SAND

Over the last century, large-scale water development of the upper Rio Grande in the U.S. and Mexico, and of the Rio Conchos in Mexico, has resulted in progressive channel narrowing of the lower Rio Grande in the Big Bend region. We used methods operating at multiple spatial and temporal scales to analyze the rate, magnitude, and processes responsible for channel narrowing. These methods included: hydrologic analysis of historic stream gage data, analysis of notes of measured discharges, historic oblique and aerial photograph analysis, and stratigraphic and dendrogeomorphic analysis of inset floodplain deposits. Our analyses indicate that frequent large floods between 1900 and the mid-1940s acted as a negative feedback mechanism and maintained a wide, sandy, multi-threaded river. Declines in mean and peak flow in the mid-1940s resulted in progressive channel narrowing. Channel narrowing has been temporarily interrupted by occasional large floods that widened the channel, however, channel narrowing has always resumed. After large floods in 1990 and 1991, the active channel width of the lower Rio Grande has narrowed by 36-52%. Narrowing has occurred by the vertical accretion of fine-grained deposits on top of sand and gravel bars, inset within natural levees. Channel narrowing by vertical accretion occurred simultaneously with a rapid invasion of non-native riparian vegetation (Tamarix spp., Arundo donax) which created a positive feedback and exacerbated the processes of channel narrowing and vertical accretion. In two floodplain trenches, we measured 2.75 and 3.5 m of vertical accretion between 1993 and 2008. In some localities, nearly 90% of bare, active channel bars were converted to vegetated floodplain during the same period. Upward shifts of stage-discharge relations occurred resulting in over-bank flooding at lower discharges, and continued vertical accretion despite a progressive reduction in stream flow. Thus, although the magnitude of the average annual flood was reduced between 40 and 50%, over-bank flooding continued. These changes reflect a shift in the geomorphic nature of the Rio Grande from a wide, laterally unstable, multi-thread river, to a laterally stable, single-thread channel with cohesive, vertical banks, and few active in-channel bars.

Both visible near-infrared (VNIR) and mid-infrared (MIR) spectroscopy have been claimed to better predict pesticide sorption in soils than other methods. We compared the performances of VNIR and MIR spectroscopy for predicting both organic carbon content (f OC ) and the sorption affinity (K d ) of diuron in 112 surface soils from South Australia. Separate calibration models were developed between VNIR and MIR spectra, and f OC and K d using partial least-squares (PLS) regression. MIR clearly outperformed VNIR for predictions of both f OC and K d in soils. Correlation (R 2 ) and accuracy (RPD) indices were 0.4 and 1.3 for the VNIR-PLS model versus 0.8 and 2.3 for the MIR-PLS model, respectively, for K d prediction. PLS loadings for sorption prediction were compared in terms of the soil information they contained. While VNIR loading did not include any direct spectral information regarding soil minerals, MIR loading included peaks associated with sand, clays, and carbonates. Perhaps by better predicting f OC and integrating the effects of OC as well as minerals, the MIR-PLS model provided a better prediction for diuron K d values in our calibration set.

Grain size analyses of three hilltop, primary eolian loess sequences in the Negev desert, southern Israel, show a bimodal grain-size distribution at 50-60 μm and 3-8 μm. Using analyses of mineralogy and OSL ages we demonstrate that the coarse mode is composed mostly of quartz grains and its relative magnitude increases regionally with time, suggesting an enhancement of a time-transgressive proximal dust source compared to a distal, Saharan fine-grain dust. The only proximal dust source for large amount of coarse silt quartz grains is the sands that advanced into Sinai and the Negev concurrently with the loess accretion during the late Pleistocene as a result of the exposure of the Mediterranean shelf. We therefore propose that the coarse silt quartz grains were formed through eolian abrasion within the margins of an advancing sand sea. This relationship between desert sand seas as a source for proximal coarse dust and desert margin loess deposits can be applicable to other worldwide deserts such as Northern Africa, China and Australia.

Problems of constructing a sediment budget for an inlet is often a challenge due to constraints on data collection, quality of data, and assumptions one is willing to consider. Existing literature does not provide a systematic foundation for equations considered and often engineers and geologists typically do not properly consider the mathematical constraints placed on the problem of sediment budget construction. The present technical note presents a simple methodology for assessing sediment budget, i.e. what is possible, and what is not possible via a matrix equation system and linear algebra. It is hoped that engineers and geologists will not impose unrealistic expectations on the sediment budget system via using such an approach. Some simple examples are given of both pitfalls and correct approaches to sediment budget development.

A number of motored auger holes have been drilled in 2002 and 2006 in four sand-clay deposits preserved in dissolution pockets within the Dinantian limestones of the watershed north of the Vesdre valley. These deposits of unknown age are currently classified as (Tertiary) SBL in the new geological map of Wallonia. We present detailed lithostratigraphic logs of the deposits and describe the results of sedimentological and mineralogical analyses. In particular, K-Ar dating of neoformed Mn oxides found at the base of one augerhole at Rechain yielded ages ranging from Cenomanian to Santonian, allowing us to place the Rechain and Andrimont deposits within the early Late Cretaceous. This is fully consistent with their topographic location very close beneath the trace of the pre-Cretaceous erosion surface and makes them the westernmost remains of the Hergenrath Member of the Late Cretaceous Aachen Formation. To the west, the Magnee deposit is more "typical SBL", probably correspo...

The Hermod sand of the Stine Segments, Siri Field, Danish North Sea, displays large permeability variations (1-600 mD). These permeability variations represent horizontal layering in the reservoir, largely formed by diagenetic processes. They have a significant impact on reservoir performance, because horizontal producers in fairly thin reservoirs ($30 m) are protected against bottom-water influx and can produce water-free for long periods of time. This paper presents the results of a detailed multidisciplinary study where the observed variation in permeability can be explained by two main diagenetic phases: silica, as opal cement and microquartz, and berthierine, a serpentine mineral that is closely related to chlorite. Opal/microquartz and berthierine cements dominate in separate parts of the reservoir bodies. Opal/ microquartz cemented sands have high permeability (typically 500-600 mD). Berthierine cement has a different growth pattern in the oil and water zones, resulting in intermediate permeability in the oil zone (typically 50-100 mD) and very low permeability in the water zone (typically 1-10 mD).

An integrated index to evaluate recreational sand beaches (IBVI) was designed using descriptive beach indicators (BI), beach user's perception (KI) and indicators of beach economic value (MI). This index was applied in five urban sandy beaches with similar physiographic features, but economically and socio-culturally different (Ensenada, Rosarito and Mazatlan in México; Copacabana in Brazil; and Oceanside in Southern California in USA). According to the IBVI evaluation, Oceanside was the best beach, all values rating high, followed by Copacabana with high BI and KI but low MI. Mazatlan was rated medium, although user's perception was high. Poorly developed beaches, such as Ensenada, were rated medium for BI, KI and low for MI. The IBVI value at Rosarito was rated mediumelow because both the BI and KI values were low. IBVI incorporates three visions for beach awards in one and can be useful to compare tourist sand beaches around the world.

A large number of collapse sinkholes have been developed in the period 1989-2004 in Famenin and Kabudar Ahang plains, Hamadan province, west of Iran. This paper discusses the Hamadan sinkhole conditions and their mechanism of formation. There is limestone bedrock at the base of a thick cohesive alluvial aquifer in the area. High purity of limestone, considerable porosity and existence of numerous joints and fractures favors high karstification of the limestone. Overexploitation of groundwater during the last decades created a significant drawdown in aquifer water table. Besides, deep wells penetrated to the limestone bedrock and evacuated fine-grained materials of overlain alluvial aquifer. Therefore, large cavities resulted from sand productive wells. Increasing effective stresses have mainly caused the formation of dropout sinkholes or cover-collapse sinkholes. The sinkholes of the plains roughly coincide with the maximum drawdown in the aquifer. Therefore, one of the main factors that has controlled the formation of sinkholes is the water table drawdown in the aquifers. Karstification of limestone bedrock and thick cohesive soil of overlain aquifer enhance the formation mechanism of sinkholes.

Full-scale load tests on 31 large footings situated on 13 different quartz-silica sand sites are used to develop a direct means for evaluating the vertical load-displacement and capacity response using tip resistances (q c) from cone penetration tests (CPT). Only large size foundations with footing widths 0.5 m  B  6 m were considered in order to avert difficulties found in scaling of small model test results. As no clear peak was observed, a reference "capacity" criterion is taken as the load corresponding to the s/B = 10% criterion, where s = footing displacement. It is found that the applied footing stress (q) vs. displacement (s/B) curves for all cases are unified when the foundation stress is normalized by the cone tip resistance.

The present study examined the antibiotic resistance of heterotrophic bacteria, which were isolated from the sand of the beach located in the National Park of the southern Baltic Sea coast. The bacteria demonstrated low levels of antibiotic resistance. These microorganisms were the most resistant to cefaclor and clindamycin and the most sensitive to clarithromycin, doxycycline, gentamycin and oxytetracycline. The majority of bacteria inhabiting the sand of the studied beach were resistant to only one antibiotic out of 18 tested antibiotics in this study. The bacteria inhabiting the middle part of the beach and the dune were more antibiotic resistant than bacteria isolated from the seawater and the shoreline-seawater contact zone. Generally, there was no significant difference in antibiotic resistance between bacteria isolated from the surface and the subsurface sand layers. The bacterial antibiotic resistance level depends on the chemical structure of antibiotics.

Decisions on landuse have become progressively more difficult in the last decades. The main reasons for this development lie in the increasing population combined with an increasing demand for new land and resources and in the growing consciousness for sustainable land and resource use. The steady reduction of valuable land leads to an increase of conflicts in land use decision-making processes since more interests are being affected and therefore more stakeholders with different land use interests and different valuation criteria are being involved in the decision-making process. In the course of such a decision process all identified criteria are weighted according to their relative importance. But assigning weights to the relevant criteria quickly becomes a difficult task when a greater number of criteria are being considered, especially with regard to land use decisions where decision makers expect some kind of mapped result it is therefore useful to use procedures that not only help to derive criteria weights but also accelerate the visualisation and mapping of land use assessment results. Both aspects can easily be facilitated in a GIS. This paper focuses the development of an ArcGIS VBA macro which enables the user to derive criteria weights with the analytical hierarchy process and which allows a mapping of the land use assessment results by a weighted summation of GIS raster data sets. A dynamic link library for the calculation of the eigenvalues and eigenvectors of a square matrix is provided. r

The concentration rare earth elements and Yttrium (REE + Y) were determined in coral sands from Kavaratti Island, Arabian Sea, India. Chondrite-normalized REE + Y patterns show: (1) high REE concentration particularly light REE (LREE) enrichment; (2) consistent negative Ce anomaly; (3) nearly chondritic Y/Ho ratios. All these features are consistent with the geochemistry of well oxygenated seawater with significant terrestrial contribution. The seawater composition of Nd/Yb ratio inferred from the coral record point to the dominance of LREE more than the heavy REE (HREE). The high terrestrial input rich in LREE and property of adsorption/scavenging processes of LREE than that of HREE may be the cause. Terrigenous contributions were detected on the basis of cooccurring trace element concentrations (Sc, Hf and Th) and Y/Ho ratio. Except for La, the REE distribution coefficients, KD(REE)s, are between 100 and 300. KDs are high comparing to the other elements in biogenic calcite which is attributed to detrital contamination during elemental incorporation. This study may not reflect original seawater chemistry but it can be a good proxy to indicate proximity of corals to terrigenous input sources.

In arid and semi-arid regions, water is a major limited factor to vegetation and environment. To study the influence of membranes on water retention, three homogeneous sand columns with membranes were installed. Keep the height of free water at Scm above the soil surface of those columns for 3 hours. Experiments results showed that membranes have strong influence on water retention in saturated sand columns. The membranes could slower water movements through the columns and reduce water dynamic parameters such as hydraulic conductivity. So it has an important role in water retention in sand soils, especially in arid and semi-arid regions.

The zoanthid family Neozoanthidae (Anthozoa: Hexacorallia: Zoantharia) was described in 1973 from Madagascar as a monogeneric and monotypic taxon, and never reported again in literature. In 2008-2010, numerous zoanthid specimens fitting the morphological description of Neozoanthus were collected in the Ryukyu Islands, Okinawa, Japan, and the Great Barrier Reef (GBR), Australia. Utilizing these specimens, this study re-examines the phylogenetic position of Neozoanthidae and analyzes the evolutionary history of sand incrustation in zoanthids through phylogenetic and ancestral state reconstruction analyses. Specimens were colonial, partially incrusted with large, irregular sand and debris, zooxanthellate, and found from the intertidal zone to depths of approximately 30 m. Phylogenetic results utilizing mitochondrial 16S ribosomal DNA and cytochrome oxidase subunit I sequences show the presence of two Neozoanthus species groups, one each from Japan and the GBR. Unexpectedly, the molecular results also show Neozoanthus to be very closely related to the genus Isaurus, which as a member of the family Zoanthidae, is not sand incrusted. These results suggest that during evolution zoanthids can acquire and lose the ability to incrust sand with relative rapidity. Communicated by C. Riginos.

Between Point Grenville, Washington, and Point Conception, California (1500 km distance) 21 dune fields record longshore transport in 20 littoral cells during the late Holocene. The direction of predominant littoral transport is established by relative positions of dune fields (north, central, or south) in 17 representative littoral cells. Dune field position is north of cell midpoints in northernmost Oregon and Washington, but is south of cell midpoints in southern Oregon and California. Downdrift sand trapping occurs at significant changes in shoreline angle and/or at bounding headlands that project at least 2.5 km seaward from the general coastal trend. Sand bypassing occurs around small headlands of less than 0.5 km in projection distance. A northward shift of the winter low-pressure center in the northeast Pacific Ocean is modeled from 11 ka to 0 ka. Nearshore current forcing in southern Oregon and northern California switched from northward in earliest Holocene time to southward in late Holocene time. The late Holocene (5-0 ka) is generally characterized by net northward littoral drift in northernmost Oregon and Washington and by net southward littoral drift in southernmost Oregon and California. A regional divergence of net transport direction in central Oregon, i.e. no net drift, is consistent with modeled wind and wave forcing at the present time (0 ka).

Determinations of soil moisture and sediment availability in arid regions are important indicators of local climate variability and the potential for future dust storm events. Data from the Advanced Spaceborne Thermal Emission and Reflection (ASTER) radiometer were used to derive the relationships among potential soil erosion, soil moisture, and thermal inertia (TI) at the spatial scale of aeolian landforms for the White Sands Dune Field between May 2000 and March 2008. Land surface apparent thermal inertia (ATI) data were used to derive an approximation of actual TI in order to estimate the wind threshold velocity ratio (WTR). The WTR is a ratio of the wind velocity thresholds at which soil erosion occurs for wet soil versus dry soil. The ASTER-derived soil moisture retrievals and the changes through time at White Sands were interpreted to be driven primarily by precipitation, but the presence of a perched groundwater table may also influence certain areas. The sediment availability of dunes, active playa surfaces and the margin of the alluvial fans to the west were determined to be consistently higher than the surrounding area. The sediment availability can be primarily explained by precipitation events and the number of dry days prior to the data acquisition. Other factors such as vegetation and the amount of surface crusting may also influence soil mobility, but these were not measured in the field. This approach showed the highest modeled sediment availability values just days prior to the largest dust emission event at White Sands in decades. Such an approach could be extended to a global monitoring technique for arid land systems that are prone to dust storms and for other regional land surface studies in the Sahara.

In the present study, the effects of multiple-footing configurations in sand on bearing capacity were investigated using field plate load tests and finite element analyses. Both strip and spread footings were considered in the finite element analyses. In each case, different footing distances were applied for the purposes of comparison among all of the results. From these results, it was observed that the load responses of multiple footings are similar to those of the single footing at distances greater than three times the footing width. Design equation and correlation parameters, necessary for quantifying the values of the bearing capacity ratio for the different multiple-footing configuration, were derived. Experimental test results from the literature were selected and used in verifying the proposed method.

Forward seismic models of two 'seismic scale' outcrops of different style channel systems have been made to investigate their seismic signature. These two outcrops illustrate the geometric end members of channel stacking architecture in response to low-and highaccommodation space. The Eocene Nohut Tepe channel system of the Elazig˘Basin in eastern Turkey was deposited in an area of high accommodation resulting in an aggradational geometrical offset stacking of channels up against a slope. The Eocene Ainsa II Channel system of the Tremp-Pamplona Basin in the Spanish Pyrenees was deposited in an area of low accommodation resulting in a tabular, compound sheet geometry, with amalgamated channel bodies separated by clay drapes.

The different classification of particle-size fractions used in Australia compared with other countries presents a problem for the immediate adoption of the exotic pedotransfer functions. Australia adopted the international system which defined silt as particles with diameters in the range 2-20 µm, while the USDA/ FAO define it as 2-50 µm. We present empirical equations to convert between the two systems. The USDA/ FAO textural classes were also plotted in the International system's coordinate. The USDA/FAO classes in the International system had a 'boomerang' shape and only occupy 60% of the triangle. Particle-size data showed that the data are evenly distributed in the USDA/FAO triangle, while most data are concentrated in the boomerang in the International system. We therefore suggest that it would seem wise for most countries to consider adopting the particle-size limits and texture classes of the USDA/FAO system.

It is well-known that specimen-preparation method and the resulting sand fabric significantly affect sand behavior. In many cases, the fabric and behavior of reconstituted sand samples do not represent those of in-situ deposits. Therefore, understanding the influence of specimen preparation and sand fabric on its behavior, particularly at the critical state, is important for relating the behavior of laboratory reconstituted specimens to in-situ soil response. In this study, the effect of sand fabric and specimen-preparation method on the shearing behavior of three sands is studied using ring-shear tests. Ring-shear tests are used to reach large shear displacements and determine critical states, particularly for dense sand specimens. Moist tamping and air pluviation are used to prepare the specimens. The results indicate that the shearing behavior of sand in ring-shear tests is not only affected by the specimen-preparation method (i.e., sand fabric), but also by particle damage and compressibility. However, these mechanisms do not affect the critical states at which particle rearrangement and damage are complete and the initial sand fabric is completely erased.

The undrained response of cohesive soils is of paramount importance in geomechanics and it has been modelled extensively for the last 50 years. In comparison, drained behaviour of clays has received only modest attention. Drained and undrained behaviour is significantly affected by past consolidation stress history. This paper evaluates the capabilities of the MIT-S1 effective stress model, described in a companion paper, for predicting the anisotropic stress-strain-strength behaviour of clays. The paper illustrates the selection of model parameters for Lower Cromer Till, using data from standard types of laboratory tests. Comparison of model simulations with measured response for Lower Cromer Till and Boston Blue Clay illustrate model capabilities. The work focuses initially on comparisons of model predictions with measurements from undrained triaxial and plane strain tests on initially K 0 -consolidated specimens. Comparisons with measured data from undrained shear tests performed in different modes of shearing for LCT and BBC show that the model: (a) gives excellent predictions of maximum shear stress conditions and accurately describes the non-linear shear stress-strain behaviour; (b) accurately describes the anisotropic shear stress-strain-strength conditions for different consolidation stress histories; and (c) gives realistic description of mobilized friction angles, especially at large OCR's. The paper then focuses on the effects of consolidation stress history for isotropically consolidated specimens of resedimented Lower Cromer Till and Boston Blue Clay. Finally, the paper compares model predictions for drained shear tests on K 0 and isotropically consolidated specimens with overconsolidation ratios, OCR410; used to evaluate particular aspects of the critical state framework of soil behaviour. Overall, the model gives excellent predictions of the effect of initial anisotropy and overconsolidation stress history on the shear stress-strain and volumetric behaviour of clays.

Laboratory experiments on undisturbed specimens of a large number of soft clay deposits, as well as previous measurements on clays and granular soils, were used to examine and explain the magnitude and behavior of the coefficient of earth pressure at rest, K0: (i) after sedimentation – primary consolidation, (ii) during secondary-compression aging, (iii) after active or passive preshearing away from the laterally constrained condition, (iv) during a decrease in effective vertical stress, and (v) during an increase in effective vertical stress in the recompression or compression range, in terms of [Formula: see text], the slope of the effective horizontal [Formula: see text] versus effective vertical[Formula: see text] stress path. The behavior of K0 is explained using the concept of mobilized angle of friction in laterally constrained deformation condition. The Jaky equation provides, in terms of the angle of internal friction, a good estimate of K0 of sedimented, normally consolida...

Elastic full waveform inversion of seismic reflection data represents a data-driven form of analysis leading to quantification of sub-surface parameters in depth. In previous studies attention has been given to P-wave data recorded in the marine environment, using either acoustic or elastic inversion schemes. In this paper we exploit both P-waves and mode-converted S-waves in the marine environment in the inversion for both P- and S-wave velocities by using wide-angle, multi-component, ocean-bottom cable seismic data. An elastic waveform inversion scheme operating in the time domain was used, allowing accurate modelling of the full wavefield, including the elastic amplitude variation with offset response of reflected arrivals and mode-converted events. A series of one- and two-dimensional synthetic examples are presented, demonstrating the ability to invert for and thereby to quantify both P- and S-wave velocities for different velocity models. In particular, for more realistic low velocity models, including a typically soft seabed, an effective strategy for inversion is proposed to exploit both P- and mode-converted PS-waves. Whilst P-wave events are exploited for inversion for P-wave velocity, examples show the contribution of both P- and PS-waves to the successful recovery of S-wave velocity.

Quarry dust is a by-product from the granite crushing process in quarrying activities. This paper presents the findings from experimental work undertaken to evaluate the suitability of quarry dust as a partial substitute for sand in high-strength concrete (HSC) containing rice husk ash (RHA). Two grades of HSC mixes, to achieve 60 MPa and 70 MPa at 28 days, were designed with and without the incorporation of RHA. Quarry dust was then used in the mixes containing RHA as a partial substitute for sand, in quantities ranging from 10 % to 40 %. The slump of the fresh concrete and the compressive strength development were monitored up to 28 days. Based on the results obtained, the mixes containing 20 % quarry dust were chosen as the optimum mix design for both grades of concrete, which would then undergo further evaluation of their strength and mechanical properties up to one year. The results obtained in the next stage suggest that even though the use of quarry dust as a partial substitute for sand results in some minor negative effects in the compressive strength and other mechanical properties of concrete, these outcomes can easily be compensated by a good mix design and by the incorporation of RHA. The findings of the research assert that quarry dust can be used as a viable replacement material to sand to produce high-strength RHA concrete.

A previous review by the first author of the literature on the effects of seawalls on the beach is extended to cover the period 1988 to the present. The review synthesizes knowledge on beach profile change, longshore sand transport, and scour in the vicinity of seawalls. Remarkable progress has been made since 1988. with new phenomena and observations reported. such as on longshore transport processes at walls. Some previous results and conclusions of the 1988 review have been cast into doubt, with example now results being that (1) wave reflection at walls may not be a significant contributor to profile change, and 121 scour at seawalls in the field may be more a product of longshore transport and return of overtoppmg water than a result of direct cross-shore wave action. The validity or usefulness of small-scale physical model tests is questioned. Conclusions and recommendations for future work are given. This paper is the first of a companion set of papers that investigate the effects of seawalls on the beach. The second paper presents a numerical model of cross-shore transport and beach profile change at seawalls that includes wave reflection, and it compares predictions to measurements made at the SUPERTANK project and to recent results found in the literat ure on scour at walls.

This paper aims at developing analytical solutions for estimating the ultimate bearing capacity of geogrid reinforced soil foundations (RSF) for both sand and silty clay soils. Failure mechanisms for reinforced soil foundations are proposed based on the literature review and the results of experimental study on model footing tests conducted by the authors. New bearing capacity formulas that incorporate the contribution of reinforcements to the increase in bearing capacity are then developed for both reinforced sand and silty clay soil foundations based on the proposed failure mechanisms. The predicted bearing capacity values are compared with the results of laboratory model tests on reinforced sand and silty clay soil. The proposed analytical solutions were also verified by the results of large-scale model tests conducted by the authors for reinforced silty clay and the data reported in the literature. The predicted bearing capacity values from analytical solutions are in good agreement with the test results.

The aim of this study is to define and characterize water bearing geological formation and to test the possibility of using geophysical techniques to determine the hydrogeological parameters in three areas in the Vientiane basin, Laos. The investigated areas are part of the Khorat Plateau where halite is naturally occurring at depths as shallow as 50 m in the Thangon Formation. Magnetic Resonance Sounding (MRS) has been used in combination with Vertical Electrical Sounding (VES) in different geological environments. In total, 46 sites have been investigated and the MRS and VES recognized the stratigraphic unit N 2 Q 1-3 , consisting of alluvial unconsolidated sediments, as the main water bearing unit. The aquifer thickness varies usually between 10 and 40 m and the depth to the main aquifer range from 5 to 15 m. The free water content is here up to 30%, and the decay times vary between 100 and 400 ms, suggesting a mean pore size equivalent to fine sand to gravel. The resistivity is highly variable, but usually around 10-1500 Ω-m, except for some sites in areas 1 and 2, where the aquifer is of low resistivity, probably related to salt water. Hydraulic and storage-related parameters such as transmissivity, hydraulic column, have been estimated from the MRS. The MRS together with VES has been shown to be a useful and important tool for identifying and distinguishing freshwater from possible salt-affected water as well as the salt-related clay layer of the Thangon Formation. This clay layer is characterized by very low free water content and a resistivity lower than 5 Ω-m and can be found in all 3 areas at depths from 15 to 50 m.

Decisions on landuse have become progressively more difficult in the last decades. The main reasons for this development lie in the increasing population combined with an increasing demand for new land and resources and in the growing consciousness for sustainable land and resource use. The steady reduction of valuable land leads to an increase of conflicts in land use decision-making processes since more interests are being affected and therefore more stakeholders with different land use interests and different valuation criteria are being involved in the decision-making process. In the course of such a decision process all identified criteria are weighted according to their relative importance. But assigning weights to the relevant criteria quickly becomes a difficult task when a greater number of criteria are being considered, especially with regard to land use decisions where decision makers expect some kind of mapped result it is therefore useful to use procedures that not only help to derive criteria weights but also accelerate the visualisation and mapping of land use assessment results. Both aspects can easily be facilitated in a GIS. This paper focuses the development of an ArcGIS VBA macro which enables the user to derive criteria weights with the analytical hierarchy process and which allows a mapping of the land use assessment results by a weighted summation of GIS raster data sets. A dynamic link library for the calculation of the eigenvalues and eigenvectors of a square matrix is provided. r

Model sheet pile wall tests were conducted in sand to investigate the effect of surcharge strip loads on wall behavior. Bending-moment graphs are presented for several values of strip load intensity and distance from the wall. Measured bending moments are compared to ...

The Kalahari sand sheet, with a 2.5-million ha area, is probably the largest continuous surface of sand in the world. The Kalahari Transect (KT) is one of a set of IGBP ''megatransects'' identified for global change studies and provides an ideal setting to investigate changes in ecosystem dynamics, vegetation composition and structure, and carbon or nutrient cycles along a spatial precipitation gradient without confounding soil effects. Soil physical properties remain poorly characterized along the KT. The present work provides a review of previous studies on the Kalahari soils combined with new results from recent analyses of physical (mostly hydraulic) and biogeochemical properties of the soil. In summary, the Kalahari soil is acidic, dominated by sand and nutrient poor. Nutrient contents, soil textures and soil hydraulic properties differ under and between canopies. Roots are concentrated in the top 80 cm of the soil, with grass roots more abundant and dominant close to the surface. Moreover, the distribution of tree roots does not exhibit a clear dominance over grasses at deeper soil layers. This review provides important baseline information for this system, as well as insights as to how biochemical processes vary along a rainfall gradient. r

Sur les hautes terres malgaches, le bassin d'Antsirabe, d'origine tectonique, présente un socle cristallin faillé, bordé à l'ouest par des édifices volcaniques récents (Vakinankaratra). Le bassin sédimentaire présente deux surfaces planes, étagées et légèrement inclinées vers le sud, qui ont été considérées jusqu'alors comme témoignant chacune d'un remplissage lacustre. Les séries stratigraphiques reconnues présentent, sur le socle ou ses altérites, deux corps sédimentaires remarquables. A la base, sur une dizaine de mètres d'épaisseur, une série fluvio-palustre de plaine d'inondation, où sables, limons et graviers alternent avec des niveaux tourbeux décimétriques, au nombre maximum reconnu de sept sur une même verticale. Au-dessus, une couverture de cinérites, fine au sud-est et plus grossière au nord-ouest, atteint généralement vingt mètres d'épaisseur. Les datations 14 C obtenues placent les alluvions fluviopalustres entre 35 000 BP et 14 400 BP. La série volcanique explosive majeure est donc plus récente que 14 400 BP. Elle aurait duré 6 000 ans. La vitesse moyenne de dissection de ces matériaux tendres peut être relativement bien cernée. Le comblement du bassin d'Antsirabe n'est donc pas d'origine lacustre, de tels sédiments n'ayant été reconnus que ponctuellement à la base de la série, le long de la faille du Mandray. Le remplissage du bassin d'Antsirabe constitue de ce fait une archive sédimentaire remarquable correspondant aux stades isotopiques 2 et 3 d'une plus grande fiabilité que les sédiments de lacs de cratère proches.

This work is based on the knowledge of the consolidation of silica sand with an alkaline solution in order to determine the mechanisms that occur during the drying of sand and various alkaline solution mixtures. The investigations concern effects of sand distribution size, dilution of sodium silicate solutions and drying temperature of the mixtures on consolidation behaviour. The thermal analysis

Current methods to improve the engineering properties of sands are diverse with respect to methodology, treatment uniformity, cost, environmental impact, site accessibility requirements, etc. All of these methods have benefits and drawbacks, and there continues to be a need to explore new possibilities of soil improvement, particularly as suitable land for development becomes more scarce. This paper presents the results of a study in which natural microbial biological processes were used to engineer a cemented soil matrix within initially loose, collapsible sand. Microbially induced calcite precipitation ͑MICP͒ was achieved using the microorganism Bacillus pasteurii, an aerobic bacterium pervasive in natural soil deposits. The microbes were introduced to the sand specimens in a liquid growth medium amended with urea and a dissolved calcium source. Subsequent cementation treatments were passed through the specimen to increase the cementation level of the sand particle matrix. The results of both MICP-and gypsum-cemented specimens were assessed nondestructively by measuring the shear wave velocity with bender elements. A series of isotropically consolidated undrained compression ͑CIUC͒ triaxial tests indicate that the MICP-treated specimens exhibit a noncollapse strain softening shear behavior, with a higher initial shear stiffness and ultimate shear capacity than untreated loose specimens. This behavior is similar to that of the gypsum-cemented specimens, which represent typical cemented sand behavior. SEM microscopy verified formation of a cemented sand matrix with a concentration of precipitated calcite forming bonds at particle-particle contacts. X-ray compositional mapping confirmed that the observed cement bonds were comprised of calcite.