle.
Introduction
For millennia bridges have been used to cross barriers, typically a river, stream, or valley, by using locally available
materials, such as stones, and timber. Originally, cut trees
were simply placed across streams to allow crossing. Later,
pieces of wood were lashed together to make improvements
in functionality of the bridges. Such bridges are known as
frame bridges. Since these early times bridge engineering has
evolved into a major discipline in itself; one that benefits from
the advances made in other engineering disciplines, such as
engineering geology, water resources engineering, geotechnical engineering, and structural engineering. Based on these
disciplines, modern bridge engineering mainly deals with
(a) planning, (b) analysis, (c) design, (d) construction,
(e) maintenance, and (f) rehabilitation.
In modern society, bridges facilitate surface transportation
for roads and railways and carry facilities such as water/sewer
supply pipelines or electric/telephone communication lines
across streams or gorges. In congested city centers, flyovers/
Bridges are categorized based on their functionality, the
type of materials used, type of bridge construction,
etc. Flyovers, highway bridges, and railway bridges are
some of the major categories of bridges depending upon
functionality. Sometimes bridges are built with more
than one deck (multiple levels) such that; in a double deck
bridge, one deck carries road traffic, whereas the other deck
may carry train traffic. The rest of the details provided herein
pertain mostly to the highway bridges, but are applicable to
other types of bridges with some distinctions. Individual or
mixed (combined) materials are used in bridge construction,
Bridges
75
Bridges, Fig. 1 ATypical Bridge
Structure and Component
Bridge
Expansion
Lane
Median
Lane
Plying
B
Bridge
Abutment
Abutment
Rock
such as steel, concrete, timber. Steel bridges are typically built
for faster speed of construction and railway bridges are
largely constructed from built-up steel sections. However,
steel bridges suffer from corrosion-related degradation,
heavier weight, and special detailing requirements to accommodate thermal expansion and contraction. Historically, following the introduction of cement to the construction
industry, reinforced concrete (RC) bridges were commonly
built. However, today most bridges consist of prestressed
concrete (PSC). Furthermore, precast concrete or prefabricated elements are used in bridge construction; however,
they are less common. Concrete bridges also suffer from
shrinkage and long-term creep-related effects. Hence, newer
materials for bridge construction are now being developed.
Typically, a bridge structure consists of a deck supported
on bearings, as shown in Fig. 1. The bridge bearings facilitate
accommodating temperature-dependent expansion and contraction movements experienced by the deck, and now they
are designed to protect the bridge from earthquake-induced
lateral forces. The bridge bearings are supported over abutments or pier-caps and effectively transfer the vertical loads
from the deck to the abutments or piers. The different types of
bearings commonly used in bridges are: laminated/ neoprene
bearings, elastomeric (rubber) bearings, sliding bearings, potPTFE bearings (Polytetrafluoroethylene), rocker/roller bearings, knuckle bearings, spherical bearings, etc. In addition,
when the length of the bridge is long, expansion joints accommodate expansion and contraction in the longitudinal direction (Fig. 1).
The abutments retain Earth on both sides of the stream at
the bridge site, whereas they also serve as end supports to the
bridge. Sometimes, the abutments are supplemented with
wing walls to retain loose soil on either end of the abutments
and additionally provide guided protection from erosion
resulting from high velocity water flowing in the stream.
Behind the abutments, bridge approaches are constructed
mostly from earthwork and retaining/RE walls. Hence, the
abutments are generally designed as Earth retaining structures
of masonry or concrete. Under the action of vertical and
Rock
lateral loads, such an Earth retaining structure, an abutment
is designed as a member that will not develop tensile stress, if
steel reinforcement is not to be used. This is ensured by
calculating resultant stresses acting within the critical section
of the abutment as:
s¼
P M
y
A I
(1)
where s is the resultant stress; P is the normal/ direct load on
the critical section; A is the area of the critical section in the
abutment; M is the bending moment on the section; I is the
moment of inertia of the section; and y is the extreme fiber
distance.
The piers provide intermediate support to the bridge,
which essentially function as columns, that is, predominantly
axially loaded members with some bending moments.
The bending moments are due to eccentricity of the vertical
loads, direct transverse loads applied from earthquakeinduced forces or strong winds, lateral earth pressure applied
at the abutment may be transmitted through the deck to the
piers, thermal movements of the deck induce lateral forces on
the piers, and braking force applied by the moving vehicles
also induces longitudinal forces on the deck, which may in
turn impose bending moments on the piers. For an axially
loaded compression member, like a bridge pier, the critical
buckling load-carrying capacity (Pcr) can be estimated using
linear stability theory proposed by Euler:
Pcr ¼
p2 EI
L2
(2)
where E is the modulus of elasticity; I is the moment of inertia
about axis of buckling or second moment of area; and L is
the effective length of the compression member, pier. In the
presence of the bending moment, in order to calculate the
flexural stresses induced in the pier, the classical bending
formula can be used:
76
Bridges
s M E
¼ ¼
y
I
R
(3)
where s is the bending stress; y is the extreme fiber distance in
the cross-section from the neutral axis; M is the bending
moment acting on the pier; and R is the radius of curvature
of the flexural member, pier. Using Eq. 3, it is possible to
calculate maximum compressive or tensile stresses induced in
the pier under the action of axial load and applied bending
moments. These stresses are subsequently used in the design
of the pier.
The bearings divide the bridge vertically in two parts:
(a) superstructure above the bearings and (b) substructure
below the bearings. Thus, the bridge deck is part of the
superstructure, whereas the pier-cap and piers are the parts
of the substructure. The bridge deck supports several structural and nonstructural components such as overlays, plying
surface, handrails, footpath, curbs, which all form part of the
superstructure. Sometimes the substructure also includes
returns and wing walls, which are required along with the
abutments to support the Earth laterally and prevent erosion
of soil on the banks. These two parts of the bridge, superstructure and substructure, are supported over the third part,
the foundation.
Depending upon the site conditions, construction feasibility, type of loading applied, and other factors, the type
of foundation is determined. Some common types of bridge
foundations includes open/isolated footing, spread foundation, well foundation, raft foundation, and pile/pile-group
foundation. Figure 2 shows a general arrangement of a typical
three-span continuous bridge supported on pile-group foundation. Note that the geology of the bridge site plays an
important role in the choice of the foundation. Geological
knowledge of the site under consideration for the bridge is
useful in the planning, analysis, design, and construction
phases. Decisions on the type of bridge to be selected, its
foundation type, consideration of the geological features in
assessment of the structural behavior of bridges, and construction technology to be adopted are made based on the
engineering geology. A reconnaissance survey is conducted
during planning stage of the bridge to select such a site along
the stream that possibly has well-defined banks, approaches to
the bridge on either side are fairly straight, and the foundation
strata is firm - preferably hard rock. Boreholes are taken
at specific intervals around the bridge site to specific depths
to study the bore-logs for assessment of the geological features and thereby deciding the type of foundation to be
adopted.
Several types of preliminary surveys are conducted when
deciding the site and bridge type, such as traffic survey,
topographic survey, geological survey, geotechnical survey,
hydrological survey, meteorological survey, which sometimes together is termed as bridge survey. Once the requirements of a bridge on a particular route in terms of volume and
characteristics of the traffic are determined from the traffic
survey, a topographic survey of the area is conducted to give
an idea about the locality or surrounding area about peaks,
valleys, obstructions, and elevations. Based on that, a site for
bridge construction is decided by subsequently conducting
other surveys, including cost-benefit/bridge economics studies and environmental impact assessment, which all form part
of the technical feasibility report for the bridge.
For the selected bridge location, a geological survey is
subsequently conducted for surface and subsurface investigations to prepare topographic maps, contour maps, and geologic maps, which essentially dictate the foundation design
Deck
Pier Cap
Abutment
Pier
River Bed
Pile Cap
Pile
Bed Rock
Bridges, Fig. 2 A Three-span continuous bridge supported on pile-group foundation
Bridges
for the bridge. To avoid any possible support settlement,
unyielding founding strata are necessary, which is established
based on the boreholes taken in a specific array on the site that
provide data about the lithological variation, faults, and rock
formations. The borehole locations are selected along the
proposed center-line of the bridge with some spacing, which
is decided based on variations in the geological features
within the stretch. If the geological features are varying substantially, a dense grid of boreholes is warranted. Especially,
in case of the long-span bridges where it is anticipated that the
geologic environments at the ends and intermediate supports
may vary considerably.
The bore-logs extracted from the boreholes are arranged
systematically, and borehole data are carefully studied to
the desired depths or typically until hard rock is reached.
Moreover, a ground water table assessment is made from
the geological explorations. At some sites, an aquifer may
exist that needs to be accounted for along with the subsurface
water, if any, while taking decisions related to the foundation
design. Such studies called hydrogeological studies are
conducted based on the need at a particular site. Past geological records and reports are also studied to understand variations in the subsurface characteristics through time including
reporting of former earthquakes or strong wind-storm events.
The seismic data of the site are a key input in the structural
design of bridges. For long-span bridges, in particular, the
attenuation of the seismic waves along their path of propagation depends upon the geological characteristics, which is also
an input for evaluating dynamic response of the long-span
bridges under multisupport earthquake excitations. It is essential to reach firm and stable rock in the case of the major
bridges; therefore, if necessary geophysical surveys are
conducted, such information is used by geotechnical engineers to determine the liquefaction potential at the bridge site.
A geological team conducts detailed geological investigation,
prepares maps of the local geological features, conducts tests
on the sampled geological materials in the field and laboratory, synthesizes and interprets the results, and provides a
report to the geotechnical engineer, hydrological engineer,
architect, and structural engineer or bridge designer.
For the selected bridge site, based on the local geological
investigation, further planning and design of the bridge proceed with hydrological assessment and functional planning.
Hydrological data are gathered for the bridge site to determine
the water flow characteristics such as discharge, velocity,
yearly flood levels, characteristics of rainfall in the catchment
area over a typical return period of 120 years. These inputs are
used to calculate the design discharge and subsequently to
design the free waterway, which is the passage provided
underneath the bridges for water to flow from an upstream
to downstream direction. The mean velocity (V in m/s unit) of
the water current in a stream is calculated using Chezy’s
formula:
77
pffiffiffiffiffiffiffiffi
V ¼C R s
(4)
where R is the hydraulic radius (in m unit); s is sine of the
slope (in m/m unit); and C is a constant determined from the
Kutter’s formula:
0:00155 1
þ
23 þ
n
s
C¼
n
0:00155
1 þ pffiffiffi 23 þ
s
R
(5)
where n is the surface roughness coefficient.
Due to the construction of the bridge piers, the naturally
available linear waterway is reduced to an effective waterway
at the bridge site. Thereby, the velocity of water increases in
the stream because of the reduced waterway. Such higher
velocity of water mandates introducing several design features in the bridge. For example, cutwater and ease-water are
provided, respectively, at the upstream and downstream faces
of the piers in order to streamline the flow of the water, as
much as possible. The projecting shapes of the cutwater and
ease-water are designed such that the pier remains unaffected
from the striking water or floating bodies. Furthermore, freeboard, afflux, and scour depth are determined based on the
hydrological investigation, except in the case of a high bridge
where water level is not a concern. The freeboard provided
in bridges maintains minimum level difference between the
anticipated highest flood level (HFL) in the stream and the
formation level of the bridge, i.e., bottom most part of
the bridge deck. Note that the HFL is added with afflux,
which is the increase in the water level upstream of the bridge
site, due to obstruction in the waterway caused on account of
the bridge piers. Generally, such vertical clearance above the
water level or freeboard is maintained minimally at about
0.5 m. The flow of water contributes to riverbed erosion,
called scouring action. While designing the foundation, protection works, and bunds for the bridges, scour depth must be
determined. The velocity of the water current varies along the
flow, which necessitates estimating conservative scour depth
by adopting sounding procedures at different locations in the
direct vicinity of the bridge site.
Upon completion of the bridge surveys, and consideration
of the inputs received, geometric design of the bridge is
undertaken. The width of the highway bridge design is
based on the traffic studies conducted on the path and functionalities to be served by the bridge. The width of the bridge
accommodates the actual carriage way depending upon the
number of traffic lanes, median(s), footpath(s), bicycles path,
service lines carried across, etc. In the process of this design,
future projections on the traffic requirements are also made.
Generally, a service life of 120 years is considered sufficient
for a bridge.
B
78
Bridges
The planning stage of the bridge further includes decisions
on how many piers must be provided, that is, how many spans
the bridge requires. If the number of piers provided is
increased, the spans of the bridge are reduced; this increases
the cost of constructing piers and foundation, and the cost of
constructing the bridge deck reduces. On the other hand, if the
number of piers provided is reduced, the required spans for the
bridge increase; this increases the cost of constructing the
bridge deck, and the cost of constructing the piers and foundation reduces. Thus, because the two requirements contradict
each other, in order to achieve economy in bridge construction,
an economical bridge span is calculated such that the cost of
bridge construction is minimized. In other words, if the costs of
construction for the superstructure and substructure are fairly
equal, economy in bridge construction is achieved.
The alignments of the bridge in the vertical plane and horizontal planes (footprint) are major planned architectural features.
Generally, long-span bridges in deep streams are provided with
high vertical curve, such that underneath the intermediate span
(s) ship movement can be facilitated. The vertical profile and
length of the bridge, including approaches on either side, are
determined based on the ruling gradient, which is the maximum
allowed slope for the plying-surface. The horizontal alignment
of the bridge is governed by the geological features and traffic
requirements. Note that depending upon the use of the bridge as
highway or railway, the vertical and horizontal alignments and
slopes are required to be carefully designed.
The bridges that are curved in plan are provided with
super-elevation, that is, banking of the plying-surface. Due
to the centrifugal forces experienced by moving vehicles
away from the center of the curvature, they have a tendency
to be pushed in the outward direction from the bridge. In order
to avoid this, the outer edge of the bridge is constructed at a
higher elevation relative to the inner edge of the bridge, called
super-elevation. The super-elevation provided for a bridge
mainly depends upon the design vehicle speed and radius of
curvature of the bridge in plan. If e denotes the rate of superelevation in percent, f is the lateral friction factor (typically
assumed as 0.15), V0 is the velocity of the design vehicle in
m/s unit, R is the radius of circular curve in m unit, and
g denotes acceleration due to gravity (9.81 m/s2) then:
2
e¼
V0
gR
f
(5)
Based on the locality of the bridge site, availability of
the construction material, equipment, labor, and similar factors, choice on the type of bridge is made for the site under
consideration. Also, the choice of the bridge material depends
upon service life and intended use of the bridge. Today,
architects are employed to ensure aesthetics of the bridge is
appealing to the landscape and that it offers attractive features
of engineering marvel.
Upon completing architectural planning, geotechnical and
structural design activities begin. The foundation type of the
bridge is governed by the geological features at the site,
anticipated loads to be transferred from the bridge, and the
economical bridge span. The geological and geotechnical
features include type of founding strata, soil condition,
water table, and scour depth. Moreover, feasibility of
constructing a particular type of foundation, whether shallow
or deep, at the site is governed by several factors, though
approach to the foundation site remains one of the most
crucial factor in the decision-making. If caissons/ cofferdams
are required to be constructed for facilitating building the
foundation, the cost of foundation construction increases.
In shallow depth water, a watertight box or casing, called
caisson, is used for facilitating the construction work.
A cofferdam is used for deep water depths, to create watertight working space around the foundation by preventing
inflow of water at the construction site from the stream. For
relatively large bridges, well foundation is a suitable choice to
transfer the high vertical and horizontal loads effectively
to the hard bedrock. However, it requires a costly sinking
operation of the heavy well foundation in the stream. On the
other hand, if the bedrock is available at relatively greater
depths, then pile or pile-group foundation can be chosen.
The piles typically transfer the loads through skin friction
and end reaction. The type of piles to used, such as cast-in
situ, driven, drilled/bored piles, etc., and the number of piles
to be provided underneath the piers depends upon the loads to
be transferred as well as the geological and geotechnical
features of the bridge site.
The class of design load used for a bridge depends upon
the manner in which it is anticipated to experience the loads
in its useful service life. Generally, design life of the bridge is
considered to be 120 years. Codes of practice in different
countries provide guidelines on the load class of the bridge.
For highway bridges, impact factor is used as a multiplying
coefficient to the moving live loads in order to account for
additional forces induced on the bridge. Moreover, due to
sudden braking and acceleration of the vehicles plying on
the deck, additional forces used in the design are called
braking loads. Some of the major loading considerations in
the bridge design include vehicle overloads, vehicle collision/impact, earthquakes, strong winds, flood, accidental
fire, temperature, blast, fatigue, etc. Some geotechnical engineering concerns in this context pertain to uneven soil settlement, foundation failure, slope instability, excessive
scouring, etc.
In the past, graphical approaches and influence line diagrams were favored tools of bridge designers for structural
analysis. Later, matrix-based methods became more popular
for analysis of bridges to determine design forces under
several types of loads and their combinations. One of the
well-recognized methods of analyzing bridge deck has been
Bridges
grillage analogy, which is still in use in the bridge design
practice. However, today finite element (FE) techniques have
replaced most of the classical bridge analysis methods. The
state-of-the-art FE packages not only facilitate working conveniently with several load types and their combinations but
are also able to model advanced engineered materials introduced in the construction sector of-late. Further, with the
development of high-strength materials and modern
construction techniques, the components of bridges have
become more slender, which therefore typically necessitates
conducting nonlinear buckling/stability analysis. Such stability analysis incorporates geometric and material nonlinearities and is facilitated by the advanced FE software.
The design procedures of steel, RC, and PSC bridges
were based on working stress method (WSM) formerly,
which is also called allowable stress design (ASD). In the
WSM or ASD, the loads acting on the bridge structures and
strengths of the materials used are deterministic. Hence, a
defined factor of safety was in practice then and used to be
around 2. The safety factor was defined as the ratio of the
strength or capacity of the structural member to the loads or
actions imposed. However, quite rationally, the WSM or
ASD approach is now replaced by the limit state method
(LSM), which is also called load and resistance factor design
(LRFD). In the LSM or LRFD, the loads acting on the bridge
structures and strengths of the materials used are
probabilistic. Hence, actual loads acting on the structural
member and resistance offered by the material of the member are taken in to account, which provides a realistic and
reliable factor of safety with a defined confidence level. Most
of the international standards now follow the LSM or LRFD
approach for the design of bridges.
Types of Bridges
Several types of bridges are planned, designed, and
constructed in real-life applications depending on needs of
the site/location. Apart from the routinely constructed stationary or immovable bridges, under certain circumstances movable bridges are required to serve specific intended purposes.
Movable bridge is that category of bridges which can be
moved horizontally or vertically from/on their spans or
rotated in horizontal or vertical planes, as per the required
arrangement. The following are some types of bridges,
explained with their functioning.
1. Arch bridge: has a curved geometry and transfers the
dead and live loads to the supports obliquely. They may
be either be (a) two-hinged arch, with hinges provided
only at the piers and abutments, or (b) three-hinged arch,
with one hinge provided at the crown of the arch distinct
from the hinges at the piers and abutments.
79
2. Bascule bridge: is used where the bridge span is required
to be opened to allow ship traffic underneath, by rotating
the bridge span in a vertical plane.
3. Bowstring bridge: consists of a curved bow or rib, which
at both ends is connected with a taut horizontal tension
chord or rod.
4. Cable-stayed bridge: stay-cables are used to support the
deck, whereas the loads are transferred by the stay-cables
through a connected pylon. Generally, a vertical columnlike member pylon is made an architectural feature.
5. Cantilever bridge or balanced cantilever bridge: the spans
cantilever from the pier and often the large cantilever
moments are balanced by counteracting moments offered
by constructing a cantilevered bridge span in the opposite
direction on the same pier.
6. Culvert: are typically short-span box or pipe type concrete bridges used to cross narrow and shallow streams.
7. Draw bridge, revolving draw bridge, rolling draw bridge,
or pullback bridge: can be taken from their position,
turned aside in a horizontal plane, withdrawn, or retreated
longitudinally back to allow ship traffic through a stream.
8. Folding bridge, or jack-knife bridge: can be folded (like
collapsing doors) and opened whenever so required.
9. Foot bridge or pedestrian bridge: is exclusively built to
serve only pedestrian traffic.
10. Highway bridge or wagon bridge: is built to serve highway traffic.
11. Lattice bridge: such steel bridges have riveted or bolted
trusses containing several diagonally placed inclined
members.
12. Leaf bridge: leaf or leaves are swayed on hinges to make
an opening whenever so required.
13. Lever-draw or motor bridge: are moved by using lever
system or motors.
14. Lift/vertical lift bridge, or hoist bridge: can be lifted
upwards in a vertical plane on two supporting columns
so that movement of ship traffic from underneath is
possible.
15. Plate/girder bridge: is made of steel plate girders or
lattice.
16. Pontoon bridge, boat bridge, floating bridge, or bateau
bridge: float on water by means of pontoons, barges, or
boats.
17. Railway bridge: is exclusively built to serve only railway
traffic.
18. Skew bridge: the longitudinal axis of the deck meets the
abutments obliquely in a horizontal plane.
19. Suspension bridge, stiffened suspension bridge, chain
bridge, wire bridge, rope bridge, or hanging bridge: in
these types of bridges, the deck is supported by suspenders made of chains, wires, strings, which are hung
from cables running over two towers on either side and
transfer the loads to the ground at abutment obliquely.
B
80
20.
21.
22.
23.
Bridges
Bridge type definition depends upon the kind of cable
employed. Sometimes, stiffening trusses or wires are
used in these bridges.
Swing bridge, turning bridge, or swivel bridge: the span
is able to rotate in a horizontal plane about a vertical axis
to allow ship traffic.
Trestle bridge: metallic or wooden members form a
portal-type structure above which the deck is supported.
Truss bridge, through-type, or deck-type: the deck is
supported by two parallel trusses placed on the edges in
a longitudinal direction. Depending upon location of the
supported deck, either at the bottom of the truss or above
the truss, they are categorized, respectively, as throughtype or deck-type truss bridges.
Tubular/arch bridge: enclosed space is created for the
users, either using large arcs of tubes or by plate girders
forming a box-type of hollow conduit for passage.
trusses. Arch bridges are either simple or continuous (hinged).
A cantilever bridge may also include a suspended span.
Examples of the three common travel surface configurations are illustrated in the Truss type drawings (Fig. 4). In
a Deck configuration, traffic travels on top of the main structure; in a Pony configuration, traffic travels between parallel
superstructures that are not cross-braced at the top; in
a through configuration, traffic travels through the superstructure (usually a truss) which is cross-braced above and below
the traffic.
Beam and Girder Types
Simple deck beam bridges are usually made of metal or
reinforced concrete (Fig. 5). Other beam and girder types
are constructed of metal. The end section of the two deck
configuration shows the cross-bracing commonly used
between beams. The pony end section shows knee braces
that prevent deflection where the girders and deck meet.
The following four main components describe a bridge. By
combining these items one may give a general description of
most bridge types.
• Span (simple, continuous, cantilever)
• Material (stone, concrete, metal, etc.)
• Placement of the travel surface in relation to the structure
(deck, pony, through)
• Form (beam, arch, truss, etc.)
The three basic types of spans are shown here (Fig. 3). Any
of these spans may be constructed using beams, girders, or
DECK TRUSS
PONY TRUSS
THROUGH TRUSS
Bridges, Fig. 4 Types of bridge travel Truss surface configurations
SIMPLE SPANS
CONTINUOUS SPANS
DECK BEAM
CANTILEVER SPANS
DECK PLATE GIRDER
CANTILEVER SPANS (with suspended span)
PONY PLATE GIRDER
Bridges, Fig. 3 Types of bridge spans
Bridges, Fig. 5 Types of bridge beam and girders
Bridges
81
One method of increasing a girder’s load capacity while
minimizing its web depth is to add haunches at the supported
ends. Usually the center section is a standard shape with
parallel flanges; curved or angled flange ends are riveted or
bolted using splice plates. Because of the restrictions incurred
in transporting large beams to the construction site, shorter,
more manageable lengths are often joined on-site using splice
plates (Fig. 6).
Many modern bridges use new designs developed using
computer stress analysis. The rigid frame type has superstructure and substructure that are integrated. Commonly, the legs
or the intersection of a leg with the deck form a single piece
which is riveted to other sections (Fig. 7).
Orthotropic beams are modular shapes that resist stress in
multiple directions simultaneously. They vary in crosssection and may be open or closed shapes (Fig. 8).
Arch Types
There are several ways to classify arch bridges (Fig. 9). The
placement of the deck in relation to the superstructure
provides the descriptive terms used in all bridges: deck,
pony, and through.
HAUNCHED GIRDER (with splice plates)
However, the type of connections used at the supports and
the midpoint of the arch may be used – counting the number
of hinges which allow the structure to respond to varying
stresses and loads. A through arch is illustrated, but this
applies to all type of arch bridges.
Another method of classification focuses on the configuration of the arch. Examples of solid-ribbed, brace-ribbed
(trussed arch), and spandrel-braced arches are shown
(Figs. 10 and 11). A solid-ribbed arch is commonly constructed
using curved girder sections. A brace-ribbed arch has a curved
through truss rising above the deck. A spandrel-braced arch or
open spandrel deck arch carries the deck on top of the arch.
Some metal bridges which appear to be open spandrel deck
arch are, in fact, cantilever; these rely on diagonal bracing.
A true arch bridge relies on vertical members to transmit the
load which is carried by the arch.
The tied arch (bowstring) type is mainly used for suspension
bridges; the arch may be trussed or solid. The trusses that
comprise the arch will vary in configuration, but commonly
use Pratt or Warren webbing. Although a typical arch bridge
passes its load to bearings at its abutment, a tied arch resists
spreading (drift) at its bearings by using the deck as a tie piece
(Fig. 12).
FIXED (HINGELESS) ARCH
Bridges, Fig. 6 Example of a haunched girder with splice plates
ONE-HINGED ARCH
RIGID FRAME (INCLINED LEG)
TWO-HINGED ARCH
RIGID FRAME (V- LEG)
THREE-HINGED ARCH
Bridges, Fig. 7 Bridge leg configuration
ORTHOTROPIC BEAM
Bridges, Fig. 8 Orthotropic bridge beam
Bridges, Fig. 9 Hinge arch types for bridge classification
SOLID RIBBED ARCH (TIED ARCH)
Bridges, Fig. 10 Solid ribbed arch configuration
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82
Bridges, Fig. 11 Spandrel braced and trussed deck arch configuration
Bridges
Bridges, Fig. 14 King and Queen post trusses
Bridges, Fig. 15 Multiple Kingpost truss and Howe truss
Bridges, Fig. 12 Trussed through arch (tied and untied)
adds a horizontal top chord to achieve a longer span, but the
center panel tends to be less rigid due to its lack of diagonal
bracing (Fig. 14).
Bridges, Fig. 13 Closed and open spandrel deck arch
Masonry bridges, constructed in stone and concrete, may
have open or closed spandrels (Fig. 13). A closed spandrel is
often filled with rubble and faced with dressed stone or
concrete. Occasionally, reinforced concrete is used in building pony arch types.
Truss- Simple Types
A truss is a structure constructed of many smaller parts. Once
constructed of wooden timbers, and later including iron tension members, most truss bridges are now built of metal.
Types of truss bridges are also identified by the terms deck,
pony, and through which describe the placement of the travel
surface in relation to the superstructure (see drawings above).
The king post truss is the simplest type; the queen posttruss
Covered Bridge Types (Truss)
Covered bridges are typically wooden truss structures. The
enclosing roof protected the timbers from weathering and
extended the life of the bridge. One of the more common
methods used for achieving longer spans was the multiple
kingpost truss. A simple, wooden, kingpost truss forms the
center and panels are added symmetrically. With the use of
iron in bridge construction, the Howe truss – in its simplest
form – is a type of multiple kingpost truss (Fig. 15).
Stephen H. Long (1784–1864) was one of the US Army
Topographical Engineers sent to explore and map the United
States as it expanded westward. While working for the Baltimore and Ohio Railroad, he developed the X truss in 1830
with further improvements patented in 1835 and 1837
(Fig. 16). The wooden truss is also known as the Long truss,
and he is cited as the first American to use mathematical
calculations in truss design.
Theodore Burr built a bridge spanning the Hudson River at
Waterford, NY, in 1804. By adding an arch segment to a
multiple kingpost truss, the Burr arch truss was able to attain
longer spans. His truss design, patented in 1817, is not a true
arch as it relies on the interaction of the arch segments with
the truss members to carry the load. There are many examples
of this type in the Pittsburgh area, and they continue to be one
Bridges
83
B
Bridges, Fig. 16 Long “X” truss
Bridges, Fig. 19 Covered Haupt Truss
Bridges, Fig. 17 Covered Burr arch truss
Bridges, Fig. 20 Covered Smith truss
Bridges, Fig. 18 Covered Town lattice truss construction
Bridges, Fig. 21 Covered Partridge truss
of the most common types of covered bridges. Many later
covered bridge truss types used an added arch based on the
success of the Burr truss (Fig. 17).
The Town lattice truss patented in 1820 by Ithiel Town is
constructed of planks rather than the heavy timbers required
in Kingpost and Queenpost designs. It was easy to construct,
but tedious. Reportedly, Mr. Town licensed his design at one
dollar per foot – or two dollars per foot for those found not
under license. The second Ft. Wayne railroad bridge over the
Allegheny River was an unusual instance of a Town lattice
constructed in iron (Fig. 18).
Herman Haupt designed and patented his truss configuration in 1839. He was in engineering management for several
railroads including the Pennsylvania Railroad (1848) and
drafted as superintendent of military railroads for the Union
Army during the Civil War. The Haupt truss concentrates
much of its compressive forces through the end panels and
onto the abutments (Fig. 19).
Other bridge designers were busy in the Midwest. An Ohio
DOT web page cites examples of designs used for some
covered bridges in that state. Robert W. Smith of Tipp City,
OH, received patents in 1867 and 1869 for his designs. Three
variations of the Smith truss are still standing in Ohio covered
bridges (Fig. 20).
Reuben L. Partridge received a patent for his truss design
that appears to be a modification of the Smith truss (Fig. 21).
Four of the five Partridge truss bridges near his home in
Marysville, Union County, OH, are still in use.
Bridges, Fig. 22 Covered Childs truss
Horace Childs’ design of 1846 was a multiple kingpost with
the addition of iron rods (Fig. 22). The Childs’ truss was used
exclusively by Ohio bridge builder Everett Sherman after 1883.
Pratt Truss Variations
The Pratt truss is a very common type, but has many variations. Originally designed by Thomas and Caleb Pratt in
1844, the Pratt truss successfully made the transition from
wood designs to metal. The basic identifying features are the
diagonal web members that form a V-shape. The center section commonly has crossing diagonal members. Additional
counter braces may be used and can make identification more
difficult, but the Pratt and its variations are the most common
type of all trusses.
Charles H. Parker modified the Pratt truss to create a
“camelback” truss having a top chord that does not stay
parallel with the bottom chord. This creates a lighter structure
without losing strength; there is less dead load at the ends and
more strength concentrated in the center. It is somewhat more
complicated to build since the web members vary in length
from one panel to the next.
84
Bridges
Bridges, Fig. 24 Whipple truss variations
Bridges, Fig. 23 Types of Pratt truss variations
When additional smaller members are added to a Pratt
truss, the various subdivided types have been given names
from the railroad companies that most commonly used each
type, although both were developed by engineers of the
Pennsylvania Railroad in the 1870s (Fig. 23).
The Whipple truss was developed by Squire Whipple as
stronger version of the Pratt truss. Patented in 1847, it is also
known as the “Double-intersection Pratt” because the diagonal tension members cross two panels, whereas those on the
Pratt cross one. The Indiana Historical Bureau notes one
bridge as being a “Triple Whipple” – possibly the only
one – built with the thought that if two are better than one,
three must be stronger yet. The Whipple truss was most
commonly used in the trapezoidal form – straight top and
bottom chords – although bowstring Whipple trusses were
also built. The Whipple truss gained immediate popularity
with the railroads as it was stronger and more rigid than the
Pratt. It was less common for highway use, but a few wrought
iron examples survive. They were usually built where the
span required was longer than was practical with a Pratt
truss (Fig. 24). Further developments of the subdivided variations of the Pratt, including the Pennsylvania and Baltimore
trusses, led to the decline of the Whipple truss.
Warren Truss Variations
A Warren truss, patented by James Warren and Willoughby
Monzoni of Great Britain in 1848, can be identified by the
presence of many equilateral or isosceles triangles formed by
the web members that connect the top and bottom chords.
These triangles may be further subdivided (Fig. 25). Warren
truss designs may also be found in covered bridge designs.
Bridges, Fig. 25 Warren truss variations
Truss: Other Types
The other truss types discussed are less common on modern
bridges. A Howe truss at first appears similar to a Pratt truss,
but the Howe diagonal web members are inclined toward the
center of the span to form A-shapes. The vertical members are
in tension, whereas the diagonal members are in compression,
exactly opposite the structure of a Pratt truss. Patented in 1840
by William Howe, this design was common on early railroads. The three drawings show various levels of detail
(Fig. 26). The thicker lines represent wood braces; the
thinner lines are iron tension rods. The Howe truss was
patented as an improvement to the Long truss that is discussed
with covered bridge types.
Friedrich August von Pauli (1802–1883) published details
of his truss design in 1865. Probably the most famous example of the Pauli truss, better known as the lenticular
truss – named because of the lens shape – is Pittsburgh’s
Smithfield Street Bridge (Fig. 27). Its opposing arches
combine the benefits of a suspension bridge with those of an
Bridges
85
B
Bridges, Fig. 28 Wichert truss details
Bridges, Fig. 26 Howe truss details
Bridges, Fig. 27 Lenticular truss details
arch bridge. But like a willow tree, some of its strength is
expressed in its flexibility which is often noticeable to bridge
traffic.
Before the use of computers, the interaction of forces on
spans that crossed multiple supports was difficult to calculate.
One solution to the problem was developed by E. M. Wichert
of Pittsburgh, PA, in 1930. By introducing an open, hinged
quadrilateral over the intermediate piers, force interaction for
each span could be calculated independently. The first
Wichert truss was the Homestead High Level Bridge over
the Monongahela River in 1937 (Fig. 28).
The composite cast and wrought iron Bollman truss was
common on the Baltimore and Ohio Railroad. Of the hundred
or so following Wendell Bollman’s design, the 1869 bridge at
Savage, MD, is perhaps the only intact survivor. Some of the
counter bracing inside the panels is absent in the drawing for
clarity (Fig. 29).
Also somewhat common on early railroads, particularly
the B&O, was the Fink truss designed by Albert Fink of
Germany in the 1860s (Fig. 30).
Cantilever Truss Types
A cantilever is a structural member that projects beyond its
support and is supported at only one end. Cantilever bridges
are constructed using trusses, beams, or girders. Employing
the cantilever principles allows structures to achieve spans
Bridges, Fig. 29 Bollman truss details
Bridges, Fig. 30 Fink truss details
Bridges, Fig. 31 Spandrel braced cantilever arch
longer than simple spans of the same superstructure type
(Fig. 31). They may also include a suspended span that
hangs between the ends of opposing cantilever arms. Some
bridges that appear to be arch type are, in fact, cantilever truss.
These may be identified by the diagonal braces that are used
in the open spandrel. A true arch bridge relies on vertical
members to transfer the load to the arch. Pratt and Warren
bracing are among the most commonly used truss types.
The classic cantilever design is the through truss that
extends above the deck. Some have trusses that extend both
above and below the deck. The truss configuration will vary
(Fig. 32).
Suspension Types
The longest bridges in the world are suspension bridges or
their cousins, the cable-stayed bridge (Fig. 33). The deck
hangs from suspenders of wire rope, eye-bars, or other materials. Materials for the other parts also vary: piers may be steel
86
Bridges
Bridges, Fig. 32 Cantilever through truss variations
or masonry; the deck may be made of girders or trussed.
A tied arch resists spreading (drift) at its bearings by using
the deck as a tie piece.
Though the city of Pittsburgh has been a pioneer in bridge
design and fabrication, it has had few suspension bridges.
The Pennsylvania Mainline Canal entered the city on John
Roebling’s first wire-rope suspension bridge in 1845
(replacing a failing 1829 wooden structure). A similar structure still stands at Minnisink Ford, NY, crossing the Delaware
River. Roebling and his son Washington Roebling, later
famous in building the Brooklyn Bridge, began their work
in Saxonburg, PA, north of Pittsburgh.
New Developments in Bridge Engineering
The latest advancements in bridge engineering are coming on
several fronts, which include rapid and robust construction/
deployment techniques, new innovative materials, analysis
and design procedures, etc. In the past, bridge bearings used
to be the inevitable component of bridges. However, of-late
integral bridges have been introduced, in which the conventional superstructure and substructure are integral with each
other. Extra-dosed bridges are yet another new approach of
bridge design evolving from the cable-stayed bridge and
cantilever-girder bridge, wherein the pylon heights are
lowered significantly and the stay-cables are provided more
parallel to the bridge girder.
Novel materials have been introduced in bridge constructions, which are lighter but relatively stronger. For example,
the steel reinforcements are replaced with the fiber-reinforced
polymer (FRP) bars. In addition to their high strength to
weight ratio, the FRP reinforcements also offer advantages
such as noncorrosiveness and durability, low thermal conductivity, nonconduction to electricity, and nonmagnetic. In cold
countries, especially, where extensive de-icing salts are used,
the steel employed in the bridge construction is highly susceptible to corrosion. In such situations, the noncorrosive
FRP reinforcements offer an attractive alternative to the
bridge designers. Wide varieties of the FRP reinforcements
Bridges, Fig. 33 Types of suspension bridges
are now available, made from fibers of glass, carbon, basalt,
etc. For instance, carbon fiber reinforced polymer (CFRP)
PSC bridges have been successfully constructed in the USA
(Grace et al. 2010a, b, 2013a, b). However, it is argued that the
CFRP reinforcements are relatively much expensive, which
considerably increase the cost of the bridge construction.
Nevertheless, it has been plausibly established that the
CFRP-PSC bridges are cost-effective over their life-cycle
(Grace et al. 2010c). The FRPs are also available in different
forms such as rods, cables/strands, fabric, laminates. Some of
these FRP materials are used in retrofitting and rehabilitation
of the bridges.
Resiliency of bridges has become an important concern,
especially in earthquake-prone areas. It defines how quickly a
seismically damaged bridge can be restored to its functional
use. Some advanced dynamic response control devices, such
as base isolation and tuned mass dampers, have been proposed to effectively limit the forces induced in bridges
because of earthquakes and strong winds or enhance their
seismic performance (Matsagar and Jangid 2006; Matin
et al. 2017; Elias and Matsagar 2017). Furthermore, in those
areas that experience more than one hazard, the bridges are
analyzed for multihazard effects. For example, during flood,
the bed erosion may cause increase in the effective length of
the bridge piers. Thus, the load-carrying capacity of the
bridge reduces significantly, refer to Eq. 2. When such a
bridge is subjected to earthquake ground motion, it is seismically more vulnerable. Therefore, multihazard resiliency is
routinely investigated for the bridges. Real-time remote/automated health monitoring of bridges; system identification and
Bridges
87
nondestructive testing; rapid inspection, assessment, and
maintenance methods; and improved safety, risk, and resilience quantification of bridges and their networks have been
the latest topics of greater research interest and field implementation in bridge engineering.
Baltimore
truss
Summary
Beginning from the inception of bridge engineering, the essential parts of bridges and their components have been identified
and discussed. Crucial stages in bridge planning, analysis, and
design were explained from the perspective of engineering
geology. The usefulness of engineering geology during the
planning, analysis, and design stages of a bridge is evident at
all stages. Finally, the latest advancements and technological
developments in bridge engineering have been summarized.
Bascule
Bridge
Beam
Cross-References
▶ Casing
▶ Cofferdam
Bearing
Appendix
Bent
Abutment
Anchor span
Anchorage
Aqueduct
Arch
Arch barrel
Arch ring
Balustrade
Part of a structure that supports the end of a
span or accepts the thrust of an arch; often
supports and retains the approach
embankment.
Located at the outermost end, it
counterbalances the arm of span extending
in the opposite direction from a major point
of support. Often attached to an abutment.
Located at the outermost ends, the part of a
suspension bridge to which the cables are
attached. Similar in location to an abutment
of a beam bridge.
A pipe or channel, open or enclosed, which
carries water. May also be part of a canal to
carry boats. Sometimes carried by a bridge.
A curved structure that supports a vertical
load mainly by axial compression.
The inner surface of an arch extending the
full width of the structure.
An outer course of stone forming the arch.
Made of a series of voussoirs. An archivolt
is an arch ring with decorating moldings.
A decorative railing, especially one
constructed of concrete or stone, including
the top and bottom rail and the vertical
Bowstring
truss
Box girder
Brace-ribbed
arch (trussed
arch)
Buttress
supports called balusters. May also include
larger vertical supports called stanchions.
A subdivided Pratt truss commonly
constructed for the Baltimore and Ohio
Railroad. It has angled end posts and a top
chord that is straight and horizontal.
Compare to camelback truss and
Pennsylvania truss.
From the French word for “see-saw,” a
bascule bridge features a movable span
(leaf) which rotates on a horizontal hinged
axis (trunnion) to raise one end vertically.
A large counterweight offsets the weight of
the raised leaf. May have a single raising
leaf or two that meet in the center when
closed. Compare to swing bridge and
vertical lift bridge.
A horizontal structure member supporting
vertical loads by resisting bending. A girder
is a larger beam, especially when made of
multiple plates. Deeper, longer members
are created by using trusses.
A device at the ends of beams placed on top
of a pier or abutment. The ends of the beam
rest on the bearing.
Part of a bridge substructure. A rigid frame
commonly made of reinforced concrete or
steel that supports a vertical load and is
placed transverse to the length of a
structure. Bents are commonly used to
support beams and girders. An end bent is
the supporting frame forming part of an
abutment. Each vertical member of a bent
may be called a column, pier, or pile. The
horizontal member resting on top of the
columns is a bent cap. The columns stand
on top of some type of foundation or footer
that is usually hidden below grade. A bent
commonly has at least two or more vertical
supports. Another term used to describe a
bent is capped pile pier. A support having a
single column with bent cap is sometimes
called a “hammerhead” pier.
A truss having a curved top chord and
straight bottom chord meeting at each end.
A steel beam built-up from many shapes to
form a hollow cross-section.
An arch with parallel chords connected by
open webbing.
A wall projecting perpendicularly from
another wall that prevents its outward
B
88
Cable
Cable-stayed
bridge
Camber
Camelback
truss
Cantilever
Castellated
girder
Catenary
Centering
Chord
Column
Continuous
span
Corbelled arch
Bridges
movement. Usually wider at its base and
tapering toward the top.
Part of a suspension bridge extending from
an anchorage over the tops of the towers
and down to the opposite anchorage.
Suspenders or hangers attach along its
length to support the deck.
A variation of suspension bridge in which
the tension members extend from one or
more towers at varying angles to carry
the deck. Allowing much more freedom in
design form, this type does not use cables
draped over towers, nor the anchorages at
each end, as in a traditional suspension
bridge.
A positive, upward curve built into a beam
that compensates for some of the vertical
load and anticipated deflection.
A truss having a curved top chord and
straight bottom chord meeting at each end,
especially when there are more than one
used end to end. Compare to Baltimore
truss and Pennsylvania truss.
A structural member that projects beyond a
supporting column or wall and is
counterbalanced and/or supported at only
one end.
A steel beam fabricated with a zig-zag cut
along its web, and welding the two sides
together at their peaks. This creates a beam
that has increased depth and therefore
greater strength, but not increased weight.
Curve formed by a rope or chain hanging
freely between two supports. The curved
cables or chains used to support suspension
bridges are called catenaries.
Temporary structure or false-work
supporting an arch during construction.
Either of the two principal members of a
truss extending from end to end, connected
by web members.
A vertical structural member used to
support compressive loads. See also pier
and pile.
A superstructure that extends as one piece
over multiple supports.
Masonry built over an opening by
progressively overlapping the courses from
each side until they meet at the top center.
Not a true arch as the structure relies on
strictly vertical compression, not axial
compression.
Counter
Cradle
Cripple
Crown
Culvert
Deck
Deck truss
Elliptical arch
Embankment
End post
Expansion
joint
Extrados
Eye bar
False-work
Fill
Finial
Fixed arch
Floor beam
A truss web member that functions only
when a structure is partially loaded.
Part of a suspension bridge that carries the
cable over the top of the tower.
A structural member that does not extend
the full height of others around it and does
not carry as much load.
On road surfaces, where the center is the
highest point and the surface slopes
downward in opposite directions, assisting in
drainage. Also a point at the top of an arch.
A drain, pipe, or channel that allows
water to pass under a road, railroad, or
embankment.
The top surface of a bridge that carries the
traffic.
A truss that carries its deck on its top chord.
Compare to pony truss and through truss.
An arch formed by multiple arcs each
drawn from its own center. Compare to a
roman arch that is a semi-circular arc drawn
from a single center-point.
Angled grading of the ground.
The outward-most vertical or angled
compression member of a truss.
A meeting point between two parts of a
structure which is designed to allow for
movement of the parts due to thermal or
moisture factors while protecting the parts
from damage. Commonly visible on a
bridge deck as a hinged or movable
connection.
The outer exposed curve of an arch; defines
the lower arc of a spandrel.
A structural member having a long body
and an enlarged head at each end. Each
head has a hole through which an inserted
pin connects to other members.
Temporary structure used as support during
construction. False-work for arch
construction is called “centering.”
Earth, stone, or other material used to raise
the ground level, form an embankment, or
fill the inside of an abutment, pier, or closed
spandrel.
A sculpted decorative element placed at the
top of a spire or highpoint of a structure.
A structure anchored in its position.
Compare to hinged arch.
Horizontal members that are placed
transversely to the major beams, girders, or
trusses, used to support the deck.
Bridges
Footing
Gabion
Girder
Gusset plate
Haunch
Hinged arch
Howe truss
Humpback
Impost
Intrados
Jersey barrier
Keystone
King Truss
89
The enlarged lower portion of the
substructure or foundation that rests
directly on the soil, bedrock, or piles;
usually below grade and not visible.
A galvanized wire box filled with stones
used to form an abutment or retaining wall.
A horizontal structure member supporting
vertical loads by resisting bending. A girder
is a larger beam, especially when made of
multiple metal plates. The plates are usually
riveted or welded together.
A metal plate used to unite multiple
structural members of a truss.
The enlarged part of a beam near its
supported ends that results in increased
strength; visible as the curved or angled
bottom edge of a beam.
A two-hinged arch is supported by a pinned
connection at each end. A three-hinged arch
also includes a third pinned connection at
the crown of the arch near the middle of a
span. Compare to fixed arch.
A type of truss in which vertical web
members are in tension and diagonal web
members in compression. Maybe
recognized by diagonal members that
appear to form an “A” shape (without the
crossbar) toward the center of the truss
when viewed in profile. Compare to Pratt
truss and Warren truss.
A description of the side-view of a bridge
having relatively steep approach
embankments leading to the bridge deck.
The surface that receives the vertical weight
at the bottom of an arch.
The interior arc of an arch.
A low, reinforced concrete wall wider at the
base, tapering vertically to near mid-height
and then continuing straight up to its top.
The shape design directs automotive traffic
back toward its own lane of travel and
prevents crossing of a median or leaving the
roadway. Commonly used on new and
reconstructed bridges in place of decorative
balustrades, railings, or parapets.
The uppermost wedge-shaped voussoir at
the crown of an arch that locks the other
voussoirs into place.
Two triangular shapes sharing a common
center vertical member (king post); the
simplest triangular truss system. Compare
to queen truss.
Knee brace
Lag
Lateral
bracing
Lattice
Lenticular
truss
Member
Parabola
Parapet
Pennsylvania
truss
Pier
Pile
Pin
Pony truss
Portal
Additional support connecting the deck
with the main beam that keeps the beam
from buckling outward. Commonly made
from plates and angles.
Crosspieces used to connect the ribs in
centering.
Members used to stabilize a structure by
introducing diagonal connections.
An assembly of smaller pieces arranged in a
grid-like pattern; sometimes used a
decorative element or to form a truss of
primarily diagonal members.
A truss that uses curved top and bottom
chords placed opposite one another to form
a lens shape. The chords are connected by
additional truss web members.
One of many parts of a structure, especially
one of the parts of a truss.
A form of arch defined by a moving point
that remains equidistant from a fixed point
inside the arch and a moving point along a
line. This shape when inverted into an arch
structure results in a form that allows equal
vertical loading along its length.
A low wall along the outside edge of a
bridge deck used to protect vehicles and
pedestrians.
A subdivided Pratt truss invented for use by
the Pennsylvania Railroad. The
Pennsylvania truss is similar in bracing to a
Baltimore truss, but the former has a
camelback profile, whereas the latter has
angled end posts only, leaving the upper
chord straight and horizontal. Compare to
camelback truss and Baltimore truss.
A vertical structure that supports the ends of a
multispan superstructure at a location between
abutments. See also column and pile.
A long column driven deep into the ground
to form part of a foundation or substructure.
See also column and pier.
A cylindrical bar used to connect various
members of a truss; such as those inserted
through the holes of a meeting pair of
eye-bars.
A truss that carries its traffic near its top chord
but not low enough to allow cross-bracing
between the parallel top chords. Compare to
deck truss and through truss.
The opening at the ends of a through truss
that forms the entrance. Also the open
entrance of a tunnel.
B
90
Post
Pratt truss
Pylon
Queen Truss
Reinforcement
Revet
Revetment
Rib
Rigid Frame
Bridge
Rise
Segmental
arch
Simple span
Bridges
One of the vertical compression members of a
truss that is perpendicular to the bottom chord.
A type of truss in which vertical web
members are in compression and diagonal
web members in tension. Many possible
configurations include pitched, flat, or
camelback top chords. Maybe be
recognized by diagonal members which
appear to form a “V” shape toward the
center of the truss when viewed in profile.
Variations include the Baltimore truss and
Pennsylvania truss. Compare to Warren
truss and Howe truss.
A monumental vertical structure marking
the entrance to a bridge or forming part of a
gateway.
A truss having two triangular shapes spaced
on either side of central apex connected by
horizontal top and bottom chords. Compare
to king truss.
Adding strength or bearing capacity to a
structural member. Examples include the
placing of metal rebar into forms before
pouring concrete, or attaching gusset plates
at the intersection of multiple members of a
truss.
The process of covering an embankment
with stones.
A facing of masonry or stones to protect an
embankment from erosion.
Any one of the arched series of members
that is parallel to the length of a bridge,
especially those on a metal arch bridge.
A type of Girder Bridge in which the piers
and deck girder are fastened to form a
single unit. Unlike typical girder bridges
constructed so that the deck rests on
bearings atop the piers, a rigid frame bridge
acts as a unit. Pier design may vary.
The measure of an arch from the spring line
to the highest part of the intrados, that is
from its base support to the crown.
An arch formed along an arc drawn from a
point below its spring line, thus forming a
less than semi-circular arch. The intrados of
a Roman arch follows an arc drawn from a
point on its spring line, thus forming a
semi-circle.
A span in which the effective length is the
same as the length of the spanning
structure. The spanning superstructure
extends from one vertical support,
Skew
Span
Spandrel
Splice plate
Springer
Spring line
Stanchion
Stiffener
Stringer
Strut
Substructure
Superstructure
Suspended
span
Suspenders
Suspension
bridge
abutment, or pier, to another, without
crossing over an intermediate support or
creating a cantilever.
When the superstructure is not
perpendicular to the substructure, a skew
angle results. The skew angle is the acute
angle between the alignment of the
superstructure and the alignment of the
substructure.
The horizontal space between two supports
of a structure. Also refers to the structure
itself. The clear span is the space between
the inside surfaces of piers or other vertical
supports. The effective span is the distance
between the centers of two supports.
The roughly triangular area above an arch
and below a horizontal bridge deck.
A closed spandrel encloses fill material.
An open spandrel carries its load using
interior walls or columns.
A plate that joins two girders. Commonly
riveted or bolted.
The first voussoir resting on the impost of
an arch.
The place where an arch rises from its
support; a line drawn from the impost.
One of the larger vertical posts supporting a
railing. Smaller, closely spaced vertical
supports are balusters. See also balustrade.
On plate girders, structural steel shapes,
such as an angle, are attached to the web to
add intermediate strength.
A beam aligned with the length of a span
that supports the deck.
A compression member.
The portion of a bridge structure including
abutments and piers that supports the
superstructure.
The portion of a bridge structure which
carries the traffic load and passes that load
to the substructure.
A simple beam supported by cantilevers of
adjacent spans, commonly connected
by pins.
Tension members of a suspension bridge
that hang from the main cable to support the
deck. Also similar tension members of an
arch bridge which features a suspended
deck. Also called hangers.
A bridge that carries its deck with many
tension members attached to cables draped
over tower piers.
Bridges
Swing Bridge
Through truss
Tie
Tied arch
Tower
Trestle
Truss
Trussed arch
Upper chord
Vault
Vertical Lift
Bridge
Viaduct
Voussoir
91
A movable deck bridge which opens by
rotating horizontally on an axis. Compare
to Bascule Bridge and vertical lift bridge.
A truss which carries its traffic through the
interior of the structure with cross-bracing
between the parallel top and bottom chords.
Compare to deck truss and pony truss.
A tension member of a truss.
An arch that has a tension member across
its base that connects one end to the other.
A tall pier or frame supporting the cable of a
suspension bridge.
While Bridge is the more general term
(which may be a single span or multi-span,
typically one span is longer than the others).
Trestle is a longer, multi-span structure - a
series of shorter spans in which most of the
spans are of similar length. Trestle is a more
common term in relation to railroads,
whereas viaduct is a similar long, multi-span
structure for streets. Neither term seems to
be exclusive. Although described as a single
structure, the Ohio Connecting RR Bridge
over the Ohio River at Brunot Island can be
described as a pair of bridges (one over each
river channel) with a trestle at each approach
and a trestle connection in the center. But
more often, a long structure which does not
have a predominantly larger span could be
described as a trestle.
A structural form which is used in the same
way as a beam, but because it is made of a
web-like assembly of smaller members it
can be made longer, deeper, and therefore,
stronger than a beam or girder while being
lighter than a beam of similar dimensions.
A metal arch bridge that features a curved
truss.
Top chord of a truss.
An enclosing structure formed by building
a series of adjacent arches.
A movable deck bridge in which the deck is
raised vertically by synchronized
machinery at each end. Compare to swing
bridge and vertical lift bridge.
A long, multispan structure, especially one
constructed of concrete. More commonly
used in relation to structures carrying motor
vehicles. Trestle is the term for a similar
structure when used in relation to railroads.
Any one of the wedge shaped block used to
form an arch.
Warren truss
Web
Wing walls
A type of truss in which vertical web
members are inclined to form equilateral
triangles. May be recognized by diagonal
members that appear to form a series of
alternating “V” and “A” shapes (without
the crossbar) along the length of the truss
when viewed in profile. Often the triangles
are bisected by vertical members to reduce
the length of the members of the top chord.
Compare to Pratt truss and Howe truss.
The system of members connecting the top
and bottom chords of a truss. Also the
vertical portion of an I-beam or girder.
Extensions of a retaining wall as part of an
abutment; used to contain the fill of an
approach embankment
References
Elias S, Matsagar V (2017) Effectiveness of tuned mass dampers in
seismic response control of isolated bridges including soil-structure
interaction. Lat Am J Solids Struct 14:2324–2341. https://doi.org/10.
1590/1679-78253893
Grace N, Jensen E, Enomoto T, Matsagar V, Soliman E,
Hanson J (2010a) Transverse diaphragms and unbonded CFRP
post-tensioning in box beam bridges. PCI J 55(2):109–122
Grace N, Jensen E, Matsagar V, Soliman E, Hanson J (2010b) Use of
unbonded CFRP strands in transverse post-tensioning in box beam
bridges. Int J Earth Sci Eng 3(2):128–137
Grace N, Jensen E, Eamon C, Shi X, Matsagar V (2010c) Life-cycle cost
analysis of CFRP reinforced concrete bridges. In: 89th annual
meeting of the Transportation Research Board (TRB), Washington
DC. https://trid.trb.org/view.aspx?id=909784
Grace N, Jensen E, Matsagar V, Penjendra P (2013a) Performance of an
AASHTO beam bridge prestressed with CFRP tendons. J Bridg Eng
18(2):110–121
Grace N, Ushijima K, Matsagar V, Wu C (2013b) Performance of
AASHTO-type bridge model prestressed with carbon fiberreinforced polymer reinforcement. ACI Struct J 110(3):491–502
Jagadeesh TR (2004) Design of bridge structures. PHI Learning Private
Limited
Lawler DM (1993) The measurement of river bank erosion and lateral
channel change: a review. Earth Surf Process Landf 18(9):777–821.
https://doi.org/10.1002/esp.3290180905
Matin A, Elias S, Matsagar V (2017) Seismic response control of
reinforced concrete bridges with soil-structure interaction. Bridg
Struct Eng 47(1):34–40. http://issuu.com/iabse.secretariat/docs/15_
2017_march_vol_47_no_1?e=6367743/49550709
Matsagar V, Jangid RS (2006) Seismic response of simply supported
base-isolated bridge with different isolators. Int J Appl Sci Eng
4(1):55–71
Moses C, Robinson D, Barlow J (2014) Methods for measuring rock
surface weathering and erosion: a critical review. Earth Sci Rev
135:141–161
Ponnuswamy S (2008) Bridge engineering, 2nd edn. Tata McGraw-Hill
Education, New York
Prendergast LJ, Gavin K (2014) A review of bridge scour monitoring
techniques. J Rock Mech Geotech Eng 6(2):138–149. https://doi.org/
10.1016/j.jrmge.2014.01.007
B
92
Brownfield Sites
Raina VK (2004) Concrete bridge practice analysis, design and economics, 3rd edn. Shroff Publishers & Distributors Private Limited,
Mumbai
Slobodan K, Ljupko R, Meri G (2012) The subsurface geology along the
route of the new bridge at Ada Ciganlija Island (Belgrade, Serbia).
Geol An Balk Poluostrva 73:9–19. http://www.doiserbia.nb.rs/img/
doi/0350-0608/2012/0350-06081273009K.pdf
Stead D, Wolter A (2015) A critical review of rock slope failure mechanisms: the importance of structural geology. J Struct Geol 74:1–23
Victor DJ (2007) Essentials of bridge engineering, 6th edn. Oxford &
IBH Publishing Company Private Limited
Brownfield Sites
Brian R. Marker
London, UK
Synonyms
Contaminated land – sometimes used as a synonym although
land that has not been used previously can also become
contaminated through water or air pollution; Derelict land;
Vacant land
Definition
Previously developed land that has become disused
(as opposed to “greenfield sites” – those that have not had
previous uses other than agriculture, forestry, or no perceptible human interventions).
Introduction
Brownfield sites are mainly located in urban areas where industrial or commercial buildings and facilities have become disused.
But some sites, such as military installations, mines, and waste
management sites, may be located in open countryside or wilderness areas. Individual sites may cover many hectares or be
small and scattered. Some can be easily redeveloped but many
have problems of contamination/pollution, instability, and
obstructions from past uses that add to difficulties and costs of
either redevelopment or rehabilitation. Surficial deposits on such
sites are often of anthropogenic origin.
Sites may be vacant (i.e., essentially intact but not in use)
or derelict (abandoned and in poor condition) or may still be
partly used (e.g., a scrap yard on a former factory site) (Fig. 1).
Contamination and Pollution
Contaminants in brownfield sites may include solids, liquids
and gases, and volatile organic compounds. The nature and
Brownfield Sites, Fig. 1 Abandoned industrial site, London, UK
(Photograph by the author)
composition of these depends on the various human activities
that have taken place. These may include hydrocarbons, solvents, pesticides, potentially harmful elements and inorganic
compounds, phenols and related compounds, cyanides and
asbestos, and, sometimes, radioactive materials or munitions.
Some are toxic, asphyxiant, or carcinogenic. Others can react
chemically with construction materials such as concrete and
metal form-work.
Treatment of contamination traditionally involved excavation and removal to landfill commonly referred to as “dig and
dump.” While that is the least expensive option, it simply
moves contaminants from one place to another. Alternatives,
which are environmentally more sustainable, but are also
usually more expensive, include:
• Soil washing – excavation of soils and washing them using
internally recycled water to avoid additional pollution, and
careful disposal of the resulting water
• In situ thermal desorption – to mobilize volatile and semivolatile organic contaminants
• Bioremediation/phytoremediation – breaking down contaminants using injected or bacteria or fungi, or by using
Brownfield Sites
deep-rooted plants to extract heavy metals and, when fully
grown, to cut these and dispose of them to landfill
• In situ chemical oxidation – injection of oxidants such as
sodium or potassium permanganate, ozone or Fenton’s
Reagent to treat or reduce the toxicity of certain organic
contaminants (e.g., benzene, toluene, and chlorinated
solvents)
• In situ soil vapor extraction – use of vacuum blowers and
extraction wells to induce gas flow through the subsurface
so that it can be collected and treated aboveground
(Meuser 2012)
Stability and Obstructions
Previously used land sometimes contains:
• Cavities such as shallow mines, cellars, and storage tanks
which may need to be excavated and/or filled and shafts
and wells that need to be capped or filled to ensure stability
• Tipped materials that may be poorly consolidated and
subject to settlement
• Foundations of previous structures and services (e.g.,
pipes and cables) that may need to be excavated and
removed
Demolition
Many sites require demolition of buildings and foundations. It
is desirable to, as far as possible, recycle debris (e.g., recovery
of metals and soils; crushing of concrete and masonry for use
as aggregates). However the components of old buildings
may be difficult to separate economically and can be further
contaminated by materials such as asbestos in which case they
must be landfilled as hazardous waste.
Conservation
Simplistically, it might be thought that brownfield sites are
environmentally undesirable and should be fully remediated
to benefit the environment, wildlife, and people. That is often
true, but there are important exceptions.
Disturbed ground that is left vacant for a protracted period
attracts plants that are adapted for invading such settings.
These form the basis of new ecosystems and can add to
local biodiversity (Angold et al. 2006). Instances are known
where deposits of particular chemical compositions have led
to unusual plant communities on sites that were of sufficient
interest for the sites to be given protected status. Therefore
collaboration between engineering geologists and ecologists
is important.
93
Some previously used land may have gone through several
rounds of development and abandonment over several hundred years, the early stages of which may now be of archaeological/industrial archaeological importance (Symonds
2010). These require collaboration between engineering geologists and archaeologists.
Investigation
Commonly, the history of a site and consequent problems are
not fully known therefore detailed site investigation is normally necessary to identify potential problems so that reliable
cost estimates for remedial works can be made. This can be
time consuming and expensive. Investigations have five main
elements:
• Examination of old maps, documents, publications, and
photographs to identify all previous uses of the site to
establish which problems may have been inherited from
these
• A “walk-over” survey and mapping of the site to observe
evidence of problems and potential advantages and to
provide the context for ground investigations
• Design of an investigation strategy
• Site investigation (trial pitting, drilling, geophysical survey, sampling, testing and monitoring)
• Preparation of a report setting out the steps and techniques
that should be adopted during site remediation and
development
Careful investigation is essential to avoid unexpected
problems during site works that add to costs and delay development. Brownfield sites may present hazards to:
• Staff undertaking site investigations, remediation or works
because of toxins, gases or, sometimes, explosives and
even old munitions
• Local communities if works lead to new contamination or
pollution of nearby soils, water, or the air
The reliability of geophysical investigations may be
affected by metal pipework and cables (some of which may
be electrically “live”) (Nathanail and Bardos 2004).
Care is needed in site evaluations and operations to confine
and minimize risks.
Affordability
Remediation of brownfield sites is usually more, and
sometimes prohibitively, expensive than developing greenfield sites making these less attractive to developers. But
B
94
making use of brownfield sites is often needed to improve
derelict land and minimize damage to undeveloped land
(de Sousa 2000).
In several countries, the amounts and types of brownfield
land are monitored together with progress on redevelopment.
In some cases, registers are kept that developers can use to
identify sites for possible redevelopment.
Various measures have been developed to incentivize the
re-use of brownfield land, for example:
• Collaborations between private companies and insurance
companies to underwrite clean-up, guarantee clean-up
costs, and limit the exposure of developers to environmental costs and litigation (USA).
• Site assessment using public money to provide certainty to
prospective developers (USA).
• Tax incentives.
• Grants paid by Government to offset costs of remediation
(UK).
Building Stone
References
Angold PG, Sadler JP, Hill MO, Pullin A, Rushton S, Austin K,
Small E, Wood B, Wadsworth R, Sanderson R, Thompson K
(2006) Biodiversity in urban habitat patches. Sci Total Environ
360(1–3):196–204. https://doi.org/10.1016/j.scitotenv.2005.08.035
de Sousa C (2000) Brownfield development versus greenfield development: a private sector perspective on the costs and risks associated
with brownfield development in the greater Toronto area. J Environ
Plann Manag 43(6):831–853. https://doi.org/10.1080/09640560020
001719
Meuser H (2012) Soil remediation and rehabilitation: treatment of
contaminated and disturbed land. Environmental pollution no.23.
Springer Science and Business Media, Dordrecht, 408 pp
Nathanail CP, Bardos P (2004) Reclamation of contaminated land.
Wiley, Hoboken, 250 pp
Symonds J (2010) Historical archaeology and the recent urban past.
Int J Herit Dent Stud 10(1):33–48. https://doi.org/10.1080/135272
5032000194231
Building Stone
• All possible subsequent uses
• Some specific uses following remedial action
Maria Heloisa Barros de Oliveira Frascá1 and
Cid Chiodi Filho2
1
MHB Geological Services, São Paulo, SP, Brazil
2
Kistemann and Chiodi – Consultancy and Projects, Belo
Horizonte, MG, Brazil
The former is usually much more expensive, so the latter is
more often adopted.
Synonyms
There have been two main philosophies for remediation- to
make the site safe for:
Dimension stone; Natural stone
Summary
Previously developed land often presents problems of contamination, pollution, and instability, which makes it costly to
redevelop compared with greenfield sites. Even so, public
policies often favor the redevelopment of brownfield land
over use of new sites. This usually requires the provision of
incentives to developers from public authorities. Redevelopment requires careful site investigation followed by cautious
redevelopment to prevent the possibility of contamination/
pollution spreading.
Cross-References
▶ Artificial Ground
▶ Contamination
▶ Drilling Hazards
▶ Foundations
▶ Gases
▶ Monitoring
▶ Site Investigation
▶ Waste Management
Definition
Building stone is a generic term referring to all naturally
occurring rock (natural stone as defined by BSI 2002) used in
the building construction industry, including a wide variety of
igneous, sedimentary, and metamorphic rocks. If after quarrying, the rock has been selected and cut to specific sizes and
shapes, it is referred as dimension stone (ASTM 2016).
The availability and durability of stones has made them a
major contributor to the legacy of human history. Stones were
widely used as structural elements, mostly as irregularly
shaped large blocks usually closely fitted (without binders),
in the construction of temples, monuments, fortifications,
aqueducts, bridges, and housing.
Due to the development and technological improvement
of tools and machinery building stones are now quarried in
large scale as regularly shaped blocks that can be cut into a
wide choice of slab thicknesses and sizes (Fig. 1) and can
receive several types of finishing (polished, honed, flamed,
bush-hammered, and others). Reinforcement and filling may
be used, depending of the rock type and characteristics
Building Stone
95
B
Building Stone, Fig. 1 Modern quarrying of building stones (left) and an illustration of slabs in different dimensions according to the final use
(right)
Building Stone, Table 1 Some building stone application and laboratory testing requirements (After ASTM 2012, modified)
Laboratory testing requirements (properties)
Petrography
Bulk density
Water absorption
Thermal dilatation
Abrasion resistance
Compressive strength
Modulus of rupture
Flexural strength
Building stone application
Floors
Exterior
Interior
●
●
●
●
●
●
●
●
●
Walls
Exterior
●
●
●
●
●
Interior
●
●
Façades
●
●
●
●
●
●
●
(presence of pores, cavities, cracks, fissures). Stone processing frequently also includes resination that consists of
the cosmetic enhancement of stone slab surface by proper
resin application (epoxy, acrylic).
Current uses of natural stone in buildings include loadbearing and self-supporting masonry, masonry façades to
framed buildings, cladding and lining, flooring and stone roofing, in which slates have particular importance (Ingham 2011).
Another significant application is paving. As ornamental and
decorative pieces, they are also extensively used in countertops
and counters, sculptures, gravestones, and for landscaping.
Aesthetics, especially color, is the main attribute influencing
the architectural choice of building stones. However, it is
essential to consider their physical and mechanical properties
(also called engineering properties), that are determined by
laboratory testing, such as bulk density, water absorption, and
mechanical strength, including petrographic analysis (Table 1).
These allow to the selection of the rock type that is most
suitable to any building design and also indicate stone
●
Countertops
●
●
●
●
●
performance in diverse uses and environments. Test method
standardization is secured by statements issued by two important institutions: CEN and ASTM.
Building stones are also used to repair damaged and missing
parts of historic buildings that have undergone deterioration by
weathering or anthropogenic actions (Winkler 1997). In this
case, testing and petrographic examinations are very useful to
both diagnose the causes of stone deterioration and to identify
the most appropriate matching stones.
References
American Society for Testing and Material (2012) C1528–12 standard
guide for selection of dimension stone. ASTM, West Conshohocken, 7 p
American Society for Testing and Material (2016) C119–16 standard
terminology relating to dimension stone. ASTM, West
Conshohocken, 7 p
BSI – British Standard Institution (2002) BS EN 12670: natural
stone – terminology. BSI, London, 49 p
96
Bulk Modulus
Ingham J (2011) Geomaterials under the microscope: a colour guide,
1st edn. CRC Press/Taylor & Francis Group, Boca Raton, 192 p
Winkler EM (1997) Stone in architecture: properties, durability, 3rd edn.
Springer, Berlin, 313 p
ev ¼
1
2n
E
3p
Thus,
ev
3ð1 2nÞ
1
¼
¼
E
K
p
Bulk Modulus
K ¼
Definition
Bulk modulus (K) is the ratio of hydrostatic stress (p) on an
object to the resulting volumetric strain (ev), which is the ratio
of volume change (DV) to the initial volume (Vo).
Hydrostatic stress cannot produce shear stress; however,
principal stress acting in one direction produces strain in all
three directions, as described by Hooke’s law and Poisson’s
ratio (n). Therefore,
ex ¼
sx
E
n
sy
E
sx sy
þ
E
E
ey ¼
n
ez ¼
sx
n
E
n
(1)
sz
E
(2a)
sz
E
(2b)
sy sz
n þ
E
E
(2c)
n
E
3ð 1
2nÞ
; 0 < n < 0:5
(6)
Bulk modulus can be calculated from two basic
elastic properties: Young’s modulus and Poisson’s ratio.
A singularity in K occurs at n = 0.5, which pertains to
“incompressible” materials (Mott et al. 2008) but is not relevant in real materials of interest to engineering geologists.
Cross-References
▶ Hooke’s Law
▶ Poisson’s Ratio
▶ Strain
▶ Stress
▶ Young’s Modulus
References
where E is the Young’s modulus. Combining Eqs. 1 and 2a, b, c
2n
1
sx þ sy þ s z
sx þ sy þ sz
E
E
1 2n
s x þ sy þ sz
¼
E
(5)
and
Jeffrey R. Keaton
Amec Foster Wheeler, Los Angeles, CA, USA
ev ¼ e x þ e y þ ez
(4)
ev ¼
(3)
Hydrostatic stress is a principal stress acting equally in all
directions (p = sx = sy = sz); therefore,
Mott PH, Dorgan JR, Roland CM (2008) The bulk modulus and
Poisson’s ratio of “incompressible” materials. J Sound Vib
312:572–575
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