Papers by Stanciucu M Mihaela
IntechOpen eBooks, Mar 19, 2024
Often referred to as expansive soils in international literature, soils with large swelling and s... more Often referred to as expansive soils in international literature, soils with large swelling and shrinking potential, are defined as natural materials that exhibit volume variations related to variations of moisture. Most professionals consider that the expansive manifestations are related to the mineralogic composition, especially with the presence of the smectite class of minerals, more specifically with the montmorillonite. Despite sustained worldwide studies over decades, the direct and firm correlation between the number of clayey minerals and expansive properties has not reached a conclusive form, and the behavior of expansive soils remains still unrevealed and exhibits unexpected features under moistening or drying conditions in natural habit, or in relation with infrastructure works. This chapter presents the results of an extended and complex geotechnical investigation of expansive soils which concludes with the validation of a simple procedure of identification of the areas where the swelling behavior of soils may exceed the equilibrium of the geological structure and produce a variety of effects such as lumps or landslides in areas with sloping terrain.
Encyclopedia of earth sciences, 2018
Definition An unstratified aeolian deposit composed largely of silt-size grains that are loosely ... more Definition An unstratified aeolian deposit composed largely of silt-size grains that are loosely cemented by calcium carbonate. Loess formations cover more than 10% of the land surface of the world in both Northern Hemisphere between 25 o-55 o N (China, Siberia, Paris and Danube Basins) and Southern Hemisphere between 30 o-40 o S (Uruguay, Argentina, New Zealand). This peculiar type of sedimentary deposit, worldwide has similar characteristics which derive from aeolian deposition and has variable thickness from decimetres to tens of metres. Natural slopes are almost vertical and in arid conditions may attain 300-500m (Derbyshire, 1983; Liu, 1985). Often, loess sequences contain rustcoloured paleosol intercalations which contrast with yellowish loess deposits. The mineralogical composition of loess depends on the source of the dust and may contain 40 to 60 minerals grouped in two classes (Howayek et.al., 2011): passive ones (quartz, feldspar, mica, heavy minerals) and active minerals (carbonates, sulphates, readily soluble salts, soluble oxides and hydroxides and clay minerals). The most prevalent and active is calcium carbonate that can be present as cementing bonds of grains, as disseminations, depositions on fissures and loess-dolls (concretions of nodules). Most frequently, loess deposits are made mainly of silt fraction (>60%). If clay or sand contents exceed 20%, deposits are named clayey or sandy loess. Grains of silt or sand are bonded by four types of forces (Osipov and Sokolov, 1994): molecular, ionic-electrostatic, capillary and chemical, which are either unstable or dependent on water saturation. Loess deposits have, beside inter-grain or inter-aggregate pores, additional macro-pores, mostly extending vertically. This specific feature (named an open metastable structure) leads to unique physical properties such as low dry densities (1.155-1.4 g/cm 3), high anisotropic porosity (40-70%) and low compressive strength. The most characteristic mechanical feature derived from macropore structure and weak bonding systems is collapsibility, which is the property of being stable in unsaturated conditions but to exhibit appreciable volume changes and alteration of physical properties in the saturated state (reduction of cohesion by 2/3 parts), under static external loading and sometimes even under its proper supplementary weight. The measure of the collapsibility is the difference between settlements measured in dry and wet conditions during a double-oedometric test. For reference loading pressures of 200-300KPa, this parameter (collapse index Ie/Im) may, in severe cases, achieve levels of 10-18%. Rain or irrigation waters may easily infiltrate loess formations through vertical fissures and the descending water movement is frequently aided by vertical macropores. Temporary suspended aquifers may subsist in rainy seasons allowing groundwater to dissolve soluble minerals, to hydrodynamically detach insoluble particles and to create wells, pipes, ravines, sinkholes and gully erosion (see figure 1 modified after Billard et.al., 1993). In thick loess deposits, this phenomenon can produce systems of large subsurface pipes, tunnels and caves, named "loess pseudokarst". In some cases when loess formations serve as foundation terrain or construction material, in the absence of special design measures, these deposits may be hazardous, producing failure of engineering structures or huge flow slides (e.g. Teton Dam, Idaho, USA 1976; numerous earthquake induced landslide in Gansu Province, China, 1920).
Engineering Geology for Society and Territory - Volume 5, 2014
Liquefaction is defined as the transformation of a granular material from a solid to a liquefied ... more Liquefaction is defined as the transformation of a granular material from a solid to a liquefied state as a consequence of increased pore-water pressure and reduced effective stress (Marcuson 1978). Geological criteria have a strong influence on the liquefaction susceptibility. Saturated soil deposits that have been created by sedimentation in rivers and lakes (fluvial, alluvial deposits), or deposits formed by wind action (aeolian deposits) can be very susceptible to liquefaction. Also, soils composed of particles that are all about the same size are more susceptible to liquefaction than soils with a wide range of particle sizes. In Romania, this phenomenon is less discussed, even if it was recognized since the seismic events of 1940 (Mw = 7.7) and 1977 (Mw = 7.5). Using eight selected criteria, the susceptibility to liquefaction has been evaluated in a central area of Bucharest, which is situated into a high seismic intensity area (VIII on MSK scale), is overlaid by Holocene alluvial plain and terrace deposits and has always the water table is near surface.
Springer eBooks, Aug 26, 2014
Liquefaction is defined as the transformation of a granular material from a solid to a liquefied ... more Liquefaction is defined as the transformation of a granular material from a solid to a liquefied state as a consequence of increased pore-water pressure and reduced effective stress (Marcuson 1978). Geological criteria have a strong influence on the liquefaction susceptibility. Saturated soil deposits that have been created by sedimentation in rivers and lakes (fluvial, alluvial deposits), or deposits formed by wind action (aeolian deposits) can be very susceptible to liquefaction. Also, soils composed of particles that are all about the same size are more susceptible to liquefaction than soils with a wide range of particle sizes. In Romania, this phenomenon is less discussed, even if it was recognized since the seismic events of 1940 (Mw = 7.7) and 1977 (Mw = 7.5). Using eight selected criteria, the susceptibility to liquefaction has been evaluated in a central area of Bucharest, which is situated into a high seismic intensity area (VIII on MSK scale), is overlaid by Holocene alluvial plain and terrace deposits and has always the water table is near surface.
in Encyclopedia of Engineering Geology. Springer International Publishing AG. P.T. Bobrowsky, B. Marker (eds.), , 2017
Definition Essentially, bedrock consists of "soils and rocks that were in place before the Quater... more Definition Essentially, 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 2 million years, exposed at the Earth 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 formation if these were 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 superficial deposits"(see Fig.1).
Encyclopedia of Earth Sciences Series, 2018
Capillarity in soils refers to the upward water flow above the groundwater table. This natural ph... more Capillarity in soils refers to the upward water flow above the groundwater table. This natural phenomenon of prevailing ascent movement of water in soil pores was associated, from the first decades of research, with the capillary rise of water in fine bore tubes (Fredlund and Rahardj, 1993). In order to describe this state of water movement in soils, a capillary model must be defined throught capillary height and capillary pressure (see figure). The length of capillary rise of pure water in thin glass tubes may be expresses in terms of equilibrium between the vertical resultant of the surface tension (T s) and the weight of the water column and depend mainly on hygroscopic properties of the water and on the radius of the tube (r) (i.e. h c =2T s /(γ w r). In the case of soils, the maximum capillarity height is influenced mainly by the matric suction, the distribution of effective porosity, which is a function of grain size distribution and some physical properties of the water (temperature, mineralisation). Typical values of h c varies between 0,10-0,30m for the coarse sands and >2m for fine soils. The phenomenon evolve with a continuum decreasing rate and may last months if water supply conditions remain unchanged. The capillary moisture decrease from a full degree of saturation near the contact with water table level, to a minimum irreducible degree at h c level. Early studies (Hogentogler and Barber, 1941; Florea, 1980) demonstrate that on the first quarter of h c , the high degree of saturation allows the mass transfer of capillary water and thus an unsaturated flow toward distal parts of the layer. This phenomenon called "siphon effect" or "capillary flow" may damage downstream slopes of earth dams or tailings dams despite of the apparent stabilizing effect of capillary saturation (i.e. increasing compression of the soil structure and consequently of the shear strength due to matric suction). Capillary pressures developed inside soil structure during rising of the water, are exposed in (c) section of the figure. Based on the hydrostatic equilibrium of points A and C the matric suction is defined as the difference between poreair and pore-water pressures acting on the contractile skin (interface air-water u a-u w ; u a =atmospheric air pressure; u w =water pressure) (Fredlund and Rahardj, 1993). Thus defined, the matric suction is the main factor affecting matric potential gradient (Ψ m) responsible beside gravitational potential (Ψ g) for the unsaturated water flow on both vertical and horizontal directions. This parameter is also involved in evaluation of hydraulic conductivity of unsaturated soils (Brooks and Corey, 1966; van Genuchten, 1980). The matric suction in soils may attain thousands of KPa for which the main measuring devices are: tensiometers, null-type pressure plate, thermal conductivity sensors and pore fluid squeezer.
Encyclopedia of Earth Sciences Series, 2018
A series of rock-joint behavior routines which, briefly stated, allow the shear strength and norm... more 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,
Encyclopedia of earth sciences, 2018
Capillarity in soils refers to the upward water flow above the groundwater table. This natural ph... more Capillarity in soils refers to the upward water flow above the groundwater table. This natural phenomenon of prevailing ascent movement of water in soil pores was associated, from the first decades of research, with the capillary rise of water in fine bore tubes (Fredlund and Rahardj, 1993). In order to describe this state of water movement in soils, a capillary model must be defined throught capillary height and capillary pressure (see figure). The length of capillary rise of pure water in thin glass tubes may be expresses in terms of equilibrium between the vertical resultant of the surface tension (T s) and the weight of the water column and depend mainly on hygroscopic properties of the water and on the radius of the tube (r) (i.e. h c =2T s /(γ w r). In the case of soils, the maximum capillarity height is influenced mainly by the matric suction, the distribution of effective porosity, which is a function of grain size distribution and some physical properties of the water (temperature, mineralisation). Typical values of h c varies between 0,10-0,30m for the coarse sands and >2m for fine soils. The phenomenon evolve with a continuum decreasing rate and may last months if water supply conditions remain unchanged. The capillary moisture decrease from a full degree of saturation near the contact with water table level, to a minimum irreducible degree at h c level. Early studies (Hogentogler and Barber, 1941; Florea, 1980) demonstrate that on the first quarter of h c , the high degree of saturation allows the mass transfer of capillary water and thus an unsaturated flow toward distal parts of the layer. This phenomenon called "siphon effect" or "capillary flow" may damage downstream slopes of earth dams or tailings dams despite of the apparent stabilizing effect of capillary saturation (i.e. increasing compression of the soil structure and consequently of the shear strength due to matric suction). Capillary pressures developed inside soil structure during rising of the water, are exposed in (c) section of the figure. Based on the hydrostatic equilibrium of points A and C the matric suction is defined as the difference between poreair and pore-water pressures acting on the contractile skin (interface air-water u a-u w ; u a =atmospheric air pressure; u w =water pressure) (Fredlund and Rahardj, 1993). Thus defined, the matric suction is the main factor affecting matric potential gradient (Ψ m) responsible beside gravitational potential (Ψ g) for the unsaturated water flow on both vertical and horizontal directions. This parameter is also involved in evaluation of hydraulic conductivity of unsaturated soils (Brooks and Corey, 1966; van Genuchten, 1980). The matric suction in soils may attain thousands of KPa for which the main measuring devices are: tensiometers, null-type pressure plate, thermal conductivity sensors and pore fluid squeezer.
Encyclopedia of earth sciences, 2018
A series of rock-joint behavior routines which, briefly stated, allow the shear strength and norm... more 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,
Selective Neck Dissection for Oral Cancer, 2017
ce/papers, 2018
Loose sands or very soft clays are sometimes hard to evaluate from geotechnical purposes with cla... more Loose sands or very soft clays are sometimes hard to evaluate from geotechnical purposes with classical methods. The aim of the work is to estimate the applicability and reliability of some of the most popular relations derived from CPT in the case of marine sediments of Black Sea. The paper presents comparisons between values of main geotechnical parameters derived by well known formulas from CPT and laboratory tests executed on remoulded samples of such soils. In the first instance a classical soil behaviour chart was used in conjunction with grain size analyses. In the next step estimations of saturated or dry unit weights and friction angle of cohesionless submersed soils, based on well known relations was found in very good agreement with lab test values obtained from thin-walled tube samples. Finally, the evaluation of the state of stress puts in evidence that the investigated deposits are mainly under consolidate or normal consolidate and at least one of three different classical relations for the estimation of relative densities, fits well with values of lab tests.
MATEC Web of Conferences, 2021
Swelling and shrinking properties refers to significant positive or negative variations of volume... more Swelling and shrinking properties refers to significant positive or negative variations of volumes due to absorbtion or dessication of water in fine soils under natural or anthropic regime of moisture. These physical phenomena are worldwide spread and had important engineering consequences with associates cost of damages of several billion annually in all climate areas. In spite of the fact that these geotechnical properties are studied for more than eight decades, the particularities of these peculiar relations between water, mineral composition and geomechanical behavior are still unrevealed entirely. In Romania, swell/shrink soils are reported in all regions at different depths, but rarely related to geotechnical engineering accidents such as slope slides or road failures. This work presents some obvious relations between the hydrogeological structure, the presence of "large swell/shrink soils", their mineralogical composition and geomechanical properties and the ubiquitous landslides on Peri Carpathians Hills. Large infrastructure projects offer the opportunities to put into evidence the swelling properties of Upper Pliocene-Lower Pleistocene deposits, which supports the Holocene alluvial deposits of Argeş River. Analyzed samples allow us to define some basic correlations between plasticity index, colloidal fraction, dry density, swelling pressures or free swelling and mineralogical composition.
UNIVESITARIA SIMPRO 2021 May 27-28, 2021, Petrosani, Romania., 2021
Swelling and shrinking properties refers to significant positive or negative variations of volume... more Swelling and shrinking properties refers to significant positive or negative variations of volumes due to absorbtion or dessication of water in fine soils under natural or anthropic regime of moisture. These physical phenomena are worldwide spread and had important engineering consequences with associates cost of damages of several billion annually in all climate areas. In spite of the fact that these geotechnical properties are studied for more than eight decades, the particularities of these peculiar relations between water, mineral composition and geomechanical behavior are still unrevealed entirely. In Romania, swell/shrink soils are reported in all regions at different depths, but rarely related to geotechnical engineering accidents such as slope slides or road failures. This work presents some obvious relations between the hydrogeological structure, the presence of "large swell/shrink soils", their mineralogical composition and geomechanical properties and the ubiquitous landslides on Peri Carpathians Hills. Large infrastructure projects offer the opportunities to put into evidence the swelling properties of Upper Pliocene-Lower Pleistocene deposits, which supports the Holocene alluvial deposits of Argeş River. Analyzed samples allow us to define some basic correlations between plasticity index, colloidal fraction, dry density, swelling pressures or free swelling and mineralogical composition.
… , held 2-7 May, 2010 in …, 2010
Active fault systems may have significant influences in slow ground displacements during neotecto... more Active fault systems may have significant influences in slow ground displacements during neotectonic vertical or/and horizontal movements, or sudden ones, as a consequence of high magnitude earthquakes. In urban planning activities, besides a ...
SGEM International Multidisciplinary Scientific GeoConference EXPO Proceedings, 2020
Engineering Geology for Society and Territory - Volume 7, 2014
The Romanian engineering geology experience is a complex and intricate picture that has to be des... more The Romanian engineering geology experience is a complex and intricate picture that has to be described in terms of contributions to design and execution of engineering works realized during the last century and of individual or collective personalities which significantly contributed at the birth or development of this domain. The history described below refers to engineering geology roots which intertwine with hydrogeology and geophysics in Romania. Six decades of professional activity in the field of engineering geology represent a huge amount of work, effort and often sacrifice of many generations. The quality of their works is demonstrated by the fact that most part of their achievements is still in function and their successors spread all over the world and successfully apply the professional principles inherited. The complete itemization of all persons related to this activity is an impossible task, and authors apology for eventually overlook of persons or contributions and underline that there were mentioned only personalities that passed away.
Loose sands or very soft clays are sometimes hard to evaluate from geotechnical purposes with cla... more Loose sands or very soft clays are sometimes hard to evaluate from geotechnical purposes with classical methods like sampling and lab testing. The aim of the work was to estimate the applicability and reliability of some of the most popular relations derived from CPT tests in the case of marine sediments of Black Sea. The paper presents some comparisons between values of main geotechnical parameters derived by well known formulas from about 40m of CPT tests and laboratory tests executed on remolded samples of such soils, specific for shelf or wet areas. In the first instance a classical soil behavior chart was used in conjunction with grain size analyses, in order to define a more accurate soil profile. In the next step estimations of saturated or dry unit weights and friction angle of cohesionless submersed soils, base on well known relations was found in very good agreement with lab test values obtained from thin-walled tube samples. Finally, the evaluation of the state of stress puts in evidence that the investigated deposits are mainly underconsolidate or normal consolidate (OCR<2 and Ko<1) and at least one of three different classical relations for the estimation of relative densities, fits well with values of lab tests performed from the same depths.
15th International Multidisciplinary Scientific GeoConference SGEM2015, SCIENCE AND TECHNOLOGIES IN GEOLOGY, EXPLORATION AND MINING, 2015
Loose sands or very soft clays are sometimes hard to evaluate from geotechnical purposes with cla... more Loose sands or very soft clays are sometimes hard to evaluate from geotechnical purposes with classical methods like sampling and lab testing. The aim of the work was to estimate the applicability and reliability of some of the most popular relations derived from CPT tests in the case of marine sediments of Black Sea. The paper presents some comparisons between values of main geotechnical parameters derived by well known formulas from about 40m of CPT tests and laboratory tests executed on remolded samples of such soils, specific for shelf or wet areas. In the first instance a classical soil behavior chart was used in conjunction with grain size analyses, in order to define a more accurate soil profile. In the next step estimations of saturated or dry unit weights and friction angle of cohesionless submersed soils, base on well known relations was found in very good agreement with lab test values obtained from thin-walled tube samples. Finally, the evaluation of the state of stress puts in evidence that the investigated deposits are mainly underconsolidate or normal consolidate (OCR<2 and Ko<1) and at least one of three different classical relations for the estimation of relative densities, fits well with values of lab tests performed from the same depths.
Engineering Geology for Society and Territory - Volume 4, 2014
In the last decades the whole border of Black Sea had been tremendously damaged due to a number o... more In the last decades the whole border of Black Sea had been tremendously damaged due to a number of causes such as the construction of Iron Gates barrages and other dams on Danube effluents, or global sea level rising. The main objective of the project “Implementation of adequate infrastructure of natural risk prevention in most vulnerable areas. Reduction of coastal erosion” was to propose large scale measures in order to mitigate those effects (erosion and landslides). For this purpose, extensive and complex site investigations have been made by international research teams, among which geological, geotechnical and geophysical, on the whole Black Sea coast. The most interesting results were provided by offshore seismic investigations which depicted the presence of a fault network inside the major structural units, on which vertical tectonic movements can be a major cause of long term costal erosion and large scale landslides. The findings raise the problem of the choice of reference benchmark of all topographical, geological and hydrogeological monitoring systems of the whole South Dobrogea unit, knowing that the very large scale vertical movements are much more difficult to detect with usual survey programs.
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Papers by Stanciucu M Mihaela