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The main objective of this study was to provide a methodological insight in the archaeometric field of ceramic provenance and technology, through the identification of the scale of representative differences in terms of clay composition. For this purpose, a total of 78 clay specimens-representative of the three types of Daunian clayey raw materials (Sub-Apennine clays, alluvial deposits and terraced alluvial deposits)- was collected and geochemically investigated, with the aim of determining up to which geographical scale, the exclusive application of geochemical analyses can provide reliable results for the reconstruction of clayey raw materials supply. For the Daunian territory, the scale has been identified with that of a ‘riverine province’, i.e. between the local and the regional extension of the north Apulian fluvial courses. In practice, the Sub-Apennine clays can be chemically distinguished into a northern group, including the Salsola, Vulgano, Celone and Lorenzo streams and a southern group, including the Carapelle stream and the Ofanto river. Moreover, the comparison between the geochemical composition of the clay samples and that of local ceramic productions (previously investigated) has shown that the Sub-Apennine clays were either used as received (Clay 1 group) or refined through decantation (Clay 2 group), before being shaped into fine wares or building materials; conversely, both the alluvial and the terraced alluvial deposits were used “as received” for the production of coarse wares. Furthermore, for the first time, the geospatial network analysis was further applied to the investigation of ancient raw materials exploitation. This analysis was performed in order to reach a reasonable reconstruction of both routes and travel times linking supply areas with production and distribution sites. Surprisingly, the results have shown that, at small distances, the transportation of clayey raw materials is not only reliable but rather highly likely, especially in those sites where Sub-Apennine clays are not readily available. [ABSTRACT FROM AUTHOR]

Clay soils are widely distributed throughout the world and are the source of multiple technical problems in their application for the construction of sub-grade and sub-road bases. These types of soils are found in areas where civilian infrastructure such as roads and rural roads must be built. Therefore, in many situations it is necessary to use stabilized expansive soils, in the formation of the foundation and structural layers of linear infrastructures. Soil stabilization is used to increase the load capacity of the soil, and mixtures of lime and cement are generally used as binders. In recent years, interest in the recycling of industrial products and by-products has increased. One example of this is the use of biomass combustion in power plants. The management of significant amounts of waste (biomass bottom ash) from biomass power plants remains a problem. This paper presents the results of an experimental study for stabilizing expansive soil to determine its bearing capacity and mechanical properties via a triaxial test of the addition of biomass bottom ash. A double objective was targeted: reduction of the problems in using this type of soil and provision of a use for this type of waste. The results showed significant improvements in the mechanical. Therefore, herein is proposed the use of biomass bottom ash as a stabilizing agent for expansive soils, to improve the efficiency of the construction process by incorporating this product into a second life cycle as road bases. [ABSTRACT FROM AUTHOR]

A snowpack is known to affect landslide stability as the snow loading changes. Furthermore, the snowpack can have effects on the hydrological behavior in the landslide mass. To clarify the response of pore water pressure to snow loading, continuous field-based monitoring of hydraulic and meteorological factors in landslides was conducted for a deposit of extremely low-permeability “quick clay” in Mid-Norway. The pore water pressure increased during every snow-covered period. The pressure exhibited little response to meltwater and/or rain, but corresponded closely to changes in snow accumulation. The increase in pore water pressure during the snow-covered period was considered to be excess pore water pressure generated by undrained snow loading on the extremely low-permeability quick clay. The pore water pressure displayed a positive linear relation with the snow load, and the ratio of the increase in the pore water pressure to the snow load ( ru snow ) was 0.49–0.53. These values show that approximately half of the snow load contributed to the excess pore water pressure. Continuous field-based monitoring was also conducted for another landslide in relatively high-permeability deposits in Japan, where the pore water pressure showed a relatively low ru snow of about 0.15 and a different timing of the pressure peak. This comparative result indicates that the response characteristics of pore water pressure to the snow loading are strongly affected by the permeability of the landslide mass. Although the excess pore water pressure generated by the snow load theoretically had a negative effect on the slope stability, the value of excess pore water pressure at the monitored landslide was relatively too small to affect its stability. [ABSTRACT FROM AUTHOR]

Naturally deposited clays are generally K 0 consolidated. In some cases such as embankment construction and foundation pit excavation, the loading or unloading will lead to the re-consolidation of clays, which can be simulated by a simplified consolidation stress path with a certain ratio of vertical to horizontal consolidation stresses. In this study, a series of triaxial shear tests was conducted on a reconstituted Wenzhou clay, to investigate the effects of consolidation stress paths on the stress-strain, pore water pressure-strain, and effective stress path behaviors of overconsolidated samples. Based on the test results, the shear strength and pore water pressure coefficient at failure are found to grow and reduce linearly with the increase of the ratio of vertical to horizontal consolidation stresses, respectively. More strain softening and shear dilation are observed for the anisotropically consolidated samples compared to isotropically consolidated ones. The slope of failure line is approximately 1.25 for all specimens tested in this study. [ABSTRACT FROM AUTHOR]

This study explores the possibility of substituting clayey raw materials using ceramic sludge in clay roof tile production. The tile specimens were manufactured in an industrial scale plant by replacing clay with ceramic sludge: 0%, 10%, 15%, 20% and 25% (by weight). Strength properties (transverse breaking strength, modulus of rupture, bulk density), durability properties (water absorption, water penetration, salt crystallization, efflorescence, acidic and alkaline resistances) and run-off qualities (Ph, total solids, BOD, heavy metal concentration) were examined. Thermal properties of the sludge incorporated tiles were investigated and compared with the conventional tiles. Bulk density reduces with increasing the sludge content, which is a favorable property of roof tiles. Transverse breaking strength was optimum at 20% sludge, indicating 22.9% increment compared to the conventional tile. Clay replacement up to 20% is acceptable, satisfying water absorption and penetration in standards. No efflorescence and Sulphuric acid attack were disturbed for any specimen. At 12:00 noon, the tile with 20% sludge reduced indoor temperature by 2.8 °C, providing more comfortable shelter compared to the conventional roof tiles. For the 25% sludge incorporated tiles, run-off showed 120.2 mg/l total solid concentration, 7.36 Ph value and 5 mg/l BOD5 value, 0.01 mg/l, 0.05 mg/l, 0.06 mg/l, 0.04 mg/l Cd, Cu, Pb and Zn concentrations, respectively; while for the other tiles, run-off had lesser concentrations, which are favorable for rain water harvesting process. With 20% sludge, tiles achieved better structural, durability and thermal properties compared with the conventional tiles while satisfying the standard limits of run-off qualities. [ABSTRACT FROM AUTHOR]

The exterior surfaces of cast iron pipes buried in clay soils for up to 129 years show clustering of pits of similar depth at progressively greater overall corrosion pit depth. Within experimental accuracy, the pit depth increments are approximately constant over the whole range of pit depth for each soil. They increase with lower soil pH and appear insensitive to other soil properties and to burial period. These new findings are interpreted relative to pitting electrochemical potential and compared with field observations for pitting in marine corrosion of steel. Implications for modelling maximum pit depth development are considered. [ABSTRACT FROM AUTHOR]

Soil bin investigations were initiated with combined offset disc harrow (CODH) which unites the benefits of powered discs and combination tillage together through a front active-rear passive set configuration. The proposed configuration may help to achieve timeliness in sowing, better crop residue handling with reduced tillage passes and improved engine power utilization of tractor. The effects of speed ratio (u/v), front gang angle (α), operating depth and cone index (CI) on its draft, torque and power requirement were studied and compared with its traditional passively driven mode at an average soil moisture of 9–10% (db) in sandy-clay loam soil. Optimum system settings were found out before further performance evaluation in the field. The substantially reduced draft requirement with CODH might help to reduce the wheel slippage and improve field productivity while increased power requirement might prevent the under-loading of tractor engine. Tillage quality was assessed considering CI values and found to be far superior compared to traditional mode. Optimum system settings were found at α of 35° and u/v ratio of 3.6 in terms of lowest power expenditure and better work quality with torque power expenditure of 60–70% in total power indicating improved utilization of engine power if operated with tractor power take-off (PTO). [ABSTRACT FROM AUTHOR]

The purpose of this paper is to predict the rolling resistance of a free rolling off-road truck tire (size 315/80R22.5) over several soils. The soils are modelled using Smoothed-Particle Hydrodynamics (SPH) in the software package “Pam-Crash”. The soil models are calibrated using data obtained from published pressure-sinkage and shear-strength tests. The truck tire used in this study was modelled using Finite Element Analysis (FEA) and validated in previous studies. The tire-soil interaction algorithm is implemented in Pam-Crash software package to capture node-symmetric node-to-segment contact with edge treatment. The rolling resistance coefficient is computed from simulations and then validated against physical measurements. The rolling resistance coefficient is calculated for different terrains, such as dry sand, dense sand, clayey soil and hard surface. In addition, the rolling resistance is also computed for various tire inflation pressures and applied vertical loads. The research results presented in this paper will be further used for soil mixing-layering investigation. [ABSTRACT FROM AUTHOR]

Emissions of greenhouse gases (GHGs), such as carbon dioxide (CO 2 ) and nitrous oxide (N 2 O) have great impact on global warming and atmospheric chemistry. Biochar addition is a potential option for reducing GHGs emissions through carbon (C) sequestration and N 2 O mitigation. However, the influences of biochar on C and nitrogen (N) transformations in soil are still unclear, resulting in a poor understanding of the mechanisms of N 2 O mitigation effects of biochar. Here we carried out two soil incubation experiments to investigate the influence of two common biochars addition (corn cob and olive pulp) with ammonium sulfate on CO 2 and N 2 O emissions from two contrasting soil types (acidic sandy and alkaline clay soil). Furthermore, four extracellular enzymes activities that related to C and N cycling, i.e. cellobiohydrolase, chitinase, xylanase and β-glucosidase, were analyzed to gain insights into the underlying mechanisms of biochar’s effects on CO 2 and N 2 O evolutions. Contrasting effects of two biochars on CO 2 and N 2 O emissions were observed in the two different soils. The corn biochar addition had no significant effect on CO 2 and N 2 O emissions in the alkaline clay soil, but significantly decreased CO 2 emissions by 11.8% and N 2 O emissions by 26.9% in the acidic sandy soil compared to N-fertilizer only treatment. In contrast, olive biochar addition showed no significant effect on CO 2 emissions but decreased N 2 O emissions by 34.3% in the alkaline clay soil, while in the acidic sandy soil addition of olive biochar triggered about a twofold higher maximum CO 2 emission rate and decreased N 2 O emissions by 68.4%. Up to 50–130% higher specific CO 2 emissions (per unit of C-related enzyme activity: cellobiohydrolase, chitinases and β-glucosidase) were observed after addition of olive biochar compared to corn biochar addition in the acidic sandy soil. We concluded that biochar’s effects on N 2 O and CO 2 emissions are more pronounced in acidic soils. Alkaline biochar’s N 2 O mitigation potential in acidic soils seems to be dependent on soil NO 3 − content as drastically higher N 2 O emissions were measured in early phase of the experiment (where soil NO 3 − was high) and significantly lower N 2 O fluxes were obtained in later phases (with lower soil NO 3 − content). [ABSTRACT FROM AUTHOR]

Contamination of arid and semi-arid ecosystems by toxic heavy metals is a serious concern due to its impact on growth and productivity of crop and health risk through food chain. Therefore, the aims of this investigation were to study the impact of inorganic (i.e. nano hydroxyapatite, NHA and polyacrylamide, PAM) and organic (i.e. sugar beet factory lime, SBFL and biochar, BI) soil amendments on maize productivity grown in contaminated silty clay (i.e. fluvial, lacustrine) and sandy (i.e. marine) alkaline soils. In addition, the effect of those amendments on the content of heavy metals in plant organs and their fractions in alkaline soils at harvest as well as human health risk assessment were investigated. Application of amendments, particularly SBFL, followed by NHA and BI resulted in an improvement for maize growth and its productivity in comparison to PAM application and untreated soil. However, application of NHA significantly reduced the mobile fraction of Cd, Pb and Ni in soil and consequently in different maize organs, followed by application of SBFL and BI in comparison to untreated soil or soil treated with PAM. Additionally, transfer factors and health risk of metals were lesser when NHA and SBFL were applied into soil than those obtained from application of PAM. In conclusion, applications of NHA, SBFL and BI into contaminated alkaline soils with toxic heavy metals can be considered a vital option for ameliorating such soils from the view of environment and sustainable management in terms of heavy metals immobilization and reducing the metals content in plant organs. [ABSTRACT FROM AUTHOR]

The use of various wastes in the manufacture of different ceramic products has proved to be beneficial from both economic and environmental points of view. In the present paper, the simultaneous reuse of ceramic sludge waste (from 0% to 6.2%) and cullet (from 0% to 10%) in the production of vitrified clay pipes has been investigated. Samples were pressed at 15 MPa, dried and subsequently fired at three different temperatures (1050, 1150 and 1250 °C) and soaking times (1, 2 and 3 h). A two-level factorial design was applied to study the effect of the various parameters on the properties of fired bodies. It was concluded that an economic recipe can be prepared involving the use of 6.2% sludge (dry basis) and 5% cullet with the balance clay + grog followed by firing the dried body at 1050 °C for one hour only. The produced fired specimens yielded bending strength exceeding the minimum requirement for any size of soil embedded pipes and for 8″ and larger concrete cradled pipes. The suggested composition makes use of an environmentally polluting waste (sludge) and broken glass waste (cullet) and involves firing for one single hour at a temperature about 200 °C lower than commonly used. [ABSTRACT FROM AUTHOR]

In this paper, we propose an isotropic hardening elastoplastic model for structured marine clay that can describe its strength and deformation behavior under general loading conditions. A series of drained true triaxial tests were performed on structured and remolded marine clay to investigate the effect of intermediate principal stress. The test results show that the intermediate principal stress has a considerable effect, not only on the strength, but also on the deformation behavior of marine clay. A modified stress-dilatancy equation is defined in transformed stress space to capture this feature. Then, the model is extended to consider the influence of structure by incorporating the superloading surface concept. Compared with the modified Cam-Clay model, the proposed model requires only two additional parameters, which can be determined conveniently from triaxial and oedometer tests. The proposed model was validated by performing undrained triaxial tests and drained true triaxial tests at various confining stresses and Lode angles, respectively, on remolded and structured clay. [ABSTRACT FROM AUTHOR]

The post-cyclic undrained shear characteristics of marine silty clay was investigated by conducting a series of cyclic triaxial tests on undisturbed specimens. The effects of confining pressure, initial undrained shear stress ratio ( q s / p 0 ), cyclic stress ratio ( q cy / p 0 ) and number of cycles ( N ) on the post-cyclic undrained shear behavior were investigated. Results show that the post-cyclic shear strength decreases with the increase in q s / p 0 , q cy / p 0 and N . The confining pressure has no apparent effect on the normalized post-cyclic monotonic undrained shear strength for the silty clay. During the post-cyclic shear, the specimens with small q s / p 0 and q cy / p 0 contract, while the cases with large q s / p 0 and q cy / p 0 dilate. Also, the terminal value of normalized post-cyclic shear-induced excess pore pressure decreases with q s / p 0 or q cy / p 0 increasing. The Equivalent Hvorslev Line (EHL) was proposed to form a failure envelop for the post-cyclic silty clay and the slope of EHL increases with the increase in q cy / p 0 or q s / p 0 , regardless of the number of cycles. Moreover, a post-cyclic strength model, which could consider the influence of initial shear stress and previous cyclic loading history was proposed on the basis of Yasuhara model. This model demonstrates a good agreement with the test results. [ABSTRACT FROM AUTHOR]

Scour induces the loss of soil support around the pile foundations for the offshore and coastal structures, and thus increases their bending moments and lateral deflections, which may change the vertical loads effect on the lateral response of piles applied in such cases. In this paper, the stress changes of the remaining soils at the corresponding pile location due to the three-dimensional scour-hole formation are first determined based on the Mindlin's elastic solutions. Then, the calculated new soil stresses are adopted to re-examine the Young's modulus of the remaining soils undergoing a stress history due to scour. With this key soil parameter that have been modified appropriately to reasonably reflect the effects of three-dimensional scour-hole geometry and the stress history of the soils simultaneously, an analytical model based on the principle of minimum potential energy is further developed to investigate the influence of vertical loads on the lateral responses of offshore piles in marine clay under scour conditions. The influence of related parameters including the lateral displacement level and the vertical load level with different scour-hole dimensions (i.e., scour depth, scour width and scour-hole slope angle), considering or ignoring stress history effect, have also been analyzed based on a case study. The results show that scour depth plays the most important role among the various scour-hole dimensions in influencing the responses of scoured piles under combined vertical and lateral loading. Although still possessing some limitations (e.g., the simplistic assumption of linear-elastic behavior for the soil and the approximate allowance made to account for the gapping effect), the simplicity and relative ease of utilization offered by this proposed analytical model make it a good alternative approach for estimating the deflection and moment responses of the scoured pile foundations subjected to combined lateral and vertical loading. [ABSTRACT FROM AUTHOR]

This study shows that the controlled dispersion and distribution of nanoclay in clay/polyethylene (PE) nanocomposites result in peelable sealants with an ultra-wide peelable heat-seal temperature window (ΔT p ). Different nanoclays, unmodified montmorillonite (Mt) and organo-modified Mt. (OMt), were examined for their capacity to generate peelable clay/PE nanocomposites in a melt-blending film extrusion process. Clay/PE nanocomposite films containing 6 mass% organoclay (OC) exhibited a cohesive peel behavior with a ΔT p of about 12°C while PE film containing 6 mass% unmodified clay resulted in microcomposite with a lock seal performance. With the same mass% of OC, a much lower peel strength with a significantly broad ΔT p of 45°C was achieved mainly due to the fine dispersion of OMt when PE-grafted-maleic anhydride (PE-g-MA) was used as a compatibilizer. WAXD and TEM results confirmed that a substantial enhancement in the dispersion and distribution of intercalated nanoclays was achieved with PE-g-MA compatibilizer. Finally, an ultra-wide ΔT p of over 100°C was obtained for compatibilized OC/PE nanocomposite sealant containing only 3 wt% OC with partially exfoliated microstructure indicating that the exfoliation of nanoclay is in favor of peelability. The peel fracture mechanics of the clay/PE nanocomposite sealants were examined through T-peel test and SEM imaging. The results showed that the dispersion and distribution of nanoclay along with the interfacial adhesion between nanoclay and matrix are the key factors controlling the peel performance of the sealants. [ABSTRACT FROM AUTHOR]

In order to explore the feasibility of improving zinc and chromium ability of zirconium-aluminium pillared clays (PILC), mixed zirconium-aluminium PILC with different Zr/Al ratio (Zr/Al = 100/0, 90/10, 50/50, 10/90 and 0/100) were prepared and investigated for their ability to remove zinc and chromium from water. Single and mixed PILC were characterized with X-ray diffraction, N 2 adsorption–desorption, FT-IR spectroscopy method, etc. Results indicate that, in the case of single PILC, zirconium PILC exhibited an adsorption capacity higher than aluminium PILC. In the case of mixed PILC, adsorption capacity increased as the ratio of Zr/Al increased. The influence of the pH values and the temperature on adsorption capacity was also investigated. [ABSTRACT FROM AUTHOR]

Marl was treated with Mg-rich lime to evaluate the effectiveness of lime stabilization for this expansive, clay- and carbonate-rich material. XRD and TEM analyses revealed very limited dissolution of expandable clay minerals and neoformation of Mg-enriched smectites. C-(A)-S-H phases formed and initially cemented clay particles. However, they experienced decalcification and decomposition over time, leading to disaggregation of clay particles and deterioration of some of the marl's geotechnical properties. Results question the effectiveness of lime stabilization for marls, especially using Mg-rich lime. Modifications to commonly used treatment protocols in order to overcome these shortcomings are discussed. [ABSTRACT FROM AUTHOR]

Studies of the volume change behaviour of saturated and unsaturated fine-grained soils upon exposure to various types of fluid are of significant interest while dealing with contaminated soils. In this study, the one-dimensional volume change behaviour of two clays (Spergau kaolin and Calcigel bentonite) with dominant minerals as kaolinite and montmorillonite was studied by inundating several initially unsaturated and saturated clay specimens with water and a non-polar organic liquid (heptane). For both cases, applied vertical pressures of 25 and 100 kPa were considered under oedometric conditions. The magnitude of compression and swelling deformations of the clays were found to be strongly dependent upon the mineralogy of clays, dielectric properties of the pore-fluid, initial compaction conditions, and applied stress during the wetting process. The test results indicated distinct interactions between unsaturated clays and water. Specimens of Spergau kaolin exhibited compression with water, whereas specimens of Calcigel bentonite exhibited swelling. Compression and swelling deformations of the clays with heptane as the inundating liquid remained within about ±1.0% for both clays indicating a very minor interaction between unsaturated clays and molecules of this non-polar organic liquid. The test results emphasized the significance of attractive and repulsive forces and their impact on the volume change behaviour of clays of different mineralogy. [ABSTRACT FROM AUTHOR]

The dynamic characterization of municipal solid waste (MSW), especially in regions with high seismicity, is of considerable importance in the stability assessment of landfills. Additionally, findings indicated that the response of MSW under dynamic loadings is significantly affected by fibrous material. Therefore, a comprehensive strain-controlled cyclic triaxial testing program was performed on MSW samples retrieved from a landfill in the Kahrizak area, Tehran province. The tests were conducted on fresh MSW specimens (with a diameter of 100 mm) with different percentage of fibers in the consolidated undrained condition. The potential reinforcing capability of fibers and their impacts on changes in the MSW composition were investigated under variations of different factors including confining pressure, loading frequency, Poisson’s ratio, and loading cycles. From the results of the study, increasing fiber content in specimens resulted in improved elastic behavior of MSW under dynamic loadings, irrespective of the test conditions, such that the normalized shear modulus reduction curves shifted to the right, while the damping ratio curves exhibited no specific trend. However, it is necessary to simultaneously consider the impact of fiber contents, confining stress and shear strain on the variation rates of normalized shear modulus reduction values. This trend is attributed to the greater values of stiffness from changing the composition when compared with the one generated by obtained reinforcement within the studied strain range. Given the lack of systematic evaluations on the effect of the fibrous waste materials on the dynamic response of MSW, the results of this study provide additional insight into the seismic analysis of landfills. [ABSTRACT FROM AUTHOR]

Soil compaction by machine traffic is a complex process with many interacting factors. The strength of adaptive neuro-fuzzy inference system (ANFIS) is the ability to handle linguistic concepts and find nonlinear relationships between inputs and outputs parameters. In this research, the effect of farmyard manure, the number of tire passes, soil moisture contents and three average depths on clay soil compaction is predicted using ANFIS and Regression. For the prediction of soil compaction, an agricultural tractor tire was used and the experiments were carried out in the controlled condition of soil bin facility utilizing a well-equipped single-wheel tester. To measure soil compaction, cylindrical cores in groups of three were inserted into the three different depths. Various member function ANFIS were tested to discover the supervised ANFIS-based models for the soil compaction. On the basis of statistical performance criteria of MAPE and R 2 , Gaussian curve built-in membership function (gaussmf) was found as a proper model. In addition, the ANFIS model with ‘Gaussian mf’ is recommended considering the higher prediction performance values of MAPE = 0.2957%. The regression analyses of ANFI and Multiple Linear Regression (MLR) revealed a high correlation with farmyard manure, the number of tire passes, soil moisture, and depth. Also, it showed a higher performance compared to the regression model for predicting soil compaction. Thus, it can be concluded that ANFIS-based methodology is a soft computing approach that provides excellent nonlinear systems such as soil compaction. [ABSTRACT FROM AUTHOR]

Elasticity modulus ( E s ) is used to predict the elastic settlement of foundations. Plate load test ( PLT ) is one of the most commonly applied methods to determine this parameter. Given that the method is relatively costly and time-consuming, especially in depths, various empirical equations have been proposed to relate the E s to the results of standard penetration test ( SPT ) which is one of the most frequently used tests during the geotechnical investigation. Considering that the existing relationships are not able to estimate E s properly, in the present research, Group Method of Data Handling ( GMDH ) type neural network ( NN ) is used to estimate the E s of clayey deposits based on a database including 131 plate load test ( PLT ) and standard penetration test ( SPT ) from geotechnical investigation sites in Qazvin, Iran. The comparison between proposed models and existing empirical equations indicate that the GMDH models exhibit higher performance (32–42% improvement) with respect to the other correlations. The sensitivity analysis of the developed models has been conducted to determine the contributions of the parameters affecting E s and shows that N 60 is the most influential parameter on the GMDH -based models to predict E s . Also, it has been demonstrated that the E s predicted by the best model is significantly affected by error in the measurement of the LL value. Therefore, measuring this parameter in the laboratory requires high accuracy. [ABSTRACT FROM AUTHOR]

Spectral induced polarization (SIP) is considered as a promising tool in environmental investigations. However, few works have done regarding the electrical signature of oil contamination of clayey soils upon induced polarization. Laboratory column experiments plus one sandbox experiment are conducted in this study to investigate the performances of the SIP method in oil-contaminated soils. First, a total of 12 soils are investigated to reveal the influences of water and soil properties on the saturation dependence of the complex conductivity below 100 Hz. Results show that the magnitude of the complex conductivity consistently decreases with decreasing water saturation for all soils samples. The saturation n and quadrature conductivity p exponents tend to increase slightly with increasing water salinity when using a linear conductivity model. The saturation exponent increases marginally with the cation exchange capacity (CEC) and the specific surface area ( S sp ) while the quadrature conductivity exponent exhibits a relatively stronger dependence on both CEC and S sp . For the low CEC soil samples (normally ≤10 meq/100 g), the quadrature conductivity exponent p correlates well with the saturation exponent n using the relationship p  =  n −1. SIP method is further applied in a sandbox experiment to estimate the saturation distribution and total volume of the oil. Results demonstrate that the SIP method has a great potential for mapping the organic contaminant plume and quantifying the oil volume. [ABSTRACT FROM AUTHOR]

The achievement of Optimum Compaction Moisture Content (OCMC) of clay soil plays an important role in compaction as well as the durability and strength of compacted soil. This is due to its effect on the structure and orientation of the clay soil particles. Most researchers on stabilised systems involving soils and/or industrial waste by-product additives for applications in roads and buildings are faced with the problem of how to approach the establishment of OCMC, when the complex mixtures involved. This paper reports on the laboratory investigation of theoretical methods of two different approaches to establish the OCMC in the stabilisation of clay soil involving multi-binary binder in cementitious binder system. Furthermore, this research also explores the use of an industrial by-product, Pulverized Fuel Ash (PFA) as partial target material and ground granulated blastfurnace slag (GGBS), with a view to reducing the reliance on the traditional cementitious binders, such as lime and/or Portland Cement (PC), in stabilising Lower Oxford Clay (LOC) soil combining with PFA at 50:50 ratio. LOC + PFA was stabilised both in conventional manner using Lime and PC as control and using sustainable binders incorporating GGBS. The results show that there was no one particular approach to the establishment of the optimal compaction moisture content for best strength development and durability. The best approach being dependent on the period of curing, stabiliser content and whether GGBS was blended with Lime or with PC. Of the various stabilisers studied, the highest strength magnitudes were however recorded with LOC-PFA stabilised using the blended binders incorporating GGBS. For all 7, 28 and 56 days of curing periods, the PC-based stabilisers were observed to be less sensitive to the different approaches to compaction moisture content, relative to the lime-based systems. [ABSTRACT FROM AUTHOR]

This research investigated the feasibility of using a geopolymer based on recycled glass powder (RGP) to improve the mechanical behavior of clay soils. The chemical elements of soil and RGP were determined by XRF. Unconfined compressive strength (UCS) testing was used to investigate the mechanical behavior of specimens. The effects of different parameters, such as the RGP content, molar concentrations, curing time and temperature, were investigated. The results revealed that the UCS and (ε f ) of specimens that were stabilized using a geopolymer were increased in comparison to the unstabilized specimens. SEM-EDX was analyzed to investigate the microstructure of stabilized specimens. [ABSTRACT FROM AUTHOR]

Liquid manure applied on the soil surface may alter its hydraulic conductivity by surface sealing. In this study, we evaluated the chemical and physical mechanisms of the surface sealing process acting in sandy clay loam and clayey soils after liquid manure application (LDM). Factors affecting surface sealing, such as LDM dosage, total solids content of LDM, straw cover, and time after LDM application, were also studied. The saturated hydraulic conductivity (K sat ) was determined before and 24 h and 7 days after LDM application, and the sealing index was calculated. The liquid dairy manure application on the soil surface promoted surface sealing in both soils; around 93% of sealing surface was due to physical mechanisms and around 7% chemical mechanisms. The application of LDM with 9.4% total solids (TS) promoted a greater sealing index (greater surface sealing) compared to LDM with 0% TS, mainly within 24 h of LDM application. Greater surface sealing was also observed with a higher LDM dose (60 m 3  ha −1 ). Soil cover with 5 Mg ha −1 of straw resulted in a lower sealing index (lower surface sealing) than soil with 0 Mg ha −1 of straw. Sealing index was greatest at 24 h after LDM application for all treatments (solids content, LDM dose and soil cover) in both soils (clayey and sandy clay loam). The clayey soil was more susceptible to surface sealing after LDM application than the sandy clay loam. In practical terms, application of LDM with a high total solids content to bare soil when followed by rainfall 24 h after LDM application, enhanced susceptibility to surface sealing and, consequently, greater detrimental effect on surface water quality. [ABSTRACT FROM AUTHOR]

One of the first soil forming processes in marine and fluviatile clay soils is ripening, the irreversible change of physical and chemical soil properties, especially consistency, under influence of air. We used Bayesian binomial logistic regression (BBLR) to update the map showing unripened subsoils for a reclamation area in the west of The Netherlands. Similar to conventional binomial logistic regression (BLR), in BBLR the binary target variable (the subsoil is ripened or unripened) is modelled by a Bernoulli distribution. The logit transform of the `probability of success' parameter of the Bernoulli distribution was modelled as a linear combination of the covariates soil type, freeboard (the desired water level in the ditches, compared to surface level) and mean lowest groundwater table. To capture all available information, Bayesian statistics combines legacy data summarized in a ‘prior’ probability distribution for the regression coefficients with actual observations. Our research focused on quantifying the influence of priors with different information levels, in combination with different sample sizes, on the resulting parameters and maps. We combined subsamples of different size (ranging from 5% to 50% of the original dataset of 676 observations) with priors representing different levels of trust in legacy data and investigated the effect of sample size and prior distribution on map accuracy. The resulting posterior parameter distributions, calculated by Markov chain Monte Carlo simulation, vary in centrality as well as in dispersion, especially for the smaller datasets. More informative priors decreased dispersion and pushed posterior central values towards prior central values. Interestingly, the resulting probability maps were almost similar. However, the associated uncertainty maps were different: a more informative prior decreased prediction uncertainty. When using the ‘overall accuracy’ validation metric, we found an optimal value for the prior information level, indicating that the standard deviation of the legacy data regression parameters should be multiplied by 10. This effect is only detectable for smaller datasets. The Area Under Curve validation statistic did not provide a meaningful optimal multiplier for the standard deviation. Bayesian binomial logistic regression proved to be a flexible mapping tool but the accuracy gain compared to conventional logistic regression was marginal and may not outweigh the extra modelling and computing effort. [ABSTRACT FROM AUTHOR]

Earth-based mortars are commonly reinforced with bio-based materials such as straw or biopolymers. The aim of this work is to identify reinforcements that are able to improve the mechanical strengths and the ductility of an earth-based matrix. We have also attempted to describe the mechanisms of reinforcement involved in such materials. Firstly, a kaolinite-based clay soil was mixed with sand to achieve earth-based mortars with the highest density at the dry state. For this material (kaolinite-based mortar), we have shown that, at the same water content, the compressive strength at the dry state only depends on the dry density of the sample whatever the forming process. Various quantities of fibers, fabrics and alginate were then used to reinforce the studied mortars (a kaolinite based mortar and a natural soil containing swelling clay sieved at 4 mm). We found that these reinforcements significantly increase the compressive strength of all tested samples containing kaolinite. A comparison between the two materials helps us to understand the reinforcement mechanisms for various fibers; it also demonstrates that natural fibers and woven fabrics enhance the mechanical behavior of earth mortars notably under a compressive load. [ABSTRACT FROM AUTHOR]

This paper presents two well-instrumented large-scale field tests of PVD-improved soft soil with vacuum and surcharge preloading, respectively. The two large-scale field tests were conducted adjacent to each other with the same preload. A comparative analysis was performed to investigate the performance of subsoil (i.e., the ground settlement, the layered settlement, the lateral displacement of subsoil and pore water pressure) under vacuum preloading and equivalent surcharge preloading. Some design methods were verified based on the field data. Cone Penetration Tests (CPT) and Vane Shear Tests (VST) were conducted to assess the improvement effects on subsoil after preloading. The results showed that as compared with surcharge preloading, vacuum preloading mitigated the differential settlement of the ground. The vacuum pressure transmitted into the soil with a minor loss through the PVD length. From a practical point of view, the improvement effects by vacuum preloading and surcharge preloading were similar in terms of influence depth and soil strength based on the in-situ tests. [ABSTRACT FROM AUTHOR]

• MSW composts at 40 Mg ha−1 favoured alfalfa growth grown in clay and sandy soils salt stress decreases the alfalfa growth, and is more pronounced in sandy soil. • Compost amendment with salt supply increased dry alfalfa shoots. Plant production is higher in clay soils. • MSW compost partially compensates the effect of salinity on plant growth and nutrient uptake. • MSW compost amended at rates of 40 Mg ha−1 increase heavy metal phytoavailability, although below phytotoxic level. • Alfalfa is a solution to use salted water or restore soils affected with salinization. The availability of water resources of marginal quality such as drainage water or high-salt containing groundwater is turning into an important issue in Tunisia and other countries with scarce water resources. A pot experiment was carried out to evaluate plant production, nutrient content and heavy metal bioaccumulation in agricultural soils amended with MSW compost and irrigated with salty water, by using two different soil textures (clay and sandy). Salt water supply decreased plant dry yield in both soils. Salt stress had significantly reduction in plant biomass in sandy soil compared to those in clay soil (biomass of dry weight is significantly higher in clay soil than those in sandy soil in presence of salt: percentage of growth compared to control was 55% for clay soil and 45% for sandy soil). The application of Municipal Solid Wastes (MSW) Compost increased significantly alfalfa productivity in both soils (Dry weight is significantly higher in presence of compost: 140% for clay soil and 125% for sandy soil). In non-amended soil, the growth was reduced significantly by salt stress (50% in clay soil, 26% in sandy compared to the soils without salty water application). Plants irrigated with salty water accumulated much more sodium on sandy soil (1.74 mmol g−1) than on clay one (0.87 mmol g−1 DW). Compost did not reduce sodium accumulation in aerial parts on sandy soil, whereas it slightly reduced it in those grown on clay soil. Zinc (Zn), Copper (Cu), Lead (Pb) and Cadmium (Cd) concentrations showed the same trend for both soil types. They increased statistically significant by salinity to 124–189%, the highest rise was found in Cu concentration on clay soil. The order of metal uptake was: Zn > Cu > Pb > Cd. A higher significant shoot accumulation of heavy metals (up to 305% of the control) was noticed in the presence of compost with no difference between salt-treated and non-treated. MSW compost amendment caused an increase of the studied heavy metals in alfalfa shoots grown that was higher on sandy soils than clay soils. Heavy metals in plants remained lower than phytotoxic level and these level of accumulation did not restrain the enhancement of alfalfa yield. MSW compost at 40 t ha−1 was convinent to do not attend phytotoxic level. These results suggest that MSW compost compensates, at least partially, the negative effect of salinity on plant growth and nutrient uptake and that it is important to know soil texture to apply compost to remediate salty degraded soils. [ABSTRACT FROM AUTHOR]

Serpentinites occur worldwide in various geological settings, such as in magma-starved oceanic basins. Abyssal serpentinites are long-term storage for chlorine and carbon, the latter forming dominantly reduced and subordinately oxidized compounds. Hence, serpentinites, salts, and reduced carbon phases coexist in an “abyssal association”. Although huge reservoirs of salts and reduced carbonaceous matter in abyssal serpentinites are thought to be lacking, this may be more a reflection of intrinsic limits in research methods than an indication of their absence. On the other hand, shallow-seated hydrocarbon-rich mud volcanoes and diapirs, consisting of salts, hydrocarbons (oils and gases), and clayey muds (including mudded serpentines) can provide evidence for such an oceanic association. Here, we search for scientific data in support of the “oceanic association”, and hence we propose a reappraisal of exploitable worldwide salt-hydrocarbon reservoirs, even gigantic in size. Abyssal serpentinites are well-known source rocks of abiotic gaseous hydrocarbons via Fischer-Tropsch-type reaction (FTT), whereas macromolecular carbonaceous matter (mostly bitumen) found in serpentinites is postulated to be biogenic. This inference is based mainly on three assumptions: (i) FTT in nature does not yield oils; (ii) hydrocarbons derive essentially from the thermal alteration of microbial molecules; (iii) the presence of biomarkers, traditionally considered evidence of the biological origin of oils. Nevertheless, some lines of strong evidence disprove these accepted conventions: (i) Lab experiments demonstrated that FTT can synthesize significant quantities of liquid hydrocarbons (oils) under conditions compatible with the deeper and more reduced level of serpentinite-hosted hydrothermal systems; (ii) macromolecules, generally thought to derive from microbial activity, can be abiotically generated as documented in extraterrestrial bodies; (iii) biomarkers are evidence for the proliferation of microbial communities, which subsist on serpentinization and FTT products, thus they are biological pollutants. Moreover, seawater-driven serpentinization consumes water producing huge amounts (∼11 kg halite·m −3 of peridotite) of salts that can be stored in the deeper zone of abyssal-type hydrothermal systems. Thus, the origin of shallow-sited salt deposits, even gigantic in size, can be related to either the advective upwelling of hot hydrothermal brines, due to the dehydration of abyssal serpentinites, or to the passive upwelling of buoyant saline geobodies. Piercement structures are indeed seismically imaged in several localities, such as South Atlantic, the Gulf of Mexico, the Serpentinite belt extending from Cuba to Hispaniola, the North Sea trench, and the Zagros orogenic belt. Similar lines of evidence at the microscopic scale have been found in some Hyblean serpentinite xenoliths (south-eastern Sicily), being representative of the unmetamorfosed in-situ relic of the Palaeo-Tethys Ocean, upon which Sicily and its off-shore areas lie. In spite of the accepted stereotype of hydrocarbons as fossil fuels, and hence finite resources, reduced carbon compounds abiotically produced in abyssal serpentinites may be copious, protracted over time, and thus renewable. [ABSTRACT FROM AUTHOR]

In this paper we propose a new nonlinear elasto-viscoplastic damage model, based on a modified Mohr-Coulomb criterion, to study the creep and seepage in clayey rock during construction of a high-level radioactive waste repository through laboratory experiments and field tests. First, three types of damage evolution equations are constructed by using the relationship between the damage variable and the strain. Then, a self-healing model is investigated for the clayey rock by considering the damage, confining pressure, pore water, and duration of saturated state. By introducing the damage, permeability evolution and self-healing as the key factors, a fully coupled hydro-mechanical model for clayey rock is developed with the commercial software ABAQUS. The hydro-mechanical behaviour in the surrounding rock is simulated with the proposed model considering the actual construction of the repository. The numerical results show that the construction quality has a significant effect on the stability of the rock formation, and that the extent of the horizontal gallery disturbed by shield tunnelling is less than that of the test drift disturbed by using jackhammers method. The creep damage of the surrounding rock increases rapidly at the early stage and tends to stabilize gradually after 15 years, and the damage in the middle part of the surrounding rock is larger than that in the bottom and top parts. In addition, due to the self-healing effect of clayey rock, around three years later, the permeability of the excavation disturbed zone (EDZ) is close to that of the original clayey rock with an order of magnitude 10 −19 m 2 . The present model can also be used to predict the long-term stability of tunnels. [ABSTRACT FROM AUTHOR]

Moringa oleifera Lam. and Ricinus communis L. are species known for their ability to survive in different environments; however, analyses of their capabilities to develop and explore clayed compacted soils are still not well covered. This study compares above- and below-ground development of Ricinus and Moringa in a subtropical compacted clayey soil. Seedlings of each species were germinated and monitored in field conditions during 12 months. After this period, 10 plants of each species were excavated to measure shoot versus root data along the soil profile. With the correlated data, we developed a model for each species to estimate root biomass and volume distribution. Results showed that Ricinus became a mature plant in a quarter of time than Moringa , but Moringa had 18% higher survival rate. Root volume distribution of both species was fitted by logistic and exponential models with 90% of their volume within the first 40 cm 3 around the tap root. Average lateral root inclination was −22° for Moringa and −36° for Ricinus . Root volume in Moringa was 5.5 times higher than that of Ricinus . The product of stem base by the crown-width for Moringa and stem base by plant-height for Ricinus were the best estimators (R 2  > 0.9) for below-ground biomass. We conclude that both species were capable to grow and reproduce in a clayey and compacted soil; nevertheless, Ricinus developed 16% more oblique and sinker roots to maintain its denser crown, while Moringa took advantage of the mass of its dense trunk and roots for a shallower exploration. [ABSTRACT FROM AUTHOR]

The threshold yield stress plays a key role in controlling the rheological consolidation behaviour of soft clay. A semi-analytical theory combining numerical and analytical methods is introduced that excludes the effects of clay self-weight. The governing equations assume the clay is an elasto-viscoplastic material. Approximate solutions as well as computational programme to surface loading for two drainage boundary conditions are obtained, while the clay profile is separated into material which is overconsolidated and normally consolidated. The effects of threshold yield stress and time-dependent loading on the rheological behaviour of soft clays are explored using the solutions developed. [ABSTRACT FROM AUTHOR]

Since the discovery of oil and gas in Oloibiri, an onshore oilfield located in Oloibiri in Ogbia Local Government Area of Bayelsa State, Nigeria on Sunday 15th January 1956 by Shell Darcy, hundreds of oil wells have been drilled and not a single of these oil wells was drilled without the use of bentonite. This work is aimed at evaluating the rheological properties of raw and beneficiated Nigerian clays to ascertain their worth for use as drilling mud in oil and gas well drilling. This will save foreign earnings used in the importation of bentonite by the oil and gas development companies, create employment opportunity and open a new frontier for solid mineral development. Five clay samples from Pindiga Formation in Benue Trough, northeastern Nigeria were collected and subjected to elemental, rheological and other physical properties tests and analysis, while another portion of same samples were beneficiated using sodium carbonate, gum Arabic and poly-anionic cellulose for rheological enhancement then subjected to same cycle of tests and analysis above. Results obtained indicates that wet beneficiation as adopted in this study has proved to be more effective in Ca and Na ionic exchange. The rheological and other physical properties of the clays attained the standard that is required for use in oil and gas well drilling after addition of 12% sodium carbonate and 1.5 g poly-anionic cellulose. It was also discovered that when the formulation was allow to age (stay for 24 h), it attained optimum rheological requirement with 12% sodium carbonate and just 0.8 g poly-anionic cellulose. The clays studies do not require addition of weighing additive such as barite because of their high iron content which made their density attain the require standard even without additives. [ABSTRACT FROM AUTHOR]

Long-term low cyclic loads are often encountered in marine environment, but the cyclic behavior of soil under this loading condition is rarely studied. Undrained pore pressure behavior of soft marine clay subjected to long-term low cyclic loading is of considerable importance for the proper design and maintenance planning of foundations of near- and off-shore structures. In this paper, a new hyperbolic model is proposed to predict the development of undrained pore pressure. This model is verified by experimental data from literature. Compared with the existing models, the proposed model has better capability and performance. With use of the proposed model, a hyperbolic relationship between cumulative plastic strain and pore pressure was derived and verified by experimental data. Finally, the effects of cyclic stress ratio, confining pressure and loading frequency on pore pressure are investigated. In summary, this work provides a novel model and some innovative observations to better understanding undrained pore pressure behavior of soft marine clay under long-term low cyclic loads. [ABSTRACT FROM AUTHOR]

The piled-raft foundation is usually adopted to support the offshore structures. In the present study, a large piled-raft has been simulated numerically through 3-D finite element modeling. The objective of the present study was to investigate the effect of pile spacing, pile length, pile diameter and raft-soil stiffness ratio on the settlement, load-sharing, bending moments, and shear force behavior of large piled-raft foundation. The results indicated that with increase in pile spacing up to the 5 to 6 times of the pile diameter, both average settlement ratio and differential settlement ratio decreased effectively and thereafter it increased gradually. Raft with smaller raft-soil stiffness ratio and larger pile group to raft width ratio observed to be effective in decreasing the average settlement ratio. The load-sharing ratio decreased with increase in pile spacing whereas; it increased with increase in pile length. With increase in pile spacing, bending moment ratio increased and as the length of pile increased bending moment ratio decreased up to pile group to raft width ratio of 0.6 and thereafter it increased. [ABSTRACT FROM AUTHOR]

Dispersive soils are clayey, high in sodium content, and washed easily when subjected to water with low salt concentrations. The works of stabilizing dispersive soils using chemical additives from throughout the world are well documented. In the current study, a highly dispersive clay was treated with various proportions of lignosulfonate, an environmentally friendly stabilizer. A 58% reduction in dispersivity of the soil was achieved by addition of 1.5% lignosulfonate by dry mass. Meanwhile, the electroosmosis technique is known as an effective and modern soil improvement method. In the subsequent stage of the study, the effects of electroosmosis treatment on the dispersive clay were investigated by using different potentials. The dispersivity of soils taken from around the anodes was found decreased by 52% after 7 days of electroosmosis application under 48 V potential. The above two methods were capable of reducing dispersivity however, when used alone, insufficient in bringing the treated soils into the non-dispersive category. Consequently, the simultaneous treatment by lignosulfonate addition and electroosmosis application was successful in reducing the dispersivity of the initially highly dispersive clay by 65% and qualifying it for the non-dispersive designation. [ABSTRACT FROM AUTHOR]

Desiccation cracking process negatively impacts both mechanical and hydraulic properties of clayey soils. Traditional methods applied for the characterization of soil cracking behaviors are mainly based on visual inspections or destructive approaches. The electrical resistivity method provides a non-destructive, sensitive and continuous evaluation of the spatiotemporal variations of many soil physical properties. In this study, an integrated experimental setup is configured to simultaneously capture the evolution of temperature, relative humidity, water content, crack morphology, and apparent electrical resistivity in clay during continuous drying. Apparent electrical resistivity measurements at 1.0 cm electrode spacing are carried out to detect the initiation, propagation and coalescence of desiccation cracks. Image processing quantitatively describes the geometrical characteristics of shrinkage surface crack patterns. Experimental results indicate the strong correlation between the measured apparent electrical resistivity and cracking behavior of soil. As water content decreases during drying, the apparent electrical resistivity of initially saturated clayey soil decreases first before the onset of desiccation cracking, and then transits into the increasing trend. The evolution of apparent electrical resistivity in clayey soil is dominated by two competing effects, with one originated from the volumetric shrinkage-induced closer packing of soil fabric and higher concentration of ions in pore fluids, and another from the evaporation-induced water loss associated with hydration film contraction and desiccation crack insulation. The electrical resistivity method is an effective technique to characterize the development of desiccation cracks, and particularly reliable to map their positions. This study is expected to improve the fundamental understanding of desiccation cracking mechanisms in soils and provide insights on soil characterizations for enhanced stability and performance of earthwork structures. [ABSTRACT FROM AUTHOR]

This study evaluates the characteristics of soil seed bank in two types of central African rainforests: Celtis forest on clay soils and Manilkara forest on sandy soils. In each study site, 30 samples were collected per soil layers (litter, 0–5 cm, 5–10 cm and 10–20 cm depth). The species diversity and abundance of the soil seed bank were estimated after soil samples were brought to germination. We globally observed 297 seedlings of 53 species for the Celtis forest and 222 seedlings of 39 species for the Manilkara forest. The total densities of germinated seeds were 330 seedlings m −2 and 247 seedlings m −2 , respectively. Herbaceous species dominated with percentages of 41.0 and 45.3%, respectively in the Manilkara forest and the Celtis forest. Both forest types displayed a regeneration potential through the soil seed bank. However, this potential seems higher in the Celtis forest. Pioneer taxa were more abundant in the soil seed bank of the Celtis forest (13 woody pioneer species) than the Manilkara forest (9 woody pioneer species). The values of Sorensen similarity index between the standing tree vegetation and the soil seed bank in each site were relatively low: 11.0% for the Celtis forest and 8.8% for the Manilkara forest. But these similarity values were higher when only the pioneer species were considered: 46.8% in the Celtis forest and 38.9% in the Manilkara forest. The highest species richness were obtained in the first two soil layers (0–10 cm depth) while 21.8% and 21.4% of the species were exclusively found in the deepest layer (10–20 cm) in the Celtis forest and the Manilkara forest, respectively. Among the timber species found in the forest, only three were observed in the soil seed bank of the two sites: Nauclea diderrichii , Erythrophleum suaveolens and Staudtia kamerunensis . N . diderrichii was particularly abundant in the soil seed stock of the two sites (14.4–34.4 seeds m −2 ). Results suggested that to improve regeneration of timber species, planting in open forest habitats with seedlings coming from tree nursery should be more efficient. [ABSTRACT FROM AUTHOR]

Using a ring shear apparatus, the variation in the residual strength characteristics of 21 groups of saturated clay soil samples were experimentally investigated, and the results are discussed in this paper. The clay soil samples had different plasticity indexes under 10 different consolidation conditions. The influences of shear rate, over-consolidation ratio, plasticity index, and multi-stage shear mode on the residual strength were investigated. New shear strength variation trend data and a corresponding equation for shear strength calculations as a function of plasticity index of soils under large deformation are presented. The experimental results indicate that 1) both the shear rate and over-consolidation ratio have a negligible influence on the residual strength; 2) the residual strength gradually decreases as the plasticity index increases; 3) the residual strength shows a significant nonlinearity with the normal stress when subjected to low- or high-levels of normal stress; 4) the internal friction angle of drained clay decreases as the plasticity index increases under large deformation. Finally, a formula is proposed to describe the relationship between the residual inner friction angle and plasticity index. [ABSTRACT FROM AUTHOR]

This study investigated the potential of using water reducer (WR) to enhance the mechanical and durability properties of cement-treated soil. WRs have long been used in Portland cement concrete (PCC) to increase the properties of PCC. When added at a small dosage, WR helps improve the dispersion of cement particles and release the water otherwise entrapped in cement clusters, thus reducing the water demand for the same consistency or increase the consistency of PCC without adding more water. Cement-treated soil uses similar raw materials and has similar chemical compositions to PCC. However, little research has been conducted to explore the potential of using WR in cement-treated soil to improve its compaction and thus its mechanical and durability properties. In this study, a laboratory experiment was conducted to examine the effects of WR on the compaction characteristics and engineering properties of cement-treated soil. As expected, similar benefits of water reduction and improved properties could be achieved by adding WR in cement-treated soil. The improved mechanical and durability properties of cement-treated soil were due to the fact that WR could improve the compaction behavior of cement-treated soil through reduced optimum moisture content and increased maximum dry density. Further studies are recommended for the interaction among WR, soil particles, and cement particles to achieve an optimal effect for engineering applications. [ABSTRACT FROM AUTHOR]

We present a contextual spatial modelling (CSM) framework, as a methodology for multiscale, hierarchical mapping and analysis. The aim is to propose and evaluate a practical method that can account for the complex interactions of environmental covariates across multiple scales and their influence on soil formation. Here we derived common terrain attributes from multiscale versions of a DEM based on up-sampled octaves of the Gaussian pyramid. Because the CSM approach is based on a relatively small set of scales and terrain attributes it is efficient, and depending on the regression algorithm and the covariates used in the modelling, the results can be interpreted in terms of soil formation. Cross-validation coefficient of determination modelling (R 2 ), for predictions of clay and silt increased from 0.38 and 0.16 when using the covariates derived at the original DEM resolution to 0.68 and 0.63, respectively, when using CSM. These results are similar to those achieved with the hyperscale covariates of ConMap and ConStat. As with these hyperscale covariates, the multiscale covariates derived from the Gaussian scale space in CSM capture the observed spatial dependencies and interactions of the landscape and soil. However, some advantages of CSM approach compared to ConMap and ConStat are i) a reduced set of scales that still manage to represent the entire extent of the range of scales, ii) a reduced set of attributes at each scale, iii) more efficient computation, and iv) better interpretability of the important covariates used in the modelling and thus of the factors that affect soil formation. [ABSTRACT FROM AUTHOR]

To increase the analytical precision in identifying structural forms of heavy metals, it is necessary to refine the methodology for analysis of mineral crystals. The aim of this study was to characterize clay crystals in soils, and relate their mineralogy to the structural occurrence of Pb using scanning transmission electron microscopy (STEM) together with energy dispersive X-ray (EDX) spectrometry. We sampled soils from two areas naturally rich in heavy metals, with known occurrences of mineral deposits (PbS) in carbonate and phyllite/mica schist rocks. There was an association of P with Pb, and the main mineral phase containing Pb in the soil clay fractions was plumbogummite. No associations between Pb and Fe oxides were observed. Secondary phyllosilicate minerals, such as kaolinite and smectite, did not contain structural Pb. There was isomorphous substitution of Ti by Pb in an anatase crystal, despite the differences in ionic radii. The chemical analysis of individual crystals by STEM-EDX was hampered by the high occurrence of microaggregates of clay minerals. [ABSTRACT FROM AUTHOR]

The behaviour of two sections of a test embankment constructed in Ballina, Australia, was predicted by finite element analyses before (Class-A) and after (Class-C) knowing the field-measured data. By comparing the predictions with the field data, it is concluded that simple models such as modified Cam clay, with reliable values of model parameters, can produce reasonable results for the performance of embankments on clayey deposit improved through prefabricated vertical drains for a relatively short time period. The Class-A prediction is judged as reasonably good, and the Class-C prediction gives satisfactory simulations of the field performance. [ABSTRACT FROM AUTHOR]

This paper presents field test data from four instrumented rigid square pad foundations on soft clay that were brought to failure under concentric vertical loading. The test programme comprised two unconsolidated undrained (UU) foundation tests as well as two consolidated undrained (CU) tests. In the latter case the two foundations were preloaded to a proportion of the UU capacity and the soil was allowed to consolidate before being brought to undrained failure. In this paper, the site works and testing procedures are presented along with the load- and time-settlement responses of all four foundations. Horizontal stress and pore pressure data are presented for the two CU tests. The undrained and consolidated undrained load-settlement responses are shown to agree well with theoretical and numerical predictions. Results from the UU tests were the subject of a prediction exercise, summarised in a companion paper presented in this special issue. [ABSTRACT FROM AUTHOR]

This paper presents Class-A and Class-C predictions of the behaviour of an embankment built on soft Ballina clay improved with prefabricated vertical drains. Predictions were carried out using hand calculations and the finite-difference method. The latter approach allowed the variation of soil parameters and stress levels with depth to be considered in the analyses. An alternative systematic procedure for estimating soil parameters based on high-quality laboratory data is described. Class-A predictions highlighted some disagreements with the measured total settlements and pore pressure dissipation rates. For Class-C predictions, the choice of geotechnical parameters used in the analyses was guided by a systematic assessment of the stress states undergone by soil elements underneath the embankment centreline. This led to a better agreement between predicted and measured data, which demonstrates the potential of the proposed procedure for future analyses of embankment behaviour on soft Ballina clay. [ABSTRACT FROM AUTHOR]

A test embankment was established on the soft Ballina clay and practising engineers and academics were invited to make predictions of the behaviour of the embankment. Comprehensive geotechnical investigations were performed and the testing data were provided to the predictors. This paper presents Class A and Class C predictions made by the authors for the embankment. In Class A prediction, the soft clay was modelled as a single homogeneous layer. The Class A prediction showed good agreement with measurements for settlement, but not for pore pressure and lateral ground movement. Class C prediction divided the soft clay into two layers based on the information of ground investigation, and achieved better predictions for settlement, pore pressure and lateral movement. Finite element analysis using Plaxis 2D was carried out for the prediction, and Soft Soil Creep model was used for the soft clay. Consolidation parameters were assessed by statistical analysis of the oedometer test data. Sensitivity studies were performed to investigate the influence of parameters on the analysis results. Results of the predictions and sensitivity studies are discussed in the paper. [ABSTRACT FROM AUTHOR]

A model prediction using FE modeling is performed for a trial embankment on soft clay in Ballina, Australia. The comparison between the prediction and the in situ measurement exhibits significant differences. A detailed analysis is performed to validate the model and determine necessary improvements. Sensitivity analyses elaborate upon the most dominant constitutive parameters. Based on site measurements, inverse analyses are performed to identify the optimum parameters. The inverse analysis approach is validated regarding its dependency on the objective function and data incorporated. A comparison between the prediction and the back-calculated parameters confirms the importance of engineering judgment as well as the sensitivity of the modeling strategies to the input information. [ABSTRACT FROM AUTHOR]

The paper summarises key results of a class A prediction obtained from 2D and 3D finite element analyses performed for the Embankment Prediction Symposium 2016. In addition class C predictions are included and the changes in input parameters for the finite element model are discussed. Although different constitutive models have been employed in the class A prediction where short term displacements, i.e. after embankment construction, have been considered in addition to long term consolidation and creep settlements only long term displacements are dealt with in this paper. Thus, only results obtained with the Soft Soil Creep model implemented in the finite element code Plaxis are presented. Input parameters have been chosen based on laboratory and in situ experiments and verified by back calculation of undrained triaxial tests and CRS tests. 3D FEA have been carried out confirming that a 2D representation is sufficient for this problem. [ABSTRACT FROM AUTHOR]