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This study investigates clayey soil from a road project situated in the district of Lodhran, Punjab, Pakistan. The subgrade prepared with the soil distorted due to heaving after a certain period of its construction. First, laboratory tests were conducted to explore the reason for this problem, examining the fundamental engineering properties of soil. The test results show that the soil acts as a soft material when water content reaches 30%, significantly reducing its strength. The soft soil is generally considered unsuitable for civil work due to its poor performance behaviour. So, the performance of clayey soil was examined in the study at its soft state by coupling it with stronger materials, such as polyethylene polymeric reinforcement and sand, developing laboratory-scale foundation models. Based on the model studies, the study proposes a sustainable polyethylene–sand–soft soil model, which shows 155 and 56% higher ultimate bearing capacity (BC) than soft soil and sand-reinforced soft soil foundations. The changes in BC occur due to the reinforcement action of the polyethylene reinforcement, which is associated with its tensile membrane action effects and interlock bonding at the soil-reinforcement interface. Practically, the study can reduce the dependency of industry practitioners on sand materials. Using polyethylene in civil work is viable for environmental sustainability. [ABSTRACT FROM AUTHOR]

Clay soils are rock‐decomposed materials comprised of both clay‐ and non‐clay‐like minerals. Clays' physiochemical and mineralogical composition determines their applicability use in cosmetics. Because of their high bioburden, they must be effectively characterized before being incorporated into cosmetics. The scope of the current study was to characterize two different samples of red and white clays for their physical, chemical and biological properties; mined from Durban, South Africa. Characterization was performed using techniques like X‐ray fluorescence, X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope, hydrogen potential, soil colour, oil absorption, swelling capacity, texture, bulk density, plastic and apparent viscosity, sun protection factor and microbiological analysis. [ABSTRACT FROM AUTHOR]

Electro-osmotic drainage technology is especially suitable for low-permeability clay soil. The electrode–clay interface is believed to play a crucial role in electro-osmosis. Previous documents have highlighted the importance of the electrochemical processes at the electrode–clay interface, but few studies exist with respect to the influencing mechanisms. Therefore, the influencing mechanisms of the electrochemical processes on the electrode–clay interface have been thoroughly studied herein, both theoretically and experimentally. An interfacial resistance model in the electro-osmotic system is proposed based on the interfacial kinetic reactions of metal electrodes and graphite electrodes according to electrochemical theory. The reliability of the proposed model is demonstrated by chamber tests. The proposed model states that the most critical factor influencing interfacial resistance is the current density on the electrode surface. Other crucial influencing factors for interfacial resistance include the electrode material, surface status, pH of the pore solution, soil void ratio, conductive properties and adsorption properties. [ABSTRACT FROM AUTHOR]

Montmorillonite (Mnt), belonging to the smectite group and representing a 2:1-type clay mineral with good cation-exchange and swelling capacities, is a common clay component of soils. It was observed that some Mnt preparations exhibit peroxidase-like (P-L) activity using N,N-diethyl-p-phenylenediamine sulfate salt as a substrate. Both native (non-swelling) and swelling Mnt exhibited similar P-L activity. Modification of Mnt with copper and iron influenced both P-L activity and phenol polymerization. Both free and textile-bound Cu-Mnt (Sigma-Aldrich) enabled phenol removal. Soil Mnt P-L activity is probably involved in lignin breakdown and decontamination of soils polluted with phenol-containing molecules. [ABSTRACT FROM AUTHOR]

The paper investigates the effect of hydrated lime on shear strength properties and behaviour of London clay, triaxial. Unconsolidated undrained tests were performed to identify the effect of lime dosage, compaction water content and curing time on the shear strength and stress–strain behaviour of the treated soil. The mineralogical and physicochemical transformations occurring during the curing of the soil were also monitored. The results showed that strength gain was strongly influenced by lime content and the curing period, whereas compaction water content was less influential. It was found that the strength evolution is likely to continue over long periods of time and result in very considerable strength gains on the hardening of pozzolanic reaction products. It was also shown that adequate early strength gains can be obtained with reduced material consumption, thus further increasing the sustainability of the treatment processes. The paper also highlighted the importance for engineering design of considering the brittle stress–strain response of the lime-treated soil, and the benefit of using lower amounts of lime to alleviate this undesirable effect. The implications of various aspects of soil brittleness in different situations merit further attention and should be explored by way of modelling in future work. [ABSTRACT FROM AUTHOR]

Desiccation cracking in clayey soils is a complex phenomenon investigated by researchers over many decades. Understanding and mitigating this issue will have a significant influence on the performance of raw earth construction materials and geotechnical engineering. In the current study, the digital image correlation technique was used to provide a thorough insight about the shrinkage anisotropy and the cracking mechanisms during drying. A series of free shrinkage tests were performed on an initially saturated slurries in order to assess the effects of the intrinsic characteristics of the material, the surface tension, the sample thickness and the geometric boundary conditions on the crack initiation and propagation in clays. The results show that increasing sample thickness prevents cracks formation in a non-swelling clay and delays it in a swelling clay. A vertical uplift was observed in the swelling clay due to a concave bending of the material during the desiccation shrinkage. An important anisotropy in the vertical shrinkage was observed compared to the horizontal shrinkage. The geometric boundary conditions indirectly influence the internal drying stress that becomes anisotropic. The intrinsic characteristics have a greater effect on the shrinkage behavior of the material than the hygrothermal and geometric boundary conditions. [ABSTRACT FROM AUTHOR]

Understanding of desiccation-induced cracking in soil has improved over the last 20–30 years through experimental studies, but progress in predictive modelling of desiccation cracking has been limited. The heterogeneous structure of soils and the multi-physics nature of the phenomenon, involving emergence and propagation of discontinuities, make the mathematical description and analysis a challenging task. The authors present a non-local hydro-mechanical model for soil desiccation cracking capable of predicting crack initiation and growth. The model is based on peridynamics (PD) theory. Attempts to model soil desiccation cracking by PD are limited to a purely mechanical description of the process that involves calibration of the parameters. In contrast, the model presented in this paper describes soil desiccation cracking as a hydro-mechanical problem, where moisture flow and deformation are coupled. This allows for investigating and explaining the mechanisms controlling the initiation and propagation of discontinuities. The model is applied and tested against two sets of experimental data to explain the typical features of drying-induced cracking of clays. The validations use experimental parameters (Young's modulus, water retention characteristics) and avoid calibrations to test the accuracy of the model. The correlations between the shrinkage of soil clay, changes in displacement fields and crack growth are demonstrated. Crack initiation, propagation and ultimate crack patterns simulated by the model are found to be in very good agreement with experimental observations. The results show that the model can capture realistically key hydraulic, mechanical and geometry effects on clay desiccation cracking. [ABSTRACT FROM AUTHOR]

Desiccation cracking in clay soils is a combined mechanical and hydraulic problem and such soils can be improved by various methods including reinforcement with fibres. The relationships between tensile strength, cracking resistance and water-retention properties of fibre-reinforced fine-grained soils lack coverage in the literature to date. In this study, these three properties are evaluated and connected by way of a series of tensile strength and desiccation cracking tests on fibre-reinforced London clay. The results confirm that increased fibre addition delays the occurrence of peak stress and changes failure behaviour from brittle to ductile. The tensile strength increment gets higher as water content decreases, and reaches a maximum value of 460 kPa when the water content is 12%. The crack intensity factor reduces from 7.20% to 0.89% when 12 mm long fibre is used at a ratio of 0.9%. Fibre reinforcement also changes the crack development pattern by reducing the size of large cracks and increasing the proportion of small individual cracks. However, the presence of fibres was not observed to change the water-retention properties of the soil, indicating that the tensile improvement comes from the pull-out resistance of the fibres rather than suction changes. [ABSTRACT FROM AUTHOR]

This research evaluates the changes brought about by the addition of asphalt emulsion and steel filings in clayey soils for subgrade in urban pavements. For this study, different dosages of each additive were established, being 1%, 2%, 4%, 8%, and 15% for the steel filings and 3%, 6%, 9%, 13%, and 18% for the asphalt emulsion, obtaining favorable results in the subgrade in accordance with the CE.010 Urban Pavement standard. With the steel filings the CBR (California Bearing Ratio) had a linear increase whose maximum value was reached with the dosage of 15% increasing the CBR considerably by 189.47% above the CBR of the natural soil; on the other hand, with the asphalt emulsion a maximum increase in CBR was obtained with the dosage of 13% obtaining an increase of 236.84% and after that a decrease is observed with the addition of 18% of asphalt emulsion. [ABSTRACT FROM AUTHOR]

• A unified gross traction algorithm is proposed for braked, towed, and powered wheels on clay. • The model is developed using the Database Records for Off-road Vehicle Environments. • The algorithm employs the ratio of average contact pressure to cone index. • The new equation can be implemented in off-road mobility models. A characteristic curve is presented for predicting gross traction of a wheel over a range of powered, towed, and braked modes on clay soils for slip ranging from positive 100% powered slip to negative 100% skid slip. The characteristic curve is a unified approach that relates the ratio of the contact pressure of the wheel to soil strength and predicts the gross traction coefficient over a continuous range of slip. The unified equation is defined by five inflection points: maximum/minimum traction, traction at zero slip, max change in traction with slip, and a shape factor coefficient. The inflection points aim to simplify the calibration of gross traction, slip, soil strength, and contact pressure by using functions adaptable to machine learning. The unified equation is comparable to historic traction equations but is unique in its ability to predict asymmetric braking and powered gross traction. The unified equation is supported and substantiated via error analysis by utilizing the Database Records for Off-road Vehicle Environments (DROVE) – a database constructed around the archived laboratory and field tests for wheels and tracks operating on different soils. The accuracy of the proposed model is assessed and compared to other conventional equations such as the Brixius equation and Maclaurin's extension of the Pacejka equation for off-road traction. [ABSTRACT FROM AUTHOR]

Unconfined compressive strength ( S u ) is one of the soil engineering parameters used in geotechnical designs. Due to the temperature changes caused by some human activities, it is important to study the changes in S u at different temperatures. On the other hand, due to the differences in the mineralogical composition of clay soils, it is important to study this subject in different clays. For this purpose, kaolin, illite and montmorillonite clays with a liquid limit (LL) of 47, 80 and 119, were tested in a temperature-controlled cell in temperature range of 20 to 60 ∘ C. Temperature was applied in undrained conditions and the results showed that the pore water pressure was a function of temperature and by heating, it increased in the samples. For specific temperature pore water pressure generated in montmorillonite was higher than Illite and kaolin. In all three types of clay, the S u decreased linearly with increasing temperature. The reduction of S u in kaolin was more than illite and in illite was more than montmorillonite. For all three samples, with increasing temperature, the modulus of elasticity (E) decreased non linearly. Increasing the temperature reduced strength and the stiffness of the clay samples.. The results of unconfined compressive tests at different temperatures were simulated using hypoplastic model. Impact of temperature was replicated by the model. [ABSTRACT FROM AUTHOR]

The goal of this paper is the characterisation of seven clays of the province of Alicante (SE Spain) and their possible use to improve the fertility, water absorption and contaminant-retaining capacity of degraded soils. Three soils affected by the dumping of construction debris were also studied to diagnose the problems and possible recovery strategies. Several physicochemical properties were measured, such as the water holding capacity, soil organic matter, lime, pH, EC and CEC. A high correlationship between mineralogical and elemental composition was obtained. Illite was present in all clays and soils. Some of the samples also contained kaolinite and significant amounts of lime. The CEC, as expected, was more closely related to the organic matter content. Soil organic matter was detected in the second derivative of the FTIR spectra by the signals of the CH2 groups at 2850 and 2919. This way, the FTIR spectrum for the soils of the area would make it possible to estimate both the organic matter content and the CEC. Despite their origin, soils did not show heavy metal pollution; however, salinisation risk seemed to be the most probable cause of degradation. According to the organic matter, lime and illite content, two clays were selected as the most suitable for soil degradation recovery. Furthermore, organic matter additions may help to improve the self-depurative ability of the soil. [ABSTRACT FROM AUTHOR]

In the geotechnical community, the macroelement approach nowadays is largely considered to be a successful theoretical tool for solving soil–structure interaction problems. This approach is based on the definition of a generalised constitutive law putting in relation a small number of suitably defined generalised stress/strain variables. The macroelement formulations proposed in the literature take into consideration either drained or undrained cases, but disregard the hydro-mechanical coupling. In this paper, the authors intend to generalise the theory by introducing a new formulation for shallow foundations overpassing this limitation and capable of accounting for the influence of loading rate on the system response. To conceive and to calibrate the model, the authors numerically analysed the case of a shallow foundation positioned on a normally consolidated clayey soil stratum whose mechanical behaviour is reproduced by means of the modified Cam Clay model. Finally, the approach is discussed critically from the perspective of its use as a design tool according to approaches based on the ultimate limit state and displacement. [ABSTRACT FROM AUTHOR]

This paper presents the results of centrifuge model tests and three-dimensional large-deformation finite-element analysis on axial pipe–soil sliding behaviour of partially embedded subsea pipelines. A three-dimensional re-meshing and interpolation technique with small strain approach was adopted using the Abaqus mesh-to-mesh solution mapping feature with the Cam Clay model. The parameters studied include soil properties, interface friction coefficient, embedment depth and post-lay reduction in vertical load. Embedment depth and post-lay load reduction were found to exercise the strongest influence on the post-consolidation and sliding behaviour. Empirical relationships correlating centrifuge experiments and numerical modelling are proposed for the embedment enhancement factor in terms of the embedment and vertical load ratios, under conditions of very slow sliding, corresponding to the drained condition. For very fast sliding, corresponding to effectively undrained conditions, similar relationships involving embedment and vertical load ratios and interface friction coefficients are also proposed. Finally, the variation of embedment enhancement factor with sliding velocity is expressed in terms of a relative enhancement index, Ψ, which can be adequately described by hyperbolic relationships for the complete range of consolidation history. These relationships provide a basis for the evaluation of the embedment enhancement factor corresponding to an arbitrary sliding velocity, which can be used in routine analysis and design of as-laid underwater pipelines in soft clayey soils. [ABSTRACT FROM AUTHOR]

A relationship between elastic anisotropy, as typically observed in clayey soils subjected to shear wave propagation tests, and plastic anisotropy, detected at yielding and leading to rotated yield loci, is proposed. Such a relationship is expected because both elastic and plastic anisotropies can be ascribed to the same directional ingredients that characterise the fabric of the soil at the microscale. The relationship takes the form of an analytical relation between an elastic and a plastic fabric tensor, the former entering a hyperelasticity theory while the latter is the rotational hardening variable of a clay plasticity theory. The elastic anisotropy can be measured experimentally by wave propagation along orthogonal planes, identifying the ratio of the corresponding elastic shear moduli while a sample is compressed at fixed stress ratio, and paired with plastic anisotropy obtained by the integration of its plastic fabric tensor evolution equation during the foregoing compression. Such experiments were available and used to calibrate and validate the proposed elastic–plastic anisotropy relationship. The findings have a two-way beneficial effect for the solution of a geotechnical boundary value problem, where one can easily measure initial elastic clay anisotropy in the field, which can be used to initialise the plastic anisotropy for the subsequent analysis of the problem, while the evolving plastic anisotropy can be used to update the elastic fabric tensor during deformation. [ABSTRACT FROM AUTHOR]

The cracking of clayey soils in seasonally frozen regions is affected by cyclic drying-wetting and freezing-thawing. Understanding the mechanism governing soil cracking behavior is crucial for the construction and long-term operation of infrastructures and earthworks. In this study, a series of laboratory tests were conducted on clayey soils, including freezing-thawing tests and evaporation tests. The evaporation rate and surface cracks evolution were monitored. The cracking mechanism of soils were analyzed. Results show that both the initially unsaturated and oversaturated soils exhibit an increase in evaporation rate with increasing freeze-thaw (FT) cycles in the early stage. Under the same FT and drying conditions, initially unsaturated soils show a higher evaporation rate in the early stage than oversaturated soils, followed by a lower rate after entering the residual stage. In addition, cyclic FT accelerates the propagation of the number of crack segments, surface crack ratio, and total crack length, but weakens the propagation of average crack width. Moreover, it was found that for initially unsaturated soils, desiccation-induced matrix suction plays a leading role in producing wide, rough, and curved desiccation cracking patterns. While for initially oversaturated soils, freezing-induced ice pressure/cryogenic suction dominates, resulting in short, fine, and straight frost cracking patterns. • Soil desiccation cracking depends on freeze-thaw cycle. • The evaporation rate in the initial stage increases with the number of freeze-thaw cycles. • Initial water contents and the number of freeze-thaw cycles significantly influence the evaporation process. • Evaporation and cracking mechanisms of soil subjected to freeze-thaw and wetting-drying cycles were revealed. [ABSTRACT FROM AUTHOR]

Recycled waste materials have been investigated in different ways in civil engineering applications and at these studies the usability of waste materials have been examined in concrete production, road construction and soil improvement. In this study, the effect of recycled nano carbon black (nano-CBr) on consistency limits and unconfined compressive strength properties of clayey soils was investigated. For this purpose, 4 different ratios (1%, 3%, 5% and 10%) nano-CBr were mixed to 3 different clay soils (White, Green and Red clays). In order to determine the mineralogical and chemical properties of mixtures, pH, TDS, X-Ray, SEM and contact angle tests were also performed. In this study, 1% nano-CBr ratio was generally determined as the limit value in all experiments. The consistency properties of the mixed samples have not significantly changed for the red and green clay but have importantly affected the white clay properties. Based on the 1% nano-CBr ratio, the unconfined compressive strength (UCS) values of all mixed samples increased. Addition of super hydrophobic nano-CBr to clay soils, turned clay soils into a hydrophobic material, is resulting in an increase in the contact angle values. On the other hand, pH values did not show a significant change with the increase of the nano-CBr ratio. The total dissolved solids (TDS) measurements showed a series of rise and fall steps with the increase of nano-CBr ratio and showed a tendency to stabilize at 10% nano-CBr ratio. [ABSTRACT FROM AUTHOR]

This work evaluates the behaviour of clay soil mixture by adding stell waste/slag, comparering with the quality criteria to be a subgrade road. The behavior of the mixture of steel waste with kaolinite clay was established with a dosage matrix of global increase, in percentages of 25, 50 and 75% through sieve number 4. The results show that the steel waste works on cohesive materials, reducing plasticity by up to 0%, and increasing the California Bearing Ratio (CBR) value, by 378.92%. It is possible to conclude that the steel waste is an excellent complement for improving the physical and mechanical properties of kaolinite clay subgrade. In a first approximation, the most recommended dosage is 25%, because the reduction of resistance to compression and plasticity index was not as high as in other dosages, but it increases the CBR index and the density. [ABSTRACT FROM AUTHOR]

Oedometer intrinsic compressibility of common inorganic soils can be explained with a few fundamental parameters obtained from simple laboratory tests. Specifically, on the basis of the liquid limit and clay percentage of a soil (fine or semi-fine), the coordinates of its intrinsic compression line can be calculated. Hence, by plotting both the oedometer compression curve of an undisturbed soil sample and the relative (measured or calculated) intrinsic compression line, the natural soil structure derived from its geological history can be estimated. Since the natural soils generally differ in mineralogical composition, the data normalisation appears to be of fundamental importance to evaluate the soil element structure in sedimentary soil profiles. The aim of this paper is to build a unique 'straight intrinsic compression line' SICL correlating the compression behaviour of soils with different mineralogical compositions based on the Burland's concept of evaluating soils structure. Specifically, it is possible to obtain the 'sedimentation compression curve' SCC of the intact soil elements down a sedimentary soil profile, which can be compared directly with the SICL and SCC of others soil profiles. [ABSTRACT FROM AUTHOR]

The corrosion of steels in clay soils is of interest for buried steel infrastructure. To obtain better information about the early corrosion effects, mild steel coupons were exposed for 3, 6 and 13 months in finely graded clay soil at different moisture contents and with different degrees of compression to simulate compaction. It was found that the maximum corrosion mass loss and pit depths occurred at a soil moisture content of 17–18 wt-% for all exposures and levels of compaction, corresponding to around 0.65 degree of saturation. These values are broadly consistent with earlier findings for non-clay soils. For exposures of 3 months corrosion was predominantly localised but subsequently became more uniform. This was shown to be consistent with good compaction of the soil against the steel surface. Poorly compacted lumpy clays, however, showed larger areas of localised corrosion and relatively greater corrosion mass loss and deeper pitting. [ABSTRACT FROM AUTHOR]

Vertisols are characterized by high content of clay fraction that affects their specific morphological and physical features. The shrink-swell phenomena of clayey materials under specific moisture regime cause formation of cracks, wedge-shaped structural aggregates and slickensides on aggregate surfaces. It was formerly believed that these soils can be found only in tropical/subtropical zones, thus Vertisols have not been expected to form under temperate climate of Central Europe. As a result, Vertisols are insufficiently recognized and documented on soil maps in Poland, including the Lower Silesia region. The aim of this study was to examine soils developed on clayey parent materials near Strzelin, focusing on their morphology, properties and classification issues. There was confirmed that soils developed from Neogene clays have vertic and mollic horizon, accompanied by stagnic or gleyic properties. However, not all soils fulfil the criteria for Vertisols due to the presence of surface or subsurface coarser-textured (sandyor silty-textured) layers. Native differentiation of parent material and geomorphological processes were found the main factors, which control the spatial mosaic of Vertisols and black earths (Chernozems or Phaeozems). [ABSTRACT FROM AUTHOR]

The shear modulus of soils at small strain (G0) is one of the input parameters in a finite element analysis with the hardening soil model with small strain stiffness, required in the advanced numerical analyses of geotechnical engineering problems. The small strain stiffness can be determined based on the seismic wave velocities measured in the laboratory and field tests, but the interpretation of test results is still under discussion because of many different factors affecting the measurements of the wave travel time. The recommendations and proposed solutions found in the literature are helpful as a guide, but ought to be adopted with a certain measure of care and caution on a case-by-case basis. The equipment, procedures, tests results and interpretation analyses of bender elements (BE) tests performed on natural overconsolidated cohesive soils are presented. [ABSTRACT FROM AUTHOR]

Upon completion of the operation on a site, spudcan foundations are pulled out of the seabed before relocating the jack-up platform to another candidate site. It is critical to predict the peak extraction resistance before commencing the jack-up extraction. Though sand-over-clay seabed is commonly found in active marine oil and gas exploration zones, the models for estimating the extraction resistance are very rare. This paper proposes a Bayesian prediction model based on 51 groups of centrifuge tests on foundations extracting from sand overlying clay soils. Model factors are introduced to define the uncertainties in the prediction. Combined with the monitored data during foundation extraction, possible breakout range of resistance and depth is predicted and updated in real time. The most likely breakout resistance and depth in the area are also estimated. The results show that (1) the predicted range of breakout resistance and depth may occur are concentrated around the measured values with the update of the monitored data; (2) the relative error between the most likely breakout depth and the measured value is kept within 10%; and (3) regardless the shape of the foundation, the Bayesian prediction model can effectively predict the extraction behaviour of the foundation. • The breakout resistance and depth for spudcan foundations extracting from sand-over-clay soils are predicted in real time. • The range of the predicted results concentrates to the measured breakout resistance and depth with increasing monitored data. • The relative error of the predicted breakout depth and resistance are within 10% and 20%, respectively. • The proposed method provides a powerful tool for the engineer for timely and safely extraction of jack-up foundations. [ABSTRACT FROM AUTHOR]

A series of lateral tests conducted in a centrifuge on displacement piles in kaolin is used to examine the effects of pile shape, pile end-condition and clay overconsolidation on the lateral load transfer (p–y) curves in soft clay. These experimental tests are supported by finite-element analyses, which examine the responses of the circular, square and H pile sections used in the centrifuge tests. The experimental and numerical results reveal an important effect of pile shape on p–y curves, but no discernible effect of the pile end condition. These results also indicate comparable dependencies of net ultimate pressures on normalised depth and undrained shear strength. The findings enable development of a new formulation for p–y curves in soft clay, which incorporates the effects of pile shape and uses the triaxial compression consolidated undrained shear strength as the reference undrained strength. [ABSTRACT FROM AUTHOR]

Pedogenesis has been previously proposed on the plateaus around Coprates Chasma, Valles Marineris to explain the presence of widespread clay sequences with Al-clays and possible hydrated silica over Fe/Mg-clays on the surface of the plateaus (Le Deit et al., 2012; Carter et al., 2015). We use previous observations together with new MRO targeted observations and DEMs to constrain the extent and thickness of the plateau clay unit: the Al-clay unit is less than 3 m thick, likely ∼1 m, while the Fe/Mg-clays underneath are few tens of meters thick. We also refine the age of alteration by retrieving crater retention ages of the altered plateau and of later deposits: the observed clay sequence was created by surface pedogenesis between model ages of 4.1 Ga and 3.75 Ga. Using a leaching model from Zolotov and Mironenko (2016), we estimate the quantity of atmospheric precipitations needed to create such a clay sequence, that strongly depends on the chemistry of the precipitating fluid. A few hundreds of meters of cumulated precipitations of highly acidic fluids could explain the observed clay sequence, consistent with estimates based on late Noachian valley erosion for example (Rosenberg and Head, 2015). We show finally that the maximum quantity of sulfates potentially formed during this surface weathering event can only contribute minimally to the volume of sulfates deposited in Valles Marineris. [ABSTRACT FROM AUTHOR]

Expansive clayey soils, which are prevalent across the surface sediments of the earth, are considered problematic for the structures and infrastructure founded in them. These soils are also challenging for environmental engineers involved in the design and construction of municipal and nuclear waste liners, petroleum engineers dealing with shale oil and gas, and agricultural scientists. Because their overall behaviour is controlled by molecular-level processes and interactions, a behaviour model encompassing the contributions from these interactions is required to predict the behaviour of these soils. This interaction becomes increasingly complex for natural expansive clays where a complex composition of clay and non-clay minerals exists. Unfortunately, none of the existing constitutive models pertaining to expansive clays comprehensively incorporates all the factors contributing to volume change behaviour of naturally occurring expansive soils. This study led to the development of a nano-level constitutive model for natural expansive clays through a three-phase study consisting of macro-level swell potential testing on laboratory control and natural field samples, micro-investigation of the pre- and post-swell specimens, and molecular level modelling through molecular mechanics, molecular dynamics and Monte Carlo techniques. This swell potential behaviour model incorporates all the major contributing factors such as moisture content, density, cation exchange capacity, exchangeable cations and interaction of clay minerals with non-clay minerals. The developed models have been successfully validated through close prediction of the swell potential behaviour of the laboratory control samples and natural field samples. [ABSTRACT FROM AUTHOR]

Equilibrium sediment volume (ESV) is used as an important parameter for understanding the expansive nature of the bentonites and natural clay soils, for assessing a given bentonite for engineering applications, and for the determination of the type of dominant clay mineral present in a given soil. The ESV is often estimated using different salt solutions to understand the compatibility of given clay soil for long-term engineering application such as landfills. A theoretical approach based on physicochemical behavior of clays was proposed in this paper for the estimation of equilibrium sediment volume of bentonites in the presence of salt solutions. A simple analytical expression relating equilibrium sediment volume with different influencing physicochemical parameters such as clay surface and pore-fluid parameters was presented using the diffuse double layer theory. A quantitative estimation of ESV by the proposed theory was validated on the measured data. A very good agreement between the theoretical and measured data was observed for the commercial bentonite. The theory was in good agreement with the measurements in the concentration range of 0.01 M ≤ n < 1 M for Kutch bentonite while the concentration range was 0.001 M ≤ n < 1 M for Barmer bentonite in NaCl solutions. The influence of different exchangeable cations and the presence of non-clay content on the prediction were analyzed with a great detail using theory and by comparing the ESV data of studied bentonites with the homoionic sodium clay. The parallel plate assumption made in the theory overestimated the ESV data in CaCl 2 solution. The proposed analytical model is very useful for understanding the influencing parameters on the bentonite behavior. [ABSTRACT FROM AUTHOR]

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Clayey soils exhibit a very pronounced time-dependent behaviour owing to their viscous properties. To analyse and to quantify these properties, two rounds of tests have been performed on a compacted clay. The first round, consisting of constant-strain-rate compression, stress relaxation and creep, shows that viscous properties are not influenced by different levels of stress and strain. Moreover, the influence of the loading frequency on the viscoelastic modulus is evidenced by the cyclic tests performed at very small strain amplitudes. The results of the second round, consisting of creep and stress-relaxation tests performed at different levels of stress and strain in triaxial loading-unloading-reloading phases and analysed by way of the viscoplastic mechanism terms from Perzyna's over-stress theory, show the existence of a primary yield mechanism activated at the maximum loading point. A kinematic mechanism becomes activated during the unloading and reloading phases, controlling from this moment on the viscoplastic behaviour within the primary yield locus. [ABSTRACT FROM AUTHOR]

A full-flow ball penetrometer is now routinely used in centrifuge testing for characterizing single-layer clay, silt, sand, and stratified soil samples. The behavior of the standard ball penetrometer (including the shaft) used in the field, penetrating through single and two-layer uniform clays, has recently been investigated. However, the ball penetrometers used in centrifuge testing has either a similar or higher area ratio (of the shaft to the ball) and significantly greater equivalent prototype diameter compared with the standard one used in the field. The thickness of the soil layers, however, are scaled accurately mimicking strength profiles in the field, leading to lower relative thickness of the soil layers. Large deformation finite element (LDFE) analyses were, therefore, carried out for the centrifuge ball penetrometers to investigate its performance in characterization of single- and double-layer clays. The results were validated against plasticity solutions and other previously published finite element (FE) results prior to undertaking a detailed parametric study, exploring a range of normalized soil properties and layer thickness. Three commonly used centrifuge balls were studied. For single-layer uniform clay, the area ratio of shaft to ball was shown to have significant influence on the deep bearing factors and the critical penetration depth of attaining that factor. For two-layer uniform clays, the undrained shear strength of the top layer was mostly underestimated because of the lower thickness of that layer relative to the centrifuge ball diameter. In addition, the shear strength of the bottom layer was mostly overestimated because of trapping of stiff clay at the base of the ball, advancing in stiff-over-soft clay deposits. To interpret a reference undrained strength profile, taking into account the scale effects of the penetrometer relative to layer thickness, a framework has been proposed accounting for these effects, with the LDFE data used to calibrate the framework. [ABSTRACT FROM AUTHOR]

This paper reports the results from three-dimensional dynamic finite element analysis undertaken to provide insight into the behaviour of torpedo anchors during dynamic installation in non-homogeneous clay. The large deformation finite element (LDFE) analyses were carried out using the coupled Eulerian–Lagrangian approach, modifying the simple elastic-perfectly plastic Tresca soil model to allow strain softening, and incorporate strain-rate dependency of the shear strength using the Herschel–Bulkley model. The results were validated against field data and centrifuge test data prior to undertaking a detailed parametric study, exploring the relevant range of parameters in terms of anchor shaft length and diameter; number, width and length of fins; impact velocity and soil strength. The anchor velocity profile during penetration in clay showed that the dynamic installation process consisted of two stages: (a) in Stage 1, the soil resistance was less than the submerged weight of the anchor and hence the anchor accelerated; (b) in Stage 2, at greater penetration, frictional and end bearing resistance dominated and the anchor decelerated. The corresponding soil failure patterns revealed two interesting aspects including (a) mobilization of an end bearing mechanism at the base of the anchor shaft and fins and (b) formation of a cavity above the shaft of the installing anchor and subsequent soil backflow into the cavity depending on the soil undrained shear strength. To predict the embedment depth in the field, an improved rational analytical embedment model, based on strain rate dependent shearing resistance and fluid mechanics drag resistance, was proposed, with the LDFE data used to calibrate the model. [ABSTRACT FROM AUTHOR]

Many offshore foundations can be approximately treated as circular footings. There have been a number of studies in the past few decades on the vertical bearing capacity of circular foundations, however, limited work has been reported for buried footings under horizontal loading. This paper presents the results of a numerical investigation into the undrained bearing capacity of conical footings in clay for both uniform and linearly increasing shear strength profiles. In total 1296 three-dimensional finite element limit analyses were conducted to investigate the horizontal bearing capacity, considering the effects of embedment ratio, foundation–soil interface roughness, conical angle and soil strength heterogeneity. The effects of each of the above critical factors on the horizontal bearing capacity are presented and discussed. The bearing capacity factors in this study are summarized in design tables, providing new solutions to improve the current design practice for conical footings in clay soils. [ABSTRACT FROM AUTHOR]

Soil is a multiphase material with irregularly shaped particles, the behaviour of which is highly nonlinear, anisotropic, and inelastic. Anisotropy and its evolution characteristics are crucial in soil's constitutive modelling, particularly for clayey soil. A new anisotropic constitutive model for remoulded clay is proposed based on improved yield surfaces and rotational hardening rules for initial and induced anisotropy. The logarithmic interpolation function is adopted to describe the volumetric deformation characteristics of clay in an arbitrary stress state, and a flexible yield surface shape is obtained by changing the newly introduced parameter n. This new parameter can be determined by fitting the undrained shear strength or stiffness of stress–strain curves. A key feature of the proposed evolutional rule for anisotropy is that the principal direction of the yield surfaces in the stress plane can be consistent with the isotropic stress axis when the critical state is reached. The proposed elastoplastic model shows good capacity for describing laboratory results from oedometer tests with constant stress ratios, reconsolidation tests with various stress ratios, triaxial compression tests, and triaxial extension tests under both undrained and drained conditions. [ABSTRACT FROM AUTHOR]

This paper focuses on nonlinear creep behavior with a consecutively decreasing creep coefficient Cae fully related to the soil density. Conventional oedometer tests on reconstituted samples of several natural soft clays are selected to clarify the evolution of creep coefficient throughout testing. On this basis, a simple nonlinear creep formulation is proposed accounting for the effect of volumetric packing of soil assemblies. The formulation is then incorporated into a newly developed elastic-viscoplastic model to take into account the nonlinear creep of natural soft clays. One additional parameter is added that can be determined in a straightforward way from an oedometer test without additional experimental cost. The enhanced nonlinear creep model is examined by simulating a conventional oedometer test on reconstituted Haarajoki clay. The improvement of predictions by the nonlinear creep formulation is highlighted by comparing predictions with constant Cae. The enhanced model is further applied to Murro test embankment. The influence of consideration of nonlinear creep on the embankment behavior is discussed. [ABSTRACT FROM AUTHOR]

Silt is available in many parts of the world in combination with sands and clays. However, due to lack of clear understanding of its engineering behaviour, most of the time it is interpreted in terms of either sands or clays. Structures that are usually built on silty soils are designed to take into account design procedures developed for sandy or clayey soils. Presence of silts in combination with varying amount of sand and clays produces silt that is either plastic or non-plastic in nature. Silt is available in and around the Delhi region, in a majority mixture along with fine sands, which is non-plastic in nature. On the other hand silty deposits found in offshore Bombay High region are found in abundance along with significant amounts of clays and are termed as plastic silts. In this paper a comparison of the stress-strain behaviour of plastic and non-plastic silts is carried out under triaxial compression loading during both drained and undrained conditions. Two representative samples each from Delhi and Bombay High regions were considered for this comparison and results of stress-strain under four sets of confining pressure are discussed in detail. It is observed from this study that behaviour of silts is mainly dependent on the composition and structure of the resultant soil matrix. It is concluded from the results that shear strength parameters as well as volume change/pore pressure response of silty soils is dominated by the constituent soil present along with the silt. It is seen from the comparative behaviour of non-plastic and plastic silts that the presence of sand and clays has a governing effect on pore pressure development and the resultant friction angle. The study also corroborated that the nature of silt is transitional both in the case of plastic and non-plastic forms. [ABSTRACT FROM PUBLISHER]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Understanding the fate and movement of contaminants through soil is essential in applications such as ecological and environmental risk assessment. Abundance of clayey soil is available across the world. Presented in this paper is a parametric study of the movement of contaminants through clays. The current paper provides a holistic approach addressing these issues by providing an understanding of the factors influencing movement of contaminants in soil strata using available numerical models (advection and dispersion) for contaminant flow through porous medium. A numerical model using the finite difference and finite element method is considered in this study to estimate the contaminant transport phenomenon presented by Zhao et al. (1994) that utilises the analytical solution proposed by Ogata and Banks (1961). The results and discussions of the parametric study highlight the influence of various properties of soil and the contaminant on permeability and concentration (contaminant) variation with time and depth. The finding indicates that the diffusion coefficient (Dx) plays an important role in determining the time taken for the concentration of contaminants to be evenly spread in a vertical direction. [ABSTRACT FROM AUTHOR]

This paper examines the strength characteristics of Portland cement-treated fat and lean clays (CH and CL) under the conditions of freeze–thaw cycles. Specimens of natural clays were mixed with Portland cement in different percentages of 5% and 10%, in terms of the dry mass of soil using two different water contents of 30% and 50% for CH type of clay soil and 20% and 30% for CL type of clay soil to represent different consistencies and workability of soils. Besides, a group of cement free specimens was prepared and/or a group of specimens was not subjected to freeze–thaw cycles for comparison reasons. All specimens were cured for 7 and 28 days in a humidity controlled room at a constant temperature. After curing, specimens were subjected to a maximum of five cycles of closed-system freezing and thawing. Unconfined compression tests and ultrasonic pulse velocity tests were conducted on the specimens. The results of unconfined compression tests were evaluated in terms of water–cement ratio, curing period and the number of freeze–thaw cycles. Consequently, the compressive strength increased with the cement content increment of the clay specimens. While the specimens with highest cement content showed brittle behavior before freeze–thaw tests, they manifested less brittle behavior after freeze–thaw tests. The highest strength values were obtained in the specimens with low water contents. The compressive strength decreased as the freeze–thaw cycles increased, but cement treatment partially prevented the strength loss in freeze–thaw conditions. Generalized equations of strength development were assessed considering the total water–cement ratio and curing time effects for fat and lean clays that were subjected to 0, 1, and 5 cycles of freeze–thaw tests. In this way, this study showed that clay water–cement ratio hypothesis can be used to analyze the strength development of clays at different freeze–thaw cycles. It was observed that a linear correlation existed between the ultrasonic pulse velocity and the unconfined compression strength values. Furthermore, the plasticity index of the specimens subjected to 5 freeze–thaw cycles showed a decrement for the clay which was highly plastic in its native condition. Finally, with this study it is proven that cement treatment techniques can be preferred to enhance the freeze–thaw durability of fat and lean clay soils. [ABSTRACT FROM AUTHOR]

Ground movements observed during foundation installation and basement construction of a residential 53-story RC tower are presented. The One Museum Park West building is located in Chicago, Illinois, and was developed using a combination of bottom-up methods, used for the construction of a central concrete core of the building, and top-down methods to build five levels of basements. The excavation extended 13-15 m below grade and was made through soft to medium-stiff clays. The building was supported by drilled shafts and a perimeter wall formed by secant piles that transitioned to tangent piles below the bottom of the cut. The system was laterally braced with RC floor slabs structurally connected to the secant pile walls and the RC core. Field performance data were collected by means of settlement points and inclinometers located close to the walls on two sides of the excavation. The construction sequence and attendant ground movements during each main activity are summarized. As much as 160 mm of settlement was recorded in the adjacent streets throughout construction. Wall and foundation installation accounted for approximately 35% of the total settlements during construction, whereas top-down construction of the basement resulted in approximately 40% of the total settlements. These data emphasize the importance of considering all construction activities when making predictions of ground movements adjacent to deep supported excavations. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental study of the influence of clay content (CC) on liquefaction of seabed beneath progressive waves. Experiments were, for the most part, conducted with silt and silt-clay mixtures; in supplementary tests, sand-clay mixtures were used. Two types of measurements were carried out: (1) pore-water pressure measurements across the soil depth and (2) water-surface elevation measurements. These measurements were synchronized with video recordings of the liquefaction process from the side. The ranges of the various quantities in the experiments were wave height , wave period , and water depth . The experiments showed that the influence of CC on wave-induced liquefaction is very significant. Susceptibility of silt to liquefaction was increased with increasing CC up to (which is clay-specific), beyond which the mixture of silt and clay was not liquefied. Sand may become prone to liquefaction with the introduction of clay, contrary to the general perception that this type of sediment is normally liquefaction-resistant under waves. For instance, sand with was liquefied with , whereas sand with was partially liquefied with CC as small as 2.9%. Remarks are made as to how to check for liquefaction of clayey soils exposed to waves in real-life situations. [ABSTRACT FROM AUTHOR]

Predicting the compaction parameters, in terms of maximum dry unit weight and optimum water content, from index properties of fine-grained soils has been of interest for the last few decades. Although various index properties, such as liquid limit, plastic limit and clay contents, have been used for the prediction, it was revealed that plastic limits of fine-grained soils correlate well with the compaction parameters. As an alternative method, this paper proposes sediment volume test to estimate the compaction parameters. In order to show its relevance, compaction and sediment volume tests were performed on nine fine-grained soils. The final sediment volumes (FSVs) of soils were determined from sediment volume tests. Then, the correlations between compaction parameters and FSVs were investigated. It is found from this experimental investigation that there is a good relationship between the compaction characteristics namely maximum dry unit weight (γ dmax ) and optimum water content (w opt ) and the FSV, indicating that this method can be used as an alternate way of predicting the same. [ABSTRACT FROM AUTHOR]

The Earth's polar regions are experiencing a greater frequency of freeze-thaw events throughout the polar summer, contributing to atmospheric methane and destabilising clay-rich sediments. Clays in soils tightly bind pore water and thus substantially modify freeze-thaw events. While temperatures of phase transitions for confined pore water may be precisely assessed using calorimetric or thermal analyses to −30 or −40 °C, neutron scattering directly probes how pores in clay minerals control ice formation and melting to lower temperatures. We apply elastic neutron scattering to accurately quantify the unfrozen water content of clay gels and unambiguously identify different pore-water environments by their freezing temperatures. Using this approach, we conclude that cryosuction controls water mobility in frozen soils in the absence of soluble salts to much lower temperatures than observed by other techniques. Dyanmics determined from neutron scattering indicates that water in clay gel pores thaws at much lower temperatures than currently considered, and thus pose potential risks for contaminant migration at sub freezing temperatures. The general poor strength of wet clays can significantly impact infrastructure in cold regions undergoing an increased frequency of freeze-thaw events. Different pore water environments in clay gels can be identified and quantified by inelastic neutron scattering. [Display omitted] • Cryosuction removes interlayer water from clay gels hydrated to near saturation. • Cryosuction requires capillary connectivity to operate in clay gels. • Considerable interlayer water remains unfrozen in clay gels to below −80C. • Freezing characteristic curves can be used to identify pore environments. [ABSTRACT FROM AUTHOR]

In this paper, a multi-surface anisotropic constitutive model is proposed for clayey soils, based on bounding surface theory and a classical anisotropic critical state-based model. In the proposed model, in addition to the volumetric hardening law, a rotational hardening rule is also incorporated into the bounding surface formulation with a non-associated flow rule. The model uses the bounding surface plasticity theory to produce a more realistic representation of the nonlinear behavior of clays with high overconsolidation ratios. Detailed model formulation is presented including an innovative approach to find image stress points on the bounding surface which offers an original conception of changing the projection center, even at the absence of plastic loading. A modified procedure is also discussed to improve the performance of the proposed model for simulating the response of highly overconsolidated clays. The proposed modifications, together with the novel mapping rule, form a new framework that can be used to improve the simulation capabilities of different constitutive models that have elliptical yield/bounding surfaces. The efficiency of the framework is demonstrated by comparing the simulation results against element test data from a number of different clays at lightly to highly overconsolidated conditions. The new model shows promising capabilities in capturing the important aspects of natural clays response during straining, in particular for the combined effects of small strain nonlinearity with fabric orientation. [ABSTRACT FROM AUTHOR]

• Sporosarcina pasteurii is used to improve natural soft clays properties by MICP. • Concentration of urea and Ca2+ influences the efficiency of CaCO 3 precipitation. • Mechanical and chemical properties of MICP-treated clays are investigated. • Microstructures of MICP-treated clays are observed using SEM-EDX. • Comparisons of MICP efficiency on different clay types are presented. Microbially-induced calcite precipitation (MICP) is a promising technique to improve the engineering properties of soft soil in a sustainable, environmentally friendly, and energy saving manner. This study determined the suitable chemical condition to induce MICP activity from alkaliphilic urease-producing Sporosarcina pasteurii bacterium, and to explore the MICP activity's effectiveness in improving the mechanical properties of three types of natural fine-grained soils (Kaolin clay, Laterite, and Bangkok clay). Untreated and treated clays were evaluated by the free-free resonant frequency test, unconfined compression test, and their microstructures and chemical compositions. The results showed that a urea-Ca2+ input rate of 7.5 mmol/h efficiently promoted the precipitation of calcite by bacteria, as indicated by the highest degree of media clogging in sand column tests. A higher urea-Ca2+ input rate created soil samples that exhibited a high degree of supersaturation, which impacted the precipitation pattern at the microscale, resulting in less contact between soil particles; this was caused by the increase in salinity of the solution to a level that inhibited bacterial activity and retarded calcite precipitation. Once the optimal urea-Ca2+ input rate was determined, bacterial cultures were introduced into samples of each clay, and fed with the optimal chemical mixture while being maintained at room temperature (25–30 °C) for 7 d. Increases in the samples' stiffness and shear strength coincided with increased amounts of precipitated calcite. Enhancements to each clay type's strength parameters were dependent on the natural characteristics of clay. Specifically, liquid media carrying the necessary nutrients for MICP activity could not efficiently permeate through the clayey soil with a high plasticity, resulting in a lower observable degree of MICP activity to improve the soil's characteristics. [ABSTRACT FROM AUTHOR]

The extent, timing, and magnitude of soil moisture in wetlands (the hydropattern) is a primary physical control on biogeochemical processes in desert environments. However, determining playa hydropatterns is challenged by the remoteness of desert basin sites and by the difficulty in determining soil moisture from remotely sensed data at fine spatial and temporal scales (hundreds of meters to kilometers, and hours to days). Therefore, we developed a new, reflectance-based soil moisture index (continuum-removed water index, or CRWI) that can be determined via hyperspectral imaging from drone-borne platforms. We compared its efficacy at remotely determining soil moisture content to existing hyperspectral and multispectral soil moisture indices. CRWI varies linearly with in situ soil moisture content (R2 = 0.89, p < 0.001) and is comparatively insensitive to soil clay content (R2 = 0.4, p = 0.01), soil salinity (R2 = 0.82, p < 0.001), and soil grain size distribution (R2 = 0.67, p < 0.001). CRWI is negatively correlated with clay content, indicating it is not sensitive to hydrated mineral absorption features. CRWI has stronger correlation with surface soil moisture than other hyperspectral and multispectral indices (R2 = 0.69, p < 0.001 for WISOIL at this site). Drone-borne reflectance measurements allow monitoring of soil moisture conditions at the Alvord Desert playa test site over hectare-scale soil plots at measurement cadences of minutes to hours. CRWI measurements can be used to determine surface soil moisture at a range of desert sites to inform management decisions and to better reveal ecosystem processes in water-limited environments. [ABSTRACT FROM AUTHOR]

Thermomechanical behaviour of clay has been widely investigated by well-controlled laboratory experiments, while in-situ test of thermal effects on soil is rare. The piezocone penetration test (CPTU) is first used in this study to directly evaluate the temperature effects under in-situ stress condition. A full-scale precast high strength concrete (PHC) pile was utilized as the heat source and a series of CPTU were conducted in adjacent layered clays after monotonic heating and thermal cycle. The results show that unprecedented temperature elevation leads to an apparent reduction of soil strength in all soil layers; this degradation was alleviated after the thermal cycle. After exposure to a higher temperature, the normally consolidated soil was improved even when tested at a lower elevated temperature; whereas, the overconsolidated soil could nearly recovered to the pre-heated value. The measured pore pressure (u 2) also decreased after heating indicating a more overconsolidated or dilatant behaviour during shearing. By comprehensively considering the in-situ responses, the in-situ soils were believed to be unloaded by the thermally induced pore fluid pressurization and densified after cyclic thermal loading. Finally, a hypothesis is proposed to qualitatively explain the thermomechanical responses of in-situ soil in the framework of critical state soil mechanics theory. • The in-situ thermo-mechanical responses of soils were tested by CPTU. • The in-situ soil strength decreased under unprecedent elevated temperature. • Temperature cycles can alleviate in-situ strength degradation or improve the soils. [ABSTRACT FROM AUTHOR]

Proper understanding of the field performance of lime-treated expansive soils requires the evaluation of their unsaturated properties under stress conditions similar to that in the field. This paper studied the influence of net vertical stress on the soil-water characteristic curves (SWCC) of lime-treated expansive clay. The first phase of this study investigated the influence of lime content and curing period under low net vertical stress (7 kPa) using axis translation and filter paper techniques with simultaneous measurements of sample volume change. The second phase evaluated the SWCCs of untreated and lime-treated clays under vertical stresses of 100 and 600 kPa. Different representations of SWCCs were considered in the interpretation of test results. Test results indicated that lime content had a significant effect on the shape and air entry value of SWCCs because of changes in soil microstructure, whereas curing period had a far less significant effect. Furthermore, the application of net vertical stress delayed the desaturation of samples causing increase in air entry value. On the basis of plots for the variation of void ratio versus suction, the increase in air entry value was attributed to considerable reduction in volume (void ratio) associated with the application of the net vertical stress causing samples to remain saturated up to high suctions levels. [ABSTRACT FROM AUTHOR]

Laboratory and field investigations were performed in this study to evaluate the efficacy of a fine-grained clayey soil as a low-cost primary liner material for attenuating chrome-laden leachate from a chrome sludge disposal site of a tannery plant. On-site soil and water samples exhibited the existence of in excess of the permissible limit as prescribed for discharging inland surface water. Batch adsorption kinetic results showed that removal in equilibration increases with elevation of temperature. The soil mass in use exhibited reasonable capability of adsorbing , and the kinetic results demonstrated that the pseudo second-order kinetic model fitted reasonably well. The triaxial test results revealed a maximum permissible overburden pressure of from deposited waste if the clayey soil is to be used as a liner material. The use of a compacted clay soil with a thickness of 600 mm is recommended for effective containment of leachate transmission with regard to a leachable hexavalent chromium with an initial concentration of . [ABSTRACT FROM AUTHOR]