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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]

Three quarters of the world's significant urban centers are located in coastal regions where clay minerals are prevalent. The microstructures and physico-mechanical properties of clay sediments are highly susceptible to alterations in pore water chemistry. The pore water chemistry in soil changes easily due to groundwater pollution, seawater erosion, degradation, etc. However, there are several inconsistencies in the literature on the change of physical and mechanical properties of clay soils caused by the change of pore water chemical properties, i.e., disparate experimental results were reported for the same soil property, or varying explanations were proposed for the identical experimental results. Currently, the research in this field mainly focuses on the macroscopic behavioral modifications while lacking the explanations of microscopic mechanism. Therefore, this paper presents a comprehensive review of researches conducted over the past four decades on the impact of pore water chemistry (including salt type, salinity, ion valence, pH) on soil properties such as the microstructure, settlement, Atterberg limits, shear strength, conductivity, unsaturated soil mechanics properties and thermal properties. The fundamental mechanisms underlying the varied experimental observations on clay sediments affected by salt and pH are systematically explored, and deficiencies in this field are identified. The observed dispersion in the literatures is attributed to the spatial variation and heterogeneity of soil compositions, different test methods, and insufficiency of the fundamental microscopic mechanisms of the observed soil behaviors, etc. Therefore, it is necessary to further explore the essential mechanisms of the test results in the future to establish a unified conclusion. [ABSTRACT FROM AUTHOR]

This investigation examines the effect of clamshell ash (CSA) and lime additives on the physico-mechanical characteristics of kaolinite clay soil stabilized at the optimum silica fume content. Laboratory tests were performed to assess plasticity, shrink-swell characteristics, compaction characteristics, unconfined compressive strength (UCS), shear strength characteristics, mineralogical and morphological microstructure characteristics of stabilized soil specimens. The kaolinite clay soil was stabilized at its optimum silica fume content (6%) to produce the highest strength and was altered with three non-identical proportions of clamshell ash and lime (3%-9%). Cylindrical soil specimens, 76 mm in height and 38 mm in diameter, were moulded and treated for curing periods of 1, 7, 14, and 30 days to examine the strength of the altered soil. The findings revealed that, adding clamshell ash and lime significantly alters the plasticity, shrink-swell, maximum dry unit weights, and optimum moisture contents of the silica fume-stabilized soil. In terms of strength, the beneficial effects of CSA and lime additives were found to be more significant with more extended curing periods. Incremental increases in curing periods resulted in further enhancements in UCS, cohesion, and internal friction angle, indicating continued strength development over time. Microstructural analysis using field emission scanning electron microscopy and X-ray diffraction provided insights into the interparticle bonding mechanisms and microstructural changes induced by the addition of CSA and lime. The emergence of cementitious phases and pozzolanic responses between soil particles and stabilizers contributed to the densification and strengthening of the stabilized soil matrix. The findings of this study provide valuable insights into the potential of clamshell ash and lime additives to enhance the engineering properties of kaolinite clay soil stabilized with silica fume. These results have implications for sustainable soil stabilization practices, offering a promising approach to improve the performance of soils for various engineering applications, including construction and geotechnical projects. [ABSTRACT FROM AUTHOR]

Laboratory experiments on clayey soils under dynamic triaxial compression were conducted to establish a nonlinear relationship between the dynamic modulus of soil deformation and the frequency of impact. The most significant increase in the dynamic modulus of soil deformation is observed under an increase in frequency from 5 to 10 Hz. In comparison with fluvioglacial soils, the dynamic deformation modulus in glacial loams grows slower under an increase in frequency. This confirms the dependence of the obtained relations on the genesis of soils. The research results were used to develop vibration protection systems for high-precision equipment in high-tech industries. [ABSTRACT FROM AUTHOR]

Identifying strength parameters under drained conditions is crucial for monitoring and evaluating long-term soil deformations caused by structures built on or in soils. Geotechnical engineers carry out direct shear tests (DSTs) and triaxial tests (TAs) in the laboratory to identify strength parameters under such conditions. However, it can take considerable time to ascertain the failure envelope of even a single soil in the TA tests commonly used to evaluate drained conditions. This study explores whether the effective internal friction angle (ϕ′)—as one of the drained shear strength parameters of remolded soils—can be identified with a vane shear test (VST) at very low (down to 0.001/min) rotation speeds, which is easy to implement and takes a relatively shorter time. For this aim, 18 different remolded soil samples with a wide range of plasticity were prepared using static compaction in the laboratory. DST tests were conducted under drained conditions to evaluate the drained shear strengths of the remolded soil samples. VST results indicate that the peak shear strength decreases with the rotation speed as expected. Shear strengths obtained from the slowest VSTs were correlated with ϕ′s from DSTs. While the results were not encouraging, it was observed that the results of VSTs still could be used in a predictive equation for ϕ′ which, as a function of LL and total density as well as VST strength parameter, the regression coefficient rose to 0.92. Some effective cohesion intercepts were observed during DSTs, which in turn somewhat reduce the predicted ϕ′s. [ABSTRACT FROM AUTHOR]

Clayey soils exhibit significant volumetric changes in response to variations in water content. The swelling pressure of clayey soils is a critical parameter for evaluating the stability and performance of structures built on them, facilitating the development of appropriate design methodologies and mitigation strategies to ensure their long-term integrity and safety. We present a dataset comprising maximum swelling pressure values from 759 compacted soil samples, compiled from 16 articles published between 1994 and 2022. The dataset is classified into two main groups: 463 samples of natural clays and 296 samples of bentonite and bentonite mixtures, providing data on various types of soils and their properties. Different swelling test methods, including zero swelling, swell consolidation, restrained swell, double oedometer, free swelling, constant volume oedometer, UPC isochoric cell, isochoric oedometer and consolidometer, were employed to measure the maximum swelling pressure. The comprehensive nature of the dataset enhances its applicability for geotechnical projects. The dataset is a valuable resource for understanding the complex interactions between soil properties and swelling behavior, contributing to advancements in soil mechanics and geotechnical engineering. [ABSTRACT FROM AUTHOR]

Discrete measurement targets were frequently utilized in image-based methods on the specimen's surface to monitor the soil specimen during triaxial testing. However, the required density of measurement targets that should be used in triaxial testing to achieve highly accurate volume measurement has not been investigated. To overcome this limitation, this paper presents a parametric study to determine the optimum target/point densities to be utilized on the triaxial soil specimen surface to achieve the desired level of volume measurement accuracy in image-based methods. LiDAR scanning was applied to establish the "ground truth" volume of the specimen. The effects of deformation and failure modes were investigated by calculating the volume measurement accuracy at different strain levels and for different undisturbed soil specimens of clay and sand with silt. An interpolation method was proposed to increase the number of discrete targets representing the triaxial specimen's surface. The analysis results show that a higher target density is required at a larger strain. Also, adding the number of interpolation points can only increase the accuracy to a certain level. As the volume measurement accuracy was different for each of the clay and sand with silt specimens, the non-uniform deformation, and failure mode of the specimen can affect the required optimum density of discrete measurement targets. In conclusion, it is recommended to choose the optimum density of targets based on the accuracy requirement, the maximum soil deformation level, and the expected failure mode of the specimen. [ABSTRACT FROM AUTHOR]

Expansive soils, characterized by their propensity to undergo volume changes in response to moisture variations, pose significant challenges to civil engineering due to the presence of the montmorillonite mineral. This mineral exhibits a high capacity for water absorption, leading to volumetric expansion and consequent soil heave. This study aims to provide a comprehensive understanding of the behavior of expansive soils, focusing on variations induced by different proportions of bentonite enrichment. In this research, both experimental and theoretical approaches are employed. Experimentally, the swell percentage, liquid limit, plastic limit, shrinkage limit, maximum dry density, and optimum moisture content are determined for three bentonite-enriched soil samples: clay with 40%, 60%, and 80% bentonite. Theoretically, the validity of existing empirical equations is assessed in light of the experimentally observed behavior of the bentonite-enriched soils. This dual approach allows for a nuanced understanding of the behavior of expansive soils and provides a foundation for the development of more accurate predictive models. Through this integrated analysis, this study contributes to the body of knowledge on the impact of expansive soils on civil engineering structures and offers a pathway towards more effective management of these challenges. [ABSTRACT FROM AUTHOR]

Troublesome events are related to the stabilisation of sulfate-rich soils with calcium-based materials. To overcome these inconveniences, research studies have been conducted applying modified and alternative treatments to soils containing low and high sulfate levels. This paper intends to assess the effects of mellowing period (MP) (2 and 4 days), Portland cement content (5%, 7% and 9%), density (15.75, 16.60 and 17.50 kN/m3) and curing time (14 and 28 days) on the performance of a clayey soil from the Paraguayan Chaco region containing high amounts of sulfates. A complete factorial design set was carried out to assess the unconfined compressive strength (UCS) and the one-dimensional free vertical swelling of compacted soil–cement–lime mixtures. The results showed a positive effect of the MP relative to the swelling of the stabilised soil. In addition, the curing period, the amount of cement and the dry unit weight were the most influential factors regarding the UCS. The stabilisation method addressed in this research – that is, extended mellowing combined with lime and Portland cement, seems to be of great importance for practical purposes on the stabilisation of soils containing high amounts of sulfates. [ABSTRACT FROM AUTHOR]

Expansive soils are extremely susceptible to swelling and shrinkage associated with seasonal changes in their moisture content. This can cause serious damage to structures constructed on expansive soils. Stabilization using additives is widely used to mitigate the concerns of expansive soils by controlling the changes in volume, thereby increasing the strength and durability of the soils. Multistabilizers, including a low percentage of conventional additives with nonconventional additives, can reduce the costs of stabilization. The performance of the stabilized soil can be enhanced by admixture optimization to ascertain that the agent's ratios are quite adequate to meet the optimal levels of modification. Unfortunately, despite the development of advanced techniques for investigating the stabilization of expansive soil, limited studies are devoted to the optimization of admixture to soils. Hence, in this research, an approach based on rough set theory, a mathematical data mining approach, is presented for multiagent optimization for efficient treatment of expansive soils. The multiadditives used in this study are almond shell ash (ASA), volcanic rock dust (VRD), and portland cement (PC). The differential free swell test, the California bearing ratio test, and the unconfined compressive strength test were applied for assessing the characteristics of the stabilized soil specimens. The obtained results and the confirmatory tests demonstrated that a combination of 20% ASA and 20% VRD with 8% PC provides the optimum results in the properties of expansive soil. The microstructural analysis denoted an enhanced modification of the soil engineering properties. The outcomes of this research confirm that the rough set optimization procedure is highly suitable for application in multiagent optimization for the efficient treatment of expansive soils. [ABSTRACT FROM AUTHOR]

A method for an a priori estimation of the frost heave ratio for clayey soils, considering the degree of their water saturation upon a closed system of freezing, is proposed. The proposed approach involves the introduction of a new parameter in the mechanics of frozen soils, namely, the frost heave index of clayey soils, which characterizes the degree of frost heaving of soil relative to the maximum height of the frost heave of soil that is fully saturated with water. An introduced parameter is used in the final formula to estimate the frost heave ratio of clayey soils. Laboratory experiments were performed to determine the height of frost heaving of clayey soils with a variation in their moisture and porosity to verify the proposed approach. A comparison of the experimental and calculated results showed a suitable convergence sufficient for the practical use of the formula to determine the frost heave ratio in a closed system of freezing. An example of a calculation to justify antiheaving measures using the proposed estimation of the frost heave ratio is given. [ABSTRACT FROM AUTHOR]

Newly, the utilization of polypropene for packaging consumer products was populated significantly, which might make ecological problems. Hence, it is substantial to detect environmentally friendly techniques to recycle these waste substances without causing any environmental risks. One such technique could be the utilize poly wastes as stabilizer agents for soils. In the current investigation, textiled-poly bags (TPB) have been recycled and fabricated to be economy and environmentally-friendly fibers. The impact of utilizing different proportions and lengths of these fibers on the mechanical features of clayey soil has been evaluated. The investigation depended on four different fiber-proportions (1, 2, 3, and 4%) of soil weight in two different lengths (1 and 2) cm. Geotechnical experimental test consequences demonstrated that the recycled fiber pieces minimize the optimum dry density and the corresponding optimum water content of the treated soil samples. In addition, there was a notable increment in the uniaxial compression test results of the treated soil samples. Moreover, the consequences of California Bearing Ratio tests showed that the utilization of recycled TPB fibers in clayey soil samples enhances the resistance and deformation performance of the soils specially when utilizing 4% of recycled TPB fibers for both lengths (1 and 2) cm. This recycled fiber improves the strength features and dynamic behaviors of clayey soils. Therefore, the recycled TPB fibers could be successfully utilized as reinforcement materials for the modification of clayey soils. [ABSTRACT FROM AUTHOR]

In this paper, a simplified chemo‐hydro‐mechanics (CHM) model, in which only solute concentration is considered in the aspect of chemistry, is proposed to reflect the viscoelastic deformation of clay soil. By using the proposed model, the responses of the excess pore‐fluid pressure, solute concentration, and displacement of the viscoelastic clay soil are derived through the Laplace transform method. Then, semi‐analytical solutions, in the time domain, are obtained via the inverse Laplace transform numerically. The influences of viscosity on excess pore‐fluid pressure, solute concentration, and displacement are investigated through an illustrative example. The results show that: (1) the clay soil in low viscosity can be simplified as an elastic model; (2) the higher viscosity not only accelerates the dissipation of excess pore‐fluid pressure, but also slows down the deformation of the clay soil; (3) the viscosity of clay soil poses little impact on the distribution of solute concentration. [ABSTRACT FROM AUTHOR]

The soil contaminated by oil product has geotechnical and environmental issues that rise from leakages in oil storage tanks, accidental spills, and supply and transition pipelines. For instance, a leakage has been recorded in the refinery station near the vicinity of Nineveh province where the soil's site is known with its high plasticity. The present study investigated comprehensively the engineering properties of soil contaminated with crude oil, diesel, kerosene, and gasoline at both dry and wet sides of compaction curve. Results show that the shape of the compaction curve changes to a double peak curve with a reduction in maximum dry density of 6% due to oils contamination. The soil plasticity decreases by approximately two-third upon contamination. Furthermore, the swelling percent increases by 1.9 to 2.5 times on dry side and by 3.8 to 4.3 times on wet side. The swelling pressure also increases by 1.2 times for soil contaminated with 5% diesel or 4% kerosene, while it decreases with crude oil. Strength results show that the cohesion (C) decreases by 45.2, 60.8, and 78.8% upon soil contaminated with 18% crude oil, 17% diesel, and 17% kerosene respectively; however, the corresponding angle of internal friction (ϕ) increases by several degrees. Likewise, a considerable reduction in the unconfined compressive strength is reported upon contamination. Moreover, the permeability decreases by 25% to 50% on dry side while it increases 2 times on wet side. [ABSTRACT FROM AUTHOR]

In other words, although soil mineralogy may well play a key role in the varying strength of clays with the water content, I c i SB u(FC) sb mobilised at the FC liquid-limit water content does not respond in any significant way to soil mineralogy; the same conclusion has been previously reported by O'Kelly I et al i . ([16]) employed a Geonor G-200 model 60°-60 g FC device to determine the apparent variations of I c i SB u(FC) sb with the water content about the I w i SB L-FC(BSI) sb (established using the 30°-80 g FC device) for the various fine-grained soils investigated. Keywords: Liquid limit; fall-cone; cone factor; undrained strength; fine-grained soil EN Liquid limit fall-cone cone factor undrained strength fine-grained soil 170 174 5 04/04/23 20230301 NES 230301 It is the authors' opinion that confusion could arise from the analyses and explanations of the experimental fall-cone (FC) results presented in the paper by Nagaraj I et al i . Figure 1(a): An x:y scatter plot showing the changes in undrained shear strength at the British Standard fall-cone liquid-limit water content against the British Standard fall-cone liquid-limit water content for six different fine-grained soils investigated by Nagaraj et al. (2018). [Extracted from the article]

In geotechnical projects involving soft soils, cement-mixed soils are an excellent way to improve the mechanical behaviour and engineering performance of soils. The water-to-cement ratio, cement content, and porosity are the most critical parameters impacting the strength of cement-mixed soils, but their effects are less well understood. The proportional influence of cement amount, porosity, and moisture content on cement-mixed soil strength is investigated in this research. The results showed that as the water-to-cement ratio increases, the influence of cementation and porosity on unconfined compressive strength decreases. The blended volume ratio is proposed as a new and adequate index for evaluating cement-mixed soil strength based on the experimental results. The blended volume ratio is the product of the void/cement volume ratio and the water/cement volume ratio. While the current index has not fully addressed the important effects of the water-to-cement ratio and porosity, the blended volume ratio allows describing the concurrent influences of porosity, cement amount, and water amount on the strength development. The experimental results showed that the cement-mixed soil strength is a function of the blended volume ratio. An empirical equation based on the blended volume ratio was then proposed for predicting the strength of cement-mixed soils. The validation of the proposed equation is verified by strength analysis for several different test data sets. A good agreement between measured and predicted results indicated that the proposed model is applicable to predict well the strength of cement-mixed soils. [ABSTRACT FROM AUTHOR]

Clay-mineral composition is one of the factors that determine the physical and engineering behaviours of finegrained soils; however, it is usually ignored in soil investigations, because the determination of clay-mineral composition necessitates using sophisticated instruments which are time-consuming and require skilled personnel. Many correlations exist for faster prediction of soil engineering properties from its index properties, but correlations for quicker determination of the amount of clay mineral in the soil are still unexplored. This study focuses on determining the amount of clay mineral present in a soil sample rapidly by correlating claymineral percentages with soil index and chemical properties, which aids in selecting proper construction guidelines before undertaking construction work. Clay-soil samples collected from 20 different locations in Tamil Nadu state in India were subjected to chemical tests, like cation exchange capacity (CEC), specific surface area (SSA) and total potassium (TP), to quantify clay minerals such as kaolinite, illite and montmorillonite. Correlations were developed for kaolinite, illite and montmorillonite percentages in terms of chemical (CEC, SSA and TP) and index properties. It was observed that the montmorillonite percentage has shown a stronger correlation with soil index properties than illite and kaolinite percentages, because of its physico-chemical behaviour. [ABSTRACT FROM AUTHOR]

To clarify the phenomenon of repeated segregated ice during the freeze-thaw cycle and improve the theory of soil freezing and thawing, a coupled hydro-thermal model was derived on the premise of previous theories, which described the soil deformation utilizing the Clapeyron equation of thermodynamic equilibrium in the phase change process. Then, the experiments being repeated to separate frost heaving and thawed moisture migration of saturated clayey soil were conducted. Results show that during the freezing period, the temperature change of each measurement point is consistent, and there exists a significant hysteresis with the distance from the cold source. The migration rate of unfrozen water to the freezing front driven by the temperature gradient is related to the freezing rate and has a constant dynamic trend with the frost heave. During the thawing period, there are obvious variations in temperature changes at each measurement point, and therefore the temperature change of the soil layer near the central heating layer is larger. The water supplement rate is comparatively slow, and there exists a trend from gentle to rapid growth. Under the fitted actual experimental boundary conditions, the system of nonlinear differential equations for hydrothermal coupling is solved by COMSOL Multiphysics software. The conclusions obtained in the study provide a reference to freeze-thaw practice. [ABSTRACT FROM AUTHOR]

This research aims to improve the engineering properties of expansive soil by using locally low-cost materials such as crushed glass wastes and lime. The studied expansive soil is considered unsuitable soil for civil engineering projects such as roads and buildings, as it was classified according to the AASHTO classification A-7-6. This soil was treated only with different ratios of crushed glass wastes (0%, 5%, 10%, 15%, and 20% by weight of dry soil), as well as the soil was treated only with different ratios of lime (0%, 2%, 4%, 6%, and 8% by weight of dry soil). Experiments of Atterberg limits, standard Procter, direct shear, free swell, swelling pressure, and both un-soaked and soaked California Bearing Ratio tests were carried out on the untreated and treated soil. The results showed that by increasing added percentage of crushed glass wastes and lime separately, the consistency properties (Atterberg limits), the shear strength parameters (direct shear test), free swell, swelling pressure, and both un-soaked and soaked California Bearing Ratio of the studied expansive soil were improved; except for compaction characteristics, by adding crushed glass wastes the M.D.D was increased and O.M.C was decreased while by adding lime, the M.D.D was decreased and O.M.C was increased. This helps to make use of low-cost local materials, clean the environment of glass wastes, and recycle these wastes so that they can be used on an environmental, economic, and engineering level. This aligns with Egypt's Vision 2030 sustainable development approach in both the environmental and economic dimensions. [ABSTRACT FROM AUTHOR]

In the last decade, biopolymers have been used as organic soil binders in ground improvement and earthen construction material modification. Although biopolymer-treated soils have substantially enhanced mechanical strength, the deformation characteristics under external loads and material durability (e.g. biodeterioration due to microbial activity) have not yet been fully understood, which limits the in situ practical application of the biopolymer-based soil treatment technology. This study investigated the efficiency of combined carrageenan and casein in strengthening a clayey soil with the biodeterioration consideration. Both mechanical tests (e.g. unconfined compressive strength and one-dimensional consolidation) and biological tests (e.g. high throughput sequencing and rating of mould growth) were conducted. Results indicated that the usage of the carrageenan–casein mixture induced a higher soil compressive strength compared with either carrageen or casein, due to the formation of a three-dimensional gel network. In addition, carrageenan–casein mixture and casein decreased the compressibility of the clayey soil, which might be attributed to the casein's peculiarity of self-associating into micelles, leading to minimal interactions with water molecules. Carrageenan, due to its affinity for water, increased the soil compressibility. Under the impact of microbial activity, the biopolymer-treated soils underwent deterioration in both surface appearance (i.e. coloured stains and patches caused by mould growth) and compressive strength. A linear relationship was proposed, in which a reduction in compressive strength by approximately 11% is expected while the rating of mould growth is increased by one in a five-rating system. The current research demonstrates that the soil reinforcement with combined carrageenan and casein is able to improve both soil strength and deformation behaviours. It is also suggested to take into account the biodeterioration considerations in the design and implementation of biopolymer-based soil reinforcement practices. [ABSTRACT FROM AUTHOR]

The current study investigates the deformation and strength of Light-Weighted Soil (LWS) comprised of silt, Expanded Polystyrene (EPS) beads, cement, and water. The EPS bead sizes employed in this study are 4, 5, and 6mm in diameter with densities of 0.011, 0.009, and 0.006g/cm3 and cement concentrations of 10% and 15%. The effects of different EPS bead sizes and cement proportions on the mechanical properties (strength and deformation) of LWS are evaluated by Unconfined Compression Strength (UCS) tests. The findings show that the EPS bead sizes significantly impact the strength and deformations of the LWS. The smaller the EPS bead size, the higher the observed strength, but, on the other hand, bigger EPS bead sizes have lower strength and higher ductility. It was also revealed that the strength of LSW is entirely dependent on the cement concentration. High cement content in the LWS has more strength and brittleness, but it is more prone to deformation. The cost can be decreased by increasing the EPS bead size, and thus the prescription of mixed soil can be enhanced. The use of EPS beads with a diameter of 4-6mm is recommended in the construction process, especially in backfill for retaining walls. Each EPS bead size provides advantages in different context, depending on engineering applications and field conditions. [ABSTRACT FROM AUTHOR]

The drying phenomenon in clays is a multiphysical process accompanied by alterations in the thermal, hydraulic, and mechanical states of the multiphase system. Reversible and irreversible characteristics of shrinkage deformation have been observed experimentally in clayey soils for different ranges of moisture contents. The kinematics of drying due to evaporation and drying-induced shrinkage can be studied by utilizing a coupled thermo-hydro-mechanical (THM) model. An accurate evaluation of drying-induced shrinkage is needed to investigate the thermal cracking and damage of geomaterials. In this study, we developed a thermoporoelastoplastic constitutive framework assuming a non-associative plastic flow rule that can accurately model the transversely isotropic behavior of stiff natural clays in unsaturated conditions. All material parameters used in the non-associative transversely isotropic constitutive model were calibrated based on experimental observations of Boom clay. Then, the capability of the model was assessed by analyzing the convective drying experiment on natural Boom clay. The comparison of the numerical and experimental results confirms the plausibility of the hypotheses made in this study. The results show that the first stage of evaporation ends rapidly and the falling rate period (second stage of evaporation) is the dominant evaporation mechanism due to the intrinsic hydraulic properties of Boom clay and the high evaporative demand of the environment. The developed model reasonably captures the anisotropic elastic and plastic deformations of the clayey soil during the transient drying process. Numerical results demonstrate that drying shrinkage induces a 30% reduction in porosity in which approximately 82% of the total volumetric deformation in drying-induced shrinkage is irrecoverable (i.e., plastic). Moreover, the results indicate that most of the plastic deformation occurs in the first couple of hours of the drying process, when the soil's unsaturated condition is in a funicular state (i.e., where capillary pressure is dominant). Finally, the last section of this paper is devoted to a sensitivity analysis of the THM behavior of Boom clay with respect to its elastic and plastic strength. The parametric study shows approximately 10% more reduction in the final surface shrinkage when the difference between the slopes of the drying-induced compression line and the swelling line (i.e., λ−κ) is doubled. [ABSTRACT FROM AUTHOR]

The moisture migration and high-volume changes due to swelling and shrinkage in the expansive soils have posed severe challenges at many project sites. Additionally, rapid industrialisation in last few decades has posed problems of huge amount of undisposed industrial wastes, which not only cause environment degradation but also occupy huge tracts of valuable land. The paper presents the results of an experimental investigation carried out to assess the effect of waste recycled product (WRP), an industrial waste from steel industries; on the engineering properties of expansive soil and to achieve dual objectives of improving the engineering performance of such soils combined with its gainful utilisation. Test results revealed that addition of WRP to expansive soil in appropriate proportion not only reduces its swelling and shrinkage behaviour but also there is a significant improvement in its strength and deformation characteristics. After adding 30% WRP (by dry weight of soil) in expansive soil, the percentage increase in subgrade modulus and unconfined compressive strength was 89.18% and 68.78%, respectively, and it is concluded that there is significant potential for its use in flexible pavement construction on expansive soil subgrade which in turn provides its safe and economical disposal. [ABSTRACT FROM AUTHOR]

Consolidation and creep are two types of time-dependent deformation of clay soil. However, the soil deformation presents probabilistic behaviours when the spatial variability is considered. The Monte–Carlo method is used to sample anisotropic random fields that are mapped into two-dimensional random finite element models (RFEM) to analyse the influences of spatial variability on the time-dependent deformation of clay soil. The anisotropic random fields of soil parameters are generated by a spectral representation method (SRM) to describe the spatial variability of clay soil. The consolidation and the creep problems are modelled by Biot's consolidation theory and the creep model proposed by Yin et al. (2010) respectively. The spatial variability of Young modulus and permeability coefficient in probabilistic consolidation analysis and the secondary consolidation coefficient in probabilistic creep analysis are emphasized by the RFEM simulation. The results show that the scale of fluctuation (SOF) in vertical direction and the coefficient of variation (COV) of Young modulus and permeability have significant influences on the probabilistic characteristics of consolidation behaviour. Besides, the bunched region of low permeability soil produces a blockage effect, which seriously affects the consolidation characteristics. It is found that the uncertainty of creep deformation will accumulate over time until it remains constant. The variability of creep deformation increases with the increase in the vertical SOF and COV of the secondary consolidation coefficient. The research also provides insightful clues for the time-varying reliability design related to the time-dependent deformation of clay soil. [ABSTRACT FROM AUTHOR]

In situ soils of deep overburden layer of dam foundation are widely distributed in Southwest China, which are mixtures of gravel and silty clay in varying proportions and have cementation feature between soil particles. Based on a series of triaxial compression tests carried out on artificially cemented mixed soils (CMS) and remolded mixed soils (RMS) at confining pressures of 50, 100, 200 and 400 kPa with fine contents (silty clay) of 13%-70% in mass, a binary-medium constitutive model for artificially cemented mixed soils is proposed within framework of breakage mechanics theory for geological materials and homogenization theory. This model was formulated by regarding the soils as a binary medium consisting of bonded blocks (idealized as bonded elements) and weakened bands (idealized as frictional elements), whose deformation properties are described by the modified Duncan-Chang model and the Lade-Duncan elastoplastic model, respectively. The non-uniform distribution of stress and strain within a representative volume element can be given by introducing the structural parameters of breakage ratio and local stress coefficient. Comparisons of computed results with test results demonstrate that the binary-medium constitutive model can reflect mechanical properties of artificially cemented mixed soils well. [ABSTRACT FROM AUTHOR]

This paper examines the accuracy of a new elastic–thermoviscoplastic (E-TVP) constitutive model developed based on critical state soil mechanics. The model can be used for simulating the temperature-dependent and strain-rate-dependent behavior of clay soils. The study compares the E-TVP behavior of a single soil element with previously published thermo-mechanical experimental results performed on saturated clay specimens at different temperatures. Suggestions regarding unloading and reloading at constant temperatures as well as thermal consolidation under constant loads are presented. A modification for unloading–reloading adds a new criterion to the volumetric thermoviscoplastic strain rate formulation. A physics-based term is added to the current specific volume of the soil to include the viscous effect induced by temperature change. These modifications improve the convergence of laboratory data and simulated model responses. Comparisons of results from an earlier E-TVP model and the newly improved model provide evidence of improved predictive capabilities. [ABSTRACT FROM AUTHOR]

Grouser height and soil moisture content have a significant effect on the tractive performance of tracked vehicles. Paddy soil has the mechanical properties of both clay soil and sandy soil and can have a wide range of water content values, and it has a considerable influence on the tractive performance of tracked agricultural machinery. To study the influence of grouser height on the tractive performance of a single-track shoe under different soil moisture contents, a three-dimensional shearing model of the single-track shoe and the contact soil was established based on the ground vehicle mechanics theory, and an experimental platform with a soil bin, sensors, and a control system was established. Six preset levels of moisture contents (7%, 12%, 17%, 22%, 27%, and 32%) of paddy soil were prepared for the research experiment. The mechanical properties of the soil with different moisture contents were obtained through the use of a direct shear test, penetration test, and compaction test. The obtained physical parameters of the soil have special characteristics that are different from typical soil. Combined with the three-dimensional model and the obtained soil parameters, the parameters of the tractive performance, such as thrust, running resistance, and traction with different moisture contents were analyzed and calculated. The test results revealed that the thrust at different grouser heights shows a regular waveform growth trend with an increase in soil moisture content. The minimum value and the maximum value of thrust were obtained at moisture contents of 7% and 12%, respectively. The curve of different grouser heights of the running resistance shows similar changes with different moisture contents. The two peak points and inflection points of the fluctuation curve are for moisture contents of 17% and 27%. The change curve of the traction is highly similar to the curve of thrust. The maximum value of the traction was found at a moisture content of 12%, and the minimum value at 22% or 27%. Under different moisture conditions, tracked vehicles with higher grousers have better tractive performances. [ABSTRACT FROM AUTHOR]

This study quantified the immediate impact of soil deformation caused by agricultural vehicle traffic on the anisotropy of the topsoil pore system and gas transport properties (air permeability, gas diffusivity). A field experiment was conducted with five repeated passes of a two-axle self-propelled agricultural vehicle (wheel load 8 Mg, tyre size: 1050/50 R32, tyre inflation pressure: 100 kPa) on an arable clay soil (crop at the time of the experiment: grass ley) in north-western Switzerland. Undisturbed cylindrical soil cores were collected in non-wheeled areas, at the edge of the wheel rut (i.e., at 0.5 m lateral distance from the centre of the wheel track), and at the centre line of the wheel track. The soil cores (0.1 m diameter, 0.06 m in height) were taken in two directions (vertical and horizontal) in the topsoil (0.1 m depth). Air-filled porosity (ε a), air permeability (k a) and relative gas diffusivity (D p / D 0) were measured at three matric potentials (corresponding to p F 1.5, 2.0, and 2.5, respectively). The vehicle-induced deformation resulted in significantly reduced ε a , k a , D p / D 0 in the topsoil. Air permeability was highly anisotropic in non-wheeled soil, with higher k a in vertical direction. Compaction mainly affected macropores and hence k a at the wet end (p F 1.5), decreased the vertical k a more than the horizontal k a , and consequently, k a became less anisotropic due to compaction. This effect was stronger under the edge of the wheel rut than in the centre of the wheel rut. The anisotropy of D p / D 0 was little affected by the vehicle-induced soil deformation. Our results show that soil deformation due to vehicle traffic not only decreases the gas transport capacity of soil but also changes the anisotropy of air permeability, with consequences on soil aeration and soil-atmosphere gas exchange. • Impacts of wheeling are different under the centre and under the edge of the wheel rut. • Wheeling decreased the gas transport properties and changed the anisotropy. • Air permeability was more affected than gas diffusivity. [ABSTRACT FROM AUTHOR]

To prevent the cracking of silty clay under cyclic wet-dry cycling (W-D), which leads to the increase of deformation and strength attenuation of silty clay, microencapsulated phase change material (mPCM) was used to improve it. The deformation and strength characteristics of silt with different dosages (1 %, 2 % and 4 %) of mPCM and their changing patterns were analyzed and studied by indoor compaction test, crack observation test, consolidation test and straight shear test, and compared with silt without modifier. The results showed that with the increase of mPCM dosage, the optimum water content of silt and the maximum dry density decreased. A 2 % dosage of mPCM inhibited the development of silty clay cracks, reduced crack width and deformation, and increased the compression modulus of the soil samples by nearly 2.3 times. Under dry and wet cycling conditions, the cohesion decay of silty clay is greater than the angle of internal friction. The addition of 2 % mPCM significantly increased the shear strength of silty clay, cohesion by nearly 2.1 times, and internal friction angle by 1.4 times. The mPCM inhibits crack development mainly by regulating the internal temperature field of soil samples, thus improving soil strength. This study provides a reference for inhibiting soil cracking from a new temperature perspective. • A new method for controlling the temperature gradient of silty clay to inhibit soil cracking using microencapsulated phase change materials is proposed. • With the addition of mPCM, the silty clay's optimum water content increased, and the maximum dry density decreased. • Incorporation of mPCM reduces the attenuation of shear strength of silty clay under dry and wet cyclic action. • This method can significantly improve silty clay's cracking resistance and reduce the soil's deformation characteristics. [ABSTRACT FROM AUTHOR]

In this work, the mechanics of cone penetration during CPTu tests in Osaka clay, a natural structured silty clay, was investigated with the Particle Finite Element Method (PFEM). To describe the behavior of the soil, the FD_MILAN model, recently proposed by the Authors, was adopted. The model, based on the multiplicative decomposition of the deformation gradient, incorporates a scalar internal variable, the bond strength P t , to quantify the effects of structure. The macroscopic description of mechanical destructuration effects is provided by the hardening law of P t , according to which the bond strength decreases monotonically with accumulated plastic deformations. The brittle behavior resulting from the softening process associated to destructuration make the soil quite susceptible to the spontaneous development of strain localization in the form of shear bands. In order to deal with strain localization phenomena, the model is equipped with a non-local version of the hardening laws, incorporating a material constant – the characteristic length ℓ c – which provides the material with an internal length scale. The objective of this work was to get some insight on the effects of the characteristic length and of the initial degree of structure on: the kinematics of the soil deformation around the advancing cone tip; the evolution of soil structure with accumulated plastic deformations; the excess pore pressure field generated in the soil as a result of the hydro-mechanical coupling between the solid skeleton and the pore water, and the net cone resistance measured at the base of the cone. The results of the PFEM simulations show that the deformations around the piezocone are strongly affected by the characteristic length. For heavily structured soils, when ℓ c is relatively small with respect to cone radius, the accumulated plastic deviatoric deformation field is characterized by clearly visible shear bands while, as ℓ c increases, the detection of localized deformation regions becomes more difficult, if not impossible. This depends on the fact that, for large values of ℓ c , the shear band width may be of comparable size to the cone radius. In all cases, the soil around the advancing piezocone is subjected to a very strong destructuration process, which leads to the complete loss of bond strength in a large region around the cone tip and shaft. As a consequence, the use of conventional N c values from the literature in the interpretation of the CPTu test performed in heavily structured soils could provide undrained strength values closer to the ultimate undrained shear strength. At the same time, the use of empirical correlation to estimate the yield stress in oedometric conditions would lead to a significant underestimation of the overconsolidation ratio. [ABSTRACT FROM AUTHOR]

In this paper, an attempt has been made to investigate the impacts of leaching on the geotechnical and microstructural properties of clayey gypseous soils at various percentages of gypsum; 20 %, 40 %, and 60 %, and their respective densities. In this respect, the work delves into the interaction of the properties based on the following experiments: oedometer permeability leaching and modified permeability leaching tests for investigating the effects of gypsum content, density, and leachate on significant soil properties such as compressibility, permeability, and Total dissolved solids (TDS). Scanning electron microscopy (SEM) and Energy dispersive spectroscopy (EDS) used for microstructural analysis reveal how the soil fabric and dissolution patterns change during leaching. The conclusions derived from the results of the study state that with an increase in the content of gypsum in soil, it increases the porosity and permeability of the soil and at the same time decreases the plasticity. The soils which were denser showed lesser leaching strain due to reduced permeability. It can be ascertained that the modified leaching test is a more realistic and accurate method in comparison to the oedometer test. Results from microstructural observations hence bring out important changes in the soil fabric after leaching: increases in voids and cavities responsible for the change of soil stability and engineering properties. This research allows a good contribution to understanding and the management of gypseous soil behavior in geotechnical engineering projects and provides new lines of future investigation for the long-term performance and stabilization technique of effectiveness. [ABSTRACT FROM AUTHOR]

Liquefaction of sandy soils is a big threat to the stability and the safety of an earth embankment laid on saturated soils. A large number of liquefaction-induced damages on embankment due to different types of earthquakes have been reported worldwide. In this research, the dynamic behaviors of earth embankment and the reinforcement effects of grouting as remediation method, subjected to moderate earthquake EQ1 and strong earthquake EQ2, were numerically investigated. The seismic behaviors of ground composed of cohesionless sandy soil and cohesive clayey soil were uniformly described by the cyclic mobility (CM) model, which is capable of describing accurately the mechanical property of the soil due to monotonic and cyclic loadings by accounting for stress-induced anisotropy, over-consolidation, and soil structure. It is known from the numerical investigation that the embankment would experience destructive deformation, and that the collapse mode was closely related to the properties of input seismic motion because high intensities and long durations of an earthquake motion could lead to significant plastic deformation and prolonged soil liquefaction. Under the strong seismic loading of EQ2, a circular collapse surface, combined with huge settlement and lateral spread, occurred inside the liquefication zone and extended towards the embankment crest. In contrast, in moderate earthquake EQ1, upheaval was observed at each toe of the embankment, and instability occurred only in the liquefied ground. An anti-liquefaction remediation via grouting was determined to significantly reduce liquefaction-induced deformation (settlement, lateral spreading, and local uplift) and restrain the deep-seated circular sliding failure, even though the top sandy soil liquefied in both earthquakes. When the structure was subjected to EQ2 motion, local failure occurred on the embankment slope reinforced with grouting, and thus, an additional appropriate countermeasure should be implemented to further strengthen the slope. For both input motions, the surface deformation of the considered embankment decreased gradually as the thickness of reinforcement was increased, although the reinforcement effect was no longer significant once the thickness exceeded 6 m. [ABSTRACT FROM AUTHOR]

Using stationary electrochemical, polarization resistance, cathodic charging, transient electrochemical impedance spectroscopy, and theoretical and molecular mechanics studies, epoxy polymer-coated carbon steel specimens' ability to protect metals from corrosion in various soil extracts was examined. According to the polarization resistance tests results, the polymer coating remained stable for 60 days in all three soil extracts, with a 90% efficiency for the steel coated in Soil Extract A, indicating that the sandy soil is less aggressive than the other two. The aggressiveness of clay soil was confirmed by the fact that a polymer-coated steel rod in the clay soil extract experienced a corrosion current density of 97 µA/cm2. In contrast, the same rod in sandy soil had a current density of 58 µA/cm2. The coating's good adsorption contact with the metal surface was further guaranteed by molecular dynamics simulations, which provided atomic-level evidence of the epoxy molecule's adsorption behavior (geometry) and adsorption energy on the carbon steel surface. [ABSTRACT FROM AUTHOR]

Civil engineers face significant challenges in the safe design and construction of durable road infrastructure in the presence of expansive soils. These problematic soils exacerbate undesirable serviceability concerns induced by pavement distress. Soil stabilisation has been recognised as a sustainable approach to alleviate the problematic nature of expansive subgrades. Road pavements constructed on top of expansive subgrade soils are generally under unsaturated conditions, where the moisture variations can significantly impact the pavement response. However, current pavement design and modelling frameworks overlook unsaturated soil behaviour by adopting simplified approaches. This study examines the hydraulic behaviour of expansive clayey soils stabilised with non-traditional and traditional chemical based additive. Tests were conducted to determine the state variation and stabilisation influence on the soil water characteristic curve using the dewpoint potentiometer for an expansive subgrade commonly found in Melbourne geology. Results show that the stabilisation has strong influence on soil hydraulic characteristics at various initial state conditions tested. Experimental data have been applied to illustrate the significance of incorporating realistic hydraulic response using a simulated practical application in road pavements. The research highlights the significance of incorporating accurate hydraulic characteristics for simulating and assessing the response of pavement constructed with stabilised unsaturated subgrade soils. [ABSTRACT FROM AUTHOR]

This paper presents a combined experimental‐modeling effort to interpret the coupled thermo‐hydro‐mechanical behaviors of the freezing soil, where an unconfined, fully saturated clay is frozen due to a temperature gradient. By leveraging the rich experimental data from the microCT images and the measurements taken during the freezing process, we examine not only how the growth of ice induces volumetric changes of the soil in the fully saturated specimen but also how the presence and propagation of the freezing fringe front may evolve the anisotropy of the effective media of the soil–ice mixture that cannot be otherwise captured phenomenologically in the isotropic saturation‐dependent critical state models for plasticity. The resultant model is not only helpful for providing a qualitative description of how freezing affects the volumetric responses of the clayey material, but also provide a mean to generate more precise predictions for the heaving due to the freezing of the ground. [ABSTRACT FROM AUTHOR]

Landslides are geologic hazards that threaten human life, property, and infrastructure. Proper mitigation requires knowledge of where landslides occurred in the past. Until recently, no landslide inventory maps had been published for any area of Alaska. Here, we present a short overview of landslide mapping within the Fairbanks North Star Borough (FNSB), Alaska, and a focused investigation of the Tanana 440 (T440) landslide. We mapped 1,679 landslides and field-verified 51 landslides within the FNSB. These landslides vary in age, movement type, and material. We present the results of in-depth mapping; subsurface exploration; soil engineering properties, including results of direct shear testing; and slope stability analysis of the T440 landslide, which we determined is a flow slide in loess that occurred during the late Pleistocene to mid-Holocene. We modeled seven slope stability scenarios for the T440 landslide by varying water table position and seismic load. Our modeling results suggest that thawing permafrost and/or seismic loading were likely possible triggers for the T440 landslide. To our knowledge, we present the first comprehensive direct shear testing of non-plastic silt with a variation in moisture content and the first comparison of direct shear and field vane shear measurements of silt. The average cohesion and internal friction angle of the wetted remolded silt were 3.0 kPa and 23.1°, respectively. These values did not significantly change with increasing moisture content. The direct shear and vane shear strengths of silt had low correlation (R² = 0.20), unlike the strong correlation that is typical of clay soils. [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]

Australian design practice for granular pavements with lime-modified subgrades is very conservative and does not consider the initial and long-term strength improvement. It recommends that the assigned California bearing ratio (CBR) of a modified subgrade soil should not exceed 15% for most roads. Two types of clay soils with plasticity indices of 22% and 42.5% were treated herein with their minimum lime demand (MLD) and tested to evaluate the modification influence on their properties. These properties include pH, compaction, compressive strength, bearing capacity, resilient modulus, and permanent deformation. Three different mellowing periods, 24, 48, and 72 h, between lime treatment and compaction, were used in this study to identify their optimum mellowing periods. Analysis of testing results for long-term compressive strength and CBR showed that MLD improves both soils' compressive strength and bearing capacity. Using the actual CBR values of lime-treated soils in designing the cover over subgrade results in a 30% reduction in pavement thickness. Lime modification of these soils also improves their resilient moduli and permanent deformation. The best results are achieved with mellowing periods of 24 h for Soil A and 72 h for Soil B. These optimum mellowing periods reduced permanent deformation of Soil A to less than 0.15% and 0.11% for Soil A. Considering the study findings, it is believed that thinner pavements can be designed and built on modified subgrades with MLD, which will help road agencies save funds. [ABSTRACT FROM AUTHOR]

2 of the original paper" and that "For soils and rocks under undrained condition, HT ht has been proven theoretically to be equal to 0.5 when the Skempton ([22]) HT ht parameter is equal to 1 at fully saturated conditions." For instance, for very stiff clays at high confining pressures, the theoretical HT ht value may barely exceed 0.9 even at fully saturated conditions. The Skempton HT ht parameter depends on both the degree of saturation and the stiffness of the soil skeleton. 1, HT ht is more affected by changes in degree of saturation and confining pressure at small strain conditions compared to large strain conditions (e.g., [10]). [Extracted from the article]

Clay soils, usually in an unsaturated state, are widely used as barrier materials in solid waste landfills. When the saturation of clay soils is high, the gas phase will be in the form of entrapped bubbles. The entrapped bubbles can directly affect the soil hydraulic behavior, which further affects solute transport in clay liner. Therefore, based on the stress balance, fluid mass conservation, and solute mass conservation equations, and combined with the relationship between pore water pressure and air pressure in unsaturated state, a coupled hydro-mechanical-chemical model has been put forward to study the influence of entrapped bubbles on solute transport process. Using the proposed model, a series of numerical calculations are carried out through the finite element simulation software COMSOL Multiphysics. The numerical results show that the increase of entrapped bubble content can enlarge soil deformation and slow down the rates of excess pore fluid pressure dissipation and solute transport. In particular, when the degree of saturation in air phase increases from 0 to 0.2, the difference of influence depth at the transport time 10 years reaches 28 cm, and the breakthrough time of solute is prolonged by 17.8 years. [ABSTRACT FROM AUTHOR]

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.)

The application of biological processes to improve the behavior of soils remains a concern among the scientific, industrial, and public sectors. The amount of research in this field has increased in the last two decades. However, the complexities associated with this process for the types of soil and their heterogeneous behavior, longevity (i.e., durability), optimization of solutions and treatment methods, amount of calcite precipitation and uniformity in its distribution, upscaling in the field, and finding their effective measures require a comprehensive interdisciplinary research approach that combines geotechnical engineering, geochemistry, and microbiology. Therefore, this paper aims to encapsulate the research work from the last two decades by highlighting an overview of the mechanisms (i.e., biostimulation- and bioaugmentation-induced calcite precipitation) associated with the implications of biogeotechnology to improve the different soil types. The most commonly used biological processes [i.e., ureolysis or urea hydrolysis, denitrification, and sulfate (SO42–) or iron (Fe) reduction] will be compared for their suitability, limitations, and associated bacteria and strains that are used for the biotreatment of soils. In addition, various limiting factors that control the successful application of microbial-induced carbonate precipitation (MICP) to improve the properties of soils are highlighted. The fundamental differences between the biotreatment processes from the laboratory to field scale (e.g., injection method, surface percolation method, and premixing method) will be explained categorically. This paper will discuss the current status, challenges, and future opportunities in biogeotechnology. The application of biogeotechnology to improve the behavior of clayey soil requires more attention compared with sandy or silty soils. The major limitations, biological concerns, consequences, and their possible controlling measures will be discussed to understand the complexity when adopting biological processes in geotechnical projects and practices. Finally, the paper lists out the potential areas that should be focused on for the effective, economical, sustainable, and durable application of biogeotechnology under various construction conditions. [ABSTRACT FROM AUTHOR]

The jack-up platform is prone to punch-through accidents during the installation and preloading. How to effectively predict the bearing capacity of spudcan is a major concern in the industry. This paper reports a new method for predicting spudcan penetration curves on stiff-over-soft clay based on numerical results. A three-dimensional nonlinear numerical model of "spudcan-seabed" is established using the CEL method of ABAQUS software with the remolding softening characteristic of saturated clay considered. A comprehensive parametric study is carried out to analyze the soil deformation beneath the spudcan and the spudcan bearing characteristics at both peak and post-peak of the penetration curve, varying the strength ratio between soft and stiff soil layers, the thickness of the stiff soil relative to the spudcan diameter, and the non-homogeneity of soft soil strength. Based on these numerical solutions, the formulas for calculating the bearing capacity and penetration depth of spudcan are established, and then the detailed procedure is given for constructing the penetration curve, at which the peak bearing capacity accounts for the vertical movement of soil under the spudcan. Finally, the comparison of the calculation results with centrifuge tests demonstrates the effectiveness of the new method in predicting the spudcan bearing capacity-penetration curve. • A new calculation method for bearing capacity of spudcan. • The movement variation of soil beneath a spudcan at both peak and post-peak of penetration curve. • Evaluation method of soil plug height. [ABSTRACT FROM AUTHOR]

• Clay content and subfreezing temperature coupling affect soil FT deformation. • The clay aggregate evolution during FT accounts for the complex deformation. • Full-range evolution of soil structure is characterized via NMR and X-CT. • Quantitatively analyze contribution of micro/meso structure change to deformation. Climate change brought about significant freeze–thaw (FT) deformation of clayey soils distributed in cold regions, which resulted from soil structure evolution including pore size distribution change and crack development. However, the formation of clay aggregate that dominates the soil deformation behavior during FT remains unclear. This study investigated the effects of clay contents (5 %, 10 %, 15 %, and 20 %) and subfreezing temperatures (−5 °C, −10 °C, and −15 °C) on the soil FT deformation properties by isotropic isothermal FT tests. Meanwhile, the soil structure evolution was characterized via Nuclear Magnetic Resonance and X-ray Computed Tomography. The results indicated that the frost heave ratio (η) and thaw settlement coefficient (δ) non-linearly varied with clay content and subfreezing temperature. Specifically, the minimum η and δ were observed in the specimen with 10 % clay content, and the maximum η and δ were identified at −10 °C. This phenomenon can be attributed to the clay aggregate forming bimodal or unimodal pore size distribution (PSD) with different initial clay contents. The freezing characteristics of inter- and intra-aggregate pore water were determined by the solid-water interaction. Moreover, the FT action altered the structure of clayey soil by the change in PSD and the generation of cracks. The contribution of pore size change and crack development to the total volume change before and after FT was quantitatively analyzed. It demonstrated that pore size change was more important for the total volume change in specimens with lower clay content and higher subfreezing temperature, whereas crack development mainly contributed to the total volume change in the rest of the specimens. This study provides a deep insight into the deformation characteristics of clayey soils under different climate conditions in cold regions. [ABSTRACT FROM AUTHOR]

Purpose: Soil cracking is a common natural phenomenon. The existence of soil cracks has significant effects on the engineering properties of clayey soil, and can cause significant problems in geotechnical, geological, and environmental aspects. Understanding of the potential mechanisms of soil cracking is essential in assessments of potential damages to earthen infrastructures. Materials and method: We review the past research efforts devoted to the experimental investigations and applications of fracture mechanics in soil cracking, attempting to provide a better understanding of the formation mechanism of desiccation cracking with a perspective of fracture mechanics. Results and discussion: This review analyzes the influence of soil cracking on soil engineering properties and the significance of soil cracking phenomena. Past and current formulations of soil fracture criteria and their experimental investigation are discussed. This review reveals the factors that affect the mechanisms of soil fracture can be divided into two groups, namely soil intrinsic properties and test-related factors. The applications of fracture mechanics in soil cracking are also discussed with particular focus on soil fracture models that are separately based on linear elastic fracture mechanics (LEFM), elastic plastic fracture mechanics (EPFM), and numerical simulations of soil cracking based on fracture mechanics. Some challenges and prospects of the applications of fracture mechanics in soil cracking are presented. Conclusions: Fracture mechanics is a significant method to explain soil crack initiation and propagation. It is expected that researchers can gain better understanding of the range of fracture mechanics applications in soil cracking, and seek improvements and extensions of existing models through this review. [ABSTRACT FROM AUTHOR]

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.)

Building on expansive soil is risky due to its high compressibility, low shear strength, and differential settlement. This study evaluates the potential of the use of sodium hydroxide (NaOH) as an additive to improve the stability of clay. For this research, the compaction properties namely Dry Density, Optimum Moisture Content, Atterberg Limits, and Unconfined Compressive Strength were performed on soil samples prepared with different percentages of NaOH (0%, 5%, 10%, 15%, and 20%). In this work, the clay sample was obtained from a highway project site near the Haspolat village in the eastern suburb of North Nicosia, Cyprus. No works of such have been done in the area. The results indicated that NaOH can be added to improve the engineering properties of the soil. Moreover, this paper presents a comparative study between an empirical equation (Quadratic model (QM)), Multilayer Feed-Forward Neural Network (MFFNN), Cascade Feed-forward Neural Network (CFNN), Radial Basis Neural Network (RBNN), and Elman neural network (ENN)) and multiple linear regression (MLR) for modeling the stress–strain behavior of CS15 (contains 85% of soil and 15% of NaOH). The coefficient of determination, root mean squared error, mean absolute error, Nash–Sutcliffe efficiency, and Willmott's index of the agreement were used to select the best predictive model. The results indicate that all the developed models are expedient in predicting the stress–strain behavior of treated soil. Furthermore, the findings demonstrated that the QM model performed well and presented high accuracy in modeling the stress–strain behavior. [ABSTRACT FROM AUTHOR]