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Calcareous sand has been widely used as a construction material for offshore projects; however, the problem of foundation settlement caused by particle crushing cannot be ignored. Although many methods for reinforcing calcareous sands have been proposed, they are difficult to apply on-site. In this study, a permeable polyurethane polymer adhesive (PPA) was used to reinforce calcareous sands, and its mechanical properties after reinforcement were investigated through compression creep, direct shear, and triaxial shear tests. The reinforcement mechanism was analyzed using optical microscopy, CT tomography, and mercury intrusion porosimetry. The experimental results indicate that there is a critical time during the compression creep process. Once the critical time is surpassed, creep accelerates again, causing failure of the traditional Burgers and Murayama models. The direct shear strength of the fiber- and geogrid-reinforced calcareous sand reinforced by PPA was approximately nine times greater than that without PPA. The influence of normal stress was not significant when the moisture content was less than 10%, but when the moisture content was more than 10%, the shear strength increased with an increase in vertical normal stress. Strain-softening features can be observed in triaxial shear tests under conditions of low confining pressure, and the relationship between the deviatoric stress and strain can be described using the Duncan–Chang model before softening occurs. The moisture content also has a significant influence on the peak strength and cohesive force but has little influence on the internal friction angle and Poisson's ratio. This influence is caused by the different PPA structures among the particles. The higher the moisture content, the greater the number of pores left after grouting PPA. [ABSTRACT FROM AUTHOR]

AbstractThe granular and natural characteristics of soil introduce size effects to its deformation and strength properties. Therefore, investigating the phenomenon of strain localisation in soil requires a multi-scale characterisation. This study examined the intrinsic scale patterns in samples with different sizes of reinforcing particles through triaxial compression tests. Additionally, the formation mechanism of microscopic shear bands was investigated using numerical simulation methods. Drawing from the soil cell model theory, the average strain energy release coefficient was introduced to validate the transformation of the overall strain energy of the specimen after reaching the peak stress. This reflects the progressive initiation and competitive process of multiple bands. The results indicate that samples with different sizes and types of reinforcing particles exhibit various failure patterns, including single-type, ‘x’-shaped, ‘v’-shaped, parallel and others. The soil exhibits size effects, with the ratio of intrinsic scale to particle size decreasing as the size of reinforcing particles increases. Prior to the stress peak, non-elastic dissipation energy begins to increase, indicating the initiation of plastic deformation in the soil. Localised strain zones are activated, and after the peak, there is a sharp increase in stress within the shear bands, accompanied by rebound outside the band. [ABSTRACT FROM AUTHOR]

The one-dimensional consolidation analysis of clays considering creep compression is a classical issue in soil mechanics and geotechnical design. The major debate lies in how to predict the consolidation settlement for a thick layer in the field using parameters obtained from a thin specimen from the laboratory. Different hypotheses have been advocated, based on which various methods and constitutive models have been developed. However, there are still some questions unaddressed and concepts inconsistently used, which may mislead engineers in the selection of methods/models and may result in settlements underestimated on a risk design side. In this paper, a state-of-the-art review and a thorough comparison study are performed on the existing methods and models for the consolidation analysis of clays exhibiting creep, from theoretical derivations to numerical simulations in comparison with soil test data. An in-depth discussion is carried out on several key issues related to the thickness effects on the time-dependent compression behaviour of clays. The arguments of Hypothesis A and Hypothesis B are revisited based on the current development of constitutive theories. Three existing elastic visco-plastic (EVP) models that consider the creep compression implicitly during the whole consolidation process can perform well in predicting the settlement of clay layers with different thicknesses, and are in line with Hypothesis B. It is concluded that using existing EVP models based on porous-media continuum mechanics is a rigorous scientific method (also called "rigorous" Hypothesis B method), which is superior to the old Hypothesis A method which has logic errors and may result in unsafe underestimation of settlements. [ABSTRACT FROM AUTHOR]

In our recent paper, we reported the development and application of the aerosol injection technique to accelerate the consolidation in soft soils. Aerosol injection technique is a process that involves injecting air under high pressure into soft soil to create a network of fractures, which gives rise to enhanced permeability. In this paper, we present an experimental study on the permeability of soft soil specimens with pre-made fractures in a triaxial device. Some emphasis is given to the variation of permeability with time. Some major influence factors are considered, e.g. the fracture roughness, confining pressure, pre-consolidation pressure, soil structure and mineral composition. The decrease in permeability with time is mainly due to the self-healing mechanism in soft soils, which is dictated by the soil deformation and migration of fines driven by the confining pressure and hydraulic gradient. [ABSTRACT FROM AUTHOR]

Existing numerical methods for modeling slurry infiltration often employ a fluid continuity equation commonly used in groundwater flow analysis. However, it is essential to account for the changes in fluid density and viscosity due to shifts in slurry concentration. In view of this, a multi-field numerical model is developed to simulate the slurry infiltration in saturated soil considering the coupling relationship between particle transportation, fluid seepage, and soil deformation. The governing equations of slurry infiltration are derived based on the mass conservation law. The permeability coefficient is modified through spatiotemporal variation of slurry viscosity, which is governed by concentration modifications. The calculated results are validated using the existing test data, which rectifies the issue of non-conservation of mass in the existing model based on the continuity condition of the liquid phase. Finally, the method is applied to a model of a slurry trench to simulate the process of slurry infiltration, including the spatiotemporal variation of deposition, fluid pressure, and concentration. The time of mud cake formation is determined based on the pressure–time distribution. It is found that the time of mud cake formation in the slurry trench can be shortened by increasing the slurry concentration. [ABSTRACT FROM AUTHOR]

The soil–water characteristic curve (SWCC) is the most fundamental relationship in unsaturated soil mechanics, relating the amount of water in the soil to the corresponding matric suction. From experimental evidence, it is known that SWCC exhibits hysteresis (i.e., wetting/drying path dependence). Various factors have been proposed as contributors to SWCC hysteresis, including air entrapment, contact angle hysteresis, ink-bottle effect, and change of soil fabric due to swelling and shrinkage; however, the significance of their contribution is debated. From our pore-scale numerical simulations, using the multiphase lattice Boltzmann method, we see that, even when controlling for all these factors, SWCC hysteresis still occurs, indicating that there is some underlying source that is not accounted for in these factors. We find this underlying source by comparing the liquid/gas phase distributions for simulated wetting and drying experiments of 2D and 3D granular packings. We see that during wetting (i.e., pore filling) many liquid bridges expand simultaneously and join together to fill the pores from the smallest to the largest, allowing menisci with larger radii of curvature (lower matric suction). Whereas, during drying (i.e., pore emptying), only the limited existing gas clusters can expand, which become constrained by the size of the pore openings surrounding them and result in menisci with smaller radii of curvature (higher matric suction). [ABSTRACT FROM AUTHOR]

Soil compaction is a serious threat to soil functions and ecosystem services. Persistent soil deformation takes place when mechanical stress exceeds soil strength. Risk assessment models typically assume soil to be elastic to a precompression stress level and plastic above this threshold. Currently used procedures for estimating soil precompression stress imply applied stress in a logarithmic form that has been criticized. We performed uniaxial, confined compression tests on 117 soil samples with a well‐defined stress history. Strain and stress were recorded at 200 levels of stress in the range of 0–1 MPa. Soil compressibility was calculated as incremental strain per incremental stress, using stress in arithmetic scale. For a given sample, a local minimum in compressibility appeared close to the preload applied to the sample prior to the compression test. This yield stress is suggested as an expression of soil precompression stress. Not all samples displayed a yield stress. Primarily soil exposed to a high preload did not exhibit a clear stress level with change in compressibility. This indicates that a physically based stress level pointing out a transition to plastic conditions will not exist for all soils. Our observation calls for new concepts in risk assessment. Tests with interpolation between a limited number of data points indicate that the yield stress—if existing—may be detected from classical compression data. [ABSTRACT FROM AUTHOR]

In contrast to cemented soils in terrestrial natural environments, cemented soils in littoral and marine geotechnical engineering face numerous difficulties. In coastal and marine geotechnical engineering, cemented soils are frequently degraded by ion erosion, tidal scouring, and temperature variations. Long-term marine environments present numerous challenges for cemented soil foundation projects. In marine geotechnical engineering, addressing and enhancing these degradation issues has become a crucial topic. To address this engineering problem, Nano-SiO2 is added to cement-stabilized soils to enhance their engineering performance. To investigate the mechanical effects and erosion mechanisms of Nano-SiO2 cemented soil subjected to chloride ion erosion and tidal alternation scouring, laboratory experiments, including immersion erosion tests with sodium chloride solution and dry-wet cycle tests, were designed. On specimens subjected to dry-wet cycles after chloride ion erosion at varying concentrations, unconfined compressive strength tests (UCS), X-ray diffraction (XRD) experiments, and scanning electron microscopy (SEM) were performed. The objective was to investigate the impact of chloride ions and Nano-SiO2 on the microstructure and strength of cemented soil. Adding 2.5% Nano-SiO2 can promote cement hydration reactions while preventing the entry of chloride ions into the cemented soil, thereby increasing the density and compressive strength of the cement. [ABSTRACT FROM AUTHOR]

The potential for pile tip damage and extrusion buckling has become an increasing concern for the offshore wind industry following the trend toward the use of large-diameter thin-walled pile foundations, either as monopiles or as part of a jacket structure. Extrusion buckling may be triggered by an initial pile tip fabrication imperfection or pile damage during transport and handling. It may also be triggered during driving through strong heterogeneous sediments. Numerical analysis of the problem requires advanced and computationally expensive techniques because of the three-dimensional, dynamic and large-deformation nature of the pile and soil deformations. The problem is addressed here by combining coupled Eulerian–Lagrangian simulations with geotechnical centrifuge model test data in dry dense sand. Both approaches consider pre-dented piles with the objective of estimating the soil strength, characterised by the cone resistance, at which minor initial damage will start to propagate. Simplified analysis of structural dent propagation and radial stresses generated in the soil during advance of a deformed pile led to a simple calculation procedure to assess the potential for extrusion buckling. Reasonably good agreement was achieved between the proposed calculation method, numerical simulations and centrifuge tests data, rendering the approach a valuable screening tool for practical application. [ABSTRACT FROM AUTHOR]

In an attempt to promote a cleaner environment, the deployment of waste materials in soil amendment protocols has been a major concern for civil engineers. Recent discoveries in the study of soil mechanics have revealed the pozzolanic tendencies demonstrated by these waste materials, which are beneficial in the development of road infrastructure. This has necessitated the need for this research to document the impacts of exploring the usage of combined solid waste derivatives in ameliorating the geotechnical parameters of deficient soil. The current stabilization exercise was geared towards the improvement of the mechanical properties of soil and surpassing the detrimental tendencies especially caused by seasonal variations. Moving forward, the microstructural response of the unaltered and additive ameliorated soil was investigated via qualitative means such as scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The additives including cement kiln dust (CKD) and rice husk ash (RHA), were added by air-dried weight of the soil and compacted based on the standards of British Standard Light (BSL), West African Standard (WAS) and British Standard Heavy (BSH). With regard to the compaction exercise, the incorporation of these additive materials into the soil facilitated a gradual increase in the maximum dry density (MDDs) followed by a decrease in the optimum moisture contents (OMCs). In view of these research findings, soil treatment studies facilitated a substantial upsurge in the strength (California bearing ratio (CBR) and unconfined compressive strength (UCS)) values of the ameliorated soil, in agreement with the requirements of Nigeria's general specification for all compactive efforts. Finally, the usefulness and efficacy of combining these wastes in deficient soil treatment were validated qualitatively via the SEM and FTIR strategies. The results of the SEM analysis revealed some disparities between the unaltered and altered soil specimens, providing insights into the direction of calcite formation in the additive-treated soil. [ABSTRACT FROM AUTHOR]

Copyright of Tecnología y Ciencias del Agua is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) 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.)

Microbially induced calcite precipitation is a soil improvement technique in which bacteria are used to produce calcium carbonate (biocement), precipitated after the hydrolysis of urea by the urease enzyme present in the microorganisms. This technique is becoming popular, and there have been several real cases of its use; however, the dosages and reaction times used to attain a required percentage of biocement mainly stem from previous experimental tests, and calculations are not performed. Thus, it is fundamental to have more robust tools and the existence of numerical models able to compute the amount precipitated, such as the one proposed in this paper, can be an important contribution. A two-phase porous medium model is created to analyse the precipitation process. The solid phase contains soil particles, bacteria and biocement, while the fluid phase contains water, urea and other dissolved species. A coupled bio-chemo-hydro-mechanical finite element formulation is defined, embodying the biochemical reaction, water seepage, the diffusion of species and soil deformation. The main novelties of this study are as follows: (i) porosity changes are computed considering the generation of solid mass due to biocement precipitation, and, therefore, soil permeability is updated during the calculation, with these highly coupled equations being integrated in time simultaneously and not sequentially; and (ii) the model is calibrated with experimental tests conceived especially for this purpose. The model is then used to compute the biocement precipitated in a sand column simulating a real experimental test. The results of the simulations present a distribution of biocement along the column closer to that observed in the experimental tests, validating the model. [ABSTRACT FROM AUTHOR]

This study investigated the structural and environmental recovery of weathered hydrocarbon-contaminated soils using low-carbon solutions and aimed to ascertain the suitability of the remediated soils for engineering purposes. 25% (w/w) of ground ripe (RPP) and unripe (UPP) waste plantain peels were each added to 1 kg weathered hydrocarbon-contaminated soil samples and monitored for 90 days. Biological, physicochemical, and engineering properties were analysed for all samples in triplicates. After 90 days of remediation, RPP and UPP nutrients degraded the mid-distillate hydrocarbon alkanes by 93% and 88%, while the heavier hydrocarbon alkanes were degraded by 83% and 85%, respectively. The polyaromatic hydrocarbons (PAHs) had 89% and 93% degradation for RPP and UPP-treated soils, respectively, while the natural attenuation sample had 28% degradation. The soil compressive strength increased by 16% and 19% for RPP and UPP-treated soils, respectively, whereas the natural attenuation soil compressive strength remained fairly constant. It was observed that the remediated soil cohesion, angles of internal friction, maximum dry density, and optimum moisture content all improved as the remediation proceeded, which subsequently showed that the remediation influenced the engineering properties of the contaminated soils. Therefore, the remediation of the contaminated soil improved the structural suitability of the soils. [ABSTRACT FROM AUTHOR]

The formation of layering during the sedimentation process of tailings makes it of great significance to investigate tailings and to analyze their susceptibility to flow liquefaction. In this study, homogeneous iron ore tailings (IOTs) specimens were reconstituted with pure coarser grains and pure finer grains sampled from a typical tailings storage facility. Additionally, an improved sample preparation method was developed to create heterogeneous IOTs samples containing a fine-grained interlayer with different thicknesses and dip angles using the above two materials. A series of standard drained and undrained triaxial compression tests were conducted to investigate the effects of the presence of a layered structure and its geometry on the stress–strain responses, and the properties of the IOTs under the critical state soil mechanics framework, which has been widely adopted in the analysis of liquefaction in mine tailings. The results showed that for the two homogeneous specimens, unique critical state lines (CSLs) can be identified, but they have different degrees of curvature in the e-ln p′ plane, causing a decrease in the susceptibility to liquefaction with increasing fines content. With increasing fine-grained interlayer thickness (FGLT) within 0–40 mm, the critical state friction angle (φcs) decreased steadily, while the CSLs in the e-ln p′ plane translated upward. This may be because the morphology of the microstructure within the fine-grained interlayer restricted the compression of the intergranular pores. With increasing fine-grained interlayer dip angle (FGLA) within the range 0–30°, φcs decreased until a discontinuity occurred at a dip angle of 15°, while the CSLs in the e-ln p′ plane rotated clockwise through a pivot point. Different FGLAs could change the contact area between the different layers and the axial distribution of the fine-grained interlayer and thus may further contribute to the rotation of the CSLs. [ABSTRACT FROM AUTHOR]

The persistent trend of rising temperatures and shifting weather patterns caused by climate change has prompted significant concern around the world. This research aims to evaluate the instability of slopes in Almaty, Kazakhstan, under various rainfall patterns, groundwater tables, and slope geometries by incorporating the principles of unsaturated soil mechanics. However, there have been a limited number of studies incorporating the principle of unsaturated soil mechanics with constant rainfall patterns in Central Asia, particularly in Kazakhstan, on the impact of rainfall-causing landslides. Hence, in this research, GeoStudio software (SEEP/W and SLOPE/W) was used to simulate the factor of safety (FoS) and pore water pressure for the investigated slopes under different rainfall patterns. Results from Hyprop and statistical method show that the saturated volumetric water content is 0.502, whereas the residual one is 0.147 and for the permeability function the conductivity coefficient started to sharply decrease at the suction value of 2 kPa when the air-entry value was 24 kPa. Findings from numerical analysis show the change in FoS for the slope of 10mheight and 27-degree slope angle was 6%, 7%, 7%, and 8% for cyclic, delayed, advanced, and normal distributions, respectively. For the slope with 20 m height and the same 27-degree angle, the change in FoS was 8%, 10%, 8%, and 11% for the cyclic, delayed, advanced, and normal distributions, respectively. These same patterns were shown in slopes with 35-degree and 45-degree angles, having the same 10 m and 20 m heights. Comparatively, this shows that slopes under cyclic rainfall patterns (240mmof rain within 12 days) are less prone to failure compared to slopes under continuous, delayed, or regularly distributed rainfall patterns. Moreover, an increase in slope height and angle also affect the FoS negatively. It should be noted that the results obtained are only applicable to clayey-loam soil. [ABSTRACT FROM AUTHOR]

Since aquifers deform under applied stresses, it is important to understand the interaction between fluid flow and soil deformation, as the deformation of the solid matrix affects the storage of water in the void space and may reach an extent that causes land subsidence under certain conditions. Geological heterogeneity has a major influence on groundwater movement and can therefore affect the amount of compaction. The aim of this work is, therefore, to perform a stochastic analysis of the influence of the variability of hydraulic conductivity fields on the interaction between excess fluid flow and soil deformation in heterogeneous, deformable porous media. The stress equilibrium equation and the storage equation together form a pair of coupled constitutive equations to describe the interaction of deformation (volume strain) and excess pore fluid pressure head. Using the Fourier–Stieltjes representation approach and a perturbation approximation, the coupled equations are solved analytically in the Fourier space domain for the case of unidirectional excess mean flow. Based on these solutions and the representation theorem, results are obtained for the variances of excess pore fluid pressure head and volume strain. They serve as an index of variability quantification for the evaluation of the variability of the log conductivity field and the compressibility coefficient of the soil on the variability of pressure head and volume strain fields. An illustration of the application of the proposed stochastic theory to predict the excess pore pressure and volume strain under uncertainty is also given. [ABSTRACT FROM AUTHOR]

To explore the interaction between underwater explosion bubbles and soil–water interface, a near soil–water interface underwater explosion model based on the arbitrary Lagrangian–Eulerian method was established in this work. The peak pressure of the shock wave, maximum bubble radius, and bubble evolution in free-field and bottom-charge underwater explosions determined from the proposed simulation were highly consistent with the experimental results, thereby validating the proposed numerical model. The effects of the explosion distance and amount of explosive charge on the bubble–soil surface interaction were evaluated. The results showed that the reflection coefficient of the soil–water interface was in the range of 1.204–1.250, suggesting that it was hardly affected by the explosion distance and amount of explosive charge. The attenuation coefficient of the saturated soil was found to be 1.058. With the decrease in the explosion distance, the period and maximum radius of the bubbles slightly increased, and soil deformation increased as the lower surface of the bubbles was closer to the soil surface. For explosion distances of 0.3 and 0.4 m, only an overall movement of the soil surface was observed. When the explosion distance was 0.2 m or lower, a powerful downward jet was generated upon the pulsation of the first bubble, resulting in craters and slender depressions in the soil. With the increase in the amount of explosive charge, the period and maximum radius of the bubbles increased, and soil deformation also increased. These findings are expected to help advance our understanding of underwater explosion dynamics. [ABSTRACT FROM AUTHOR]

This study aims to develop a novel vibratory compaction instrument designed for the preparation of large triaxial soil specimens, offering an efficient alternative to the traditional manual specimen preparation process. However, when the motor frequency closely aligns with the natural frequency of the structure, severe resonance phenomena may occur. This paper employed finite element modal analysis, experimental modal analysis, and operational modal analysis techniques to conduct a multi-objective optimization of the structure, aiming to improve the dynamic characteristics. First, the natural frequency and mode shapes of the vibratory compaction instrument were determined via finite element technology. Subsequently, the optimization of this instrument was conducted by integrating the Kriging surrogate model with the Non-dominated Sorting Genetic Algorithm II (NSGA-II). Finally, the steel column underwent a modal test using impulse stimulation to ascertain its natural frequency, and the stochastic subspace identification (SSI) approach was employed to conduct an operational modal analysis of the vibratory compaction instrument to determine its modal characteristics. The experimental findings corroborated the conclusions obtained from the finite element analysis, validating the precision of the finite element modal analysis and the rationality of the optimized structure. The research results are of significant importance for improving the preparation efficiency of large triaxial specimen, contributing to advancements in soil mechanics testing. [ABSTRACT FROM AUTHOR]

In order to explore the applicability of the hardening soil constitutive model for numerical analysis of soft soil underground engineering in the Pearl River Delta region, and based on four different stress path triaxial tests, the mechanical properties and variation of constitutive model parameters of hardening soil were analyzed for the typical silty soil in this region. Research results have shown that lateral unloading and drainage conditions have significantly impact on the partial parameters of constitutive model, such as the strength parameters of c' and φ ', the stiffness parameters such as Eref 50, E ref ur and m, but the impact on the failure ratio Rf is relatively small. For the consolidated undrained lateral unloading condition, the main parameters of the constitutive model for typical silty soil in the Pearl River Delta region are shown as the reference secant modulus Eref 50 is 2.34 MPa, with reference to tangent modulus Eref oed is 1.59 MPa, with reference to the loading unloading modulus E ref ur is 11.67 MPa, with a failure stress ratio of Rf is 0.98, and the power exponent m related to stiffness stress level is 1.84; Among them: Eref 50 is 1.47 times of Eref oed, E ref ur is 7.34 times of Eref oed. The practice of a deep foundation pit of soft soil in the Pearl River Delta has proven that the constitutive model of hardening soil is suitable for simulating the mechanical properties of soft soil in this region. [ABSTRACT FROM AUTHOR]

Soil arching is one of the main load transfer mechanisms of geosynthetic‐reinforced and pile‐supported (GRPS) embankments. This study established a numerical spring‐based trapdoor model that can consider the coupling effect between embankment filling, horizontal geosynthetic, piles, and soft soil between piles by the discrete element method (DEM). The effects of multiple factors on the deformation pattern, load transfer, and the settlement at the top surface of GRPS embankments were analyzed, such as soft soil stiffness, geosynthetic stiffness, fill height, and pile clear spacing. The multiple spring‐based trapdoor (MS‐TD) model effectively replicated the actual deformation of soft soil between piles in engineering practice by elucidating the nonuniform settlement of the fill on the trapdoor. Although the geosynthetic indirectly reduces the load transferred to the pile top by weakening the soil arching, it can directly increase the load transferred to the pile top by the membrane effect, thereby increasing the total load transferred to the pile top. The effect of the geosynthetic on reducing settlement decreases with the increase of soft soil stiffness, and the displacement reduction ratio at the top surface remains unchanged when it exceeds a certain value. In addition, the shape of the soil arch evolves rather than unchanged during the growth of pile clear spacing. [ABSTRACT FROM AUTHOR]

Soluble salts in soil cause changes in soil behaviour, the extent of which varies depending on salinity levels. Salt-induced soil deformation leads to various engineering problems. Na2SO4 is among the most widespread and influential salts. This study focuses on Na2SO4 and investigates its effects on soil strength via a series of triaxial tests performed in the laboratory. The study examines different levels of salt and moisture content. Additionally, the study investigated the soil mechanism through its meso and micro structure. The research indicates that the impact of salinity on soil strength is modulated by moisture content. In situations where moisture content is low, salinity markedly affects the soil strength; however, as moisture content increases, the impact of salinity on soil strength decreases. Salinity alters the shape, size and orientation of soil particles, resulting in modifications to the interparticle and charge forces. This ultimately leads to changes in the soil strength parameters. [ABSTRACT FROM AUTHOR]

Enzyme induced carbonate precipitation (EICP) is a new bio-cementation technique that utilizes plant-sourced urease to catalyze urea degradation and reaction with calcium iron, resulting in the formation of calcium carbonate (CaCO3) for soil improvement. EICP has considerable promise for novel and sustainable engineering applications such as soil strengthening, pollutant remediation, and other in situ field applications. In this study, the effect of EICP on the geotechnical characteristics of expansive soil is examined. A series of laboratory tests have been performed with an optimal concentration ratio of 0.75 mol/L. The outcomes of the compaction experiment indicated a slight increment in the dry density of the expansive soil from 15.78 to 16.71 kN/m3.Further, it diminished the optimal moisture content of the soil, decreasing it from 22.3 to 18.5%. The utilization of EICP improves the soil mechanical characteristics, reducing swelling pressure by 80% and increasing the UCS, cohesion, friction angle, unsoaked and soaked CBR by 66%, 44%, 49%, 441%, and 430%, approximately. Additionally, it leads to a significant decrease in soil permeability, approximately 63%. Moreover, SEM and XRD analysis confirmed the presence of CaCO3 content in the treated soil. The experimental findings indicated that the EICP method holds promise in enhancing expansive soil within engineering projects. [ABSTRACT FROM AUTHOR]

With the increasing demand for large and deep anchor projects in soft soil areas, issues related to settlement in circular foundation pits and damage to supporting structures have become significantly pronounced. The absence of pertinent design methods significantly impacts construction safety. Through on-site monitoring and statistical analysis, this study examines the spatiotemporal evolution of deformation in circular foundation pits, the deformation characteristics of retaining structures, and surface settlement features. Key design factors influencing the stability of circular foundation pits are explored. The research indicates that structural deformation and surface settlement are closely related over time and exhibit substantial spatial coordination. The deformation control capability of circular foundation pits is considerably stronger than that of square foundation pits, and it is less influenced by excavation depth. Diameter and soft soil thickness have a substantial impact on structural deformation and surface settlement. When the diameter is less than 40 m, the structural deformation remains below 0.1%. The study establishes an evaluation method for the deformation control of large and deep circular foundation pits in soft soil based on a significant amount of engineering monitoring data. It categorizes deformation control indicators for pit excavation based on different design factors, offering reliable theoretical support for relevant design professionals. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study on the investigation of microscopic mechanism governing the interaction of woven geotextile and angular sand employing the 3D discrete element method (DEM). The surface texture and tensile properties of the geotextile were simulated using overlapping spherical particles, and the angular sand was simulated using rigid blocks. The DEM models were fully calibrated based on previous experimental data. The shear and dilation zones of sand near the interface were quantitatively determined based on particle displacement gradients. Analysis of contact forces was conducted to explain the microscopic mechanism behind the macroscopic strength evolution. The influence of geotextile surface roughness on the shear strength of the geotextile-sand interface is also discussed. The results show that the failure mode of the woven geotextile-sand interface is a combination of particle sliding failure along the geotextile surface and shear failure of the sand within the shear zone above the interface. There is a rapid redistribution of contact forces prior to reaching peak shear resistance, and the average normal contact force within the shear zone remains relatively constant after the peak shear stress is achieved. A completely developed shear zone stabilizes soil deformation, typically after achieving the peak shear resistance. • The thickness of the stabilized shear zone decreases as the normal stresses increase. • The shear zone is completely developed after the peak shear resistance is reached. • Contact forces are rapidly redistributed prior to reaching peak shear resistance. • The evolution of shear strength is caused by interparticle sliding in the shear zone. [ABSTRACT FROM AUTHOR]

Several tailings dam failures have highlighted the potential for instability under prevailing drained conditions, which can be represented in the laboratory using constant shear drained (CSD) loading. In this study, the mechanical response of three mine tailings gradations (coarse, intermediate, and fine) from a tin ore tailings storage facility subjected to CSD loading were evaluated. The experimental results were interpreted using the critical state soil mechanics framework and different instability criteria. Salient findings include the following: (1) the onset of instability in initially loose specimens was dictated by a tradeoff of volumetric strain components (i.e., elastic and plastic), which in turn governed the evolution of the dilatancy and plastic modulus, key properties for modern constitutive models that were also investigated in this study; (2) dense-type instabilities may occur for initial states above the critical state line; this response was observed in the fine tailings due to their compressibility and initial state before CSD stress relief; (3) variable rate tests suggested that drained creep in the intermediate tailings made the second-order work instability criterion unattainable; variable rate effects were manifested in the postinstability responses of the intermediate and fine tailings but not in those of the coarse tailings; and (4) existing instability criteria perform similarly when applicable, but they also have limitations. In this context, a new criterion is proposed by modifying an existing criterion. This study advances the understanding of the mechanical response of mine tailings, under nonstandard stress paths. [ABSTRACT FROM AUTHOR]

Evaluation of the liquefaction susceptibility of soils is one of the most important subjects in geotechnical earthquake engineering. The energy-based liquefaction evaluation procedure, with a focus on seismic energy propagation and dissipation in soils, has attracted increasing attention in recent years. This paper presents a systematic analysis of cyclic triaxial test data of three series of silty sands through the energy-based approach. The stress-normalized accumulative dissipated strain energy per unit volume required for triggering liquefaction is used to evaluate the liquefaction potential of sands. It is a function of void ratio, fines content, and sand type. The pore pressure generation with the stress-normalized accumulative dissipated energy per unit volume can be simulated by a one-parameter pore pressure model, and the model parameter is affected by void ratio, fines content, and sand type. Unified characterizations of the stress-normalized accumulative dissipated energy per unit volume required for liquefaction and the fitting parameter of the pore pressure model are proposed in the framework of critical state soil mechanics. [ABSTRACT FROM AUTHOR]

Geomechanical and heat transfer characteristics of gas hydrate-bearing sediment (GHBS) are significantly affected by hydrate dissociation during gas production from reservoirs, which is typically tens of meters in thickness. This paper presents the development of an innovative in-flight apparatus that is capable of modeling hydrate dissociation in GHBS on a geotechnical centrifuge, by which a series of model tests are conducted under normal gravity (1g) and hypergravity (100g and 80g). The effects of the hypergravity field on the development of pore pressure, soil deformation, as well as particle migration and gas production during hydrate dissociation are explored. Results show that gas released from hydrate dissociation increases excess pore pressure and changes the soil pore structure. During hydrate dissociation, the accumulation of excess pore pressure leads to the development of gas-driven fractures and the subsequent formation of a dominant seepage channel. The critical excess pore pressure of fracture formation in the 100g test is higher than that in the 1g test. The dominant seepage channel promoting fluid seepage and fine particle migration is more likely to be formed into obvious fracture structures under 100g compared with slender pipe structures under 1g. Two peaks are witnessed in gas production in the 100g test, corresponding to the stage at maximum pressure difference and at the complete formation of dominant seepage channels, which is consistent with that in the field trails. These results indicate that the formation of fracture during hydrate dissociation is beneficial to efficient gas production, while the problem of particle migration should be carefully paid attention to. [ABSTRACT FROM AUTHOR]

Accurate prediction of soil liquefaction is important for preventing geological disasters. Soil liquefaction prediction models based on machine learning algorithms are efficient and accurate; however, some models fail to achieve highly precise soil liquefaction predictions in certain areas because of poor generalizability, which limits their applicability. Thus, a soil liquefaction prediction model was constructed using the CatBoost (CB) algorithm to support categorical features. The model was trained using standard liquefaction datasets from domestic and foreign sources and was optimized with Optuna hyperparameters. Additionally, the model was evaluated using five evaluation metrics and its performance was compared to that of other models that use multi-layer perceptron, support vector machine, random forest, and XGBoost algorithms. Finally, the prediction capability of the model was verified using three case studies. Experimental results demonstrated that the CB-based model generated more accurate soil liquefaction predictions than other comparison models and maintained their performance. Hence, the proposed model accurately predicts soil liquefaction and offers strong generalizability, demonstrating the potential to contribute toward the prevention and control of soil liquefaction in engineering projects, and toward ensuring the safety and stability of structures built on or near liquefiable soils. [ABSTRACT FROM AUTHOR]

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Layered structures comprising coral sand and gravel have been observed in hydraulic filled foundations in the coral reefs in the South China Sea, leading to anisotropy in their physical and mechanical properties. However, the effect of a layered structure on the strength and deformation of the coral soil foundation remains unclear. In this study, a series of large-scale triaxial compression tests and step-loading tests were carried out on four types of samples, i.e., clean coral sand, clean coral gravel, sand-over-gravel layered sample, and gravel-over-sand layered sample, to investigate the impact of confining pressure and the layered structure on the strength and failure modes of these soils. The results indicate that the stress–strain relationships of all samples predominantly exhibit strain hardening under drained conditions. Under identical confining pressures, the peak strength of clean coral sand is the lowest, while that of coral gravel is the highest. The peak strengths of the two layered samples fall between these extremes, with the gravel-over-sand layered sample exhibiting higher strength. All four samples have similar peak friction angles, slightly exceeding 40°. The difference in peak strength among the four types of samples is attributed to the variations in cohesion, with the cohesion of clean coral gravel being up to four times that of clean sand, and the cohesion of layered samples falling between these two. Both clean sand and clean gravel samples exhibit a bulging phenomenon in the middle, while the layered samples primarily exhibit bulging near the coral gravel layer. In the step-loading tests, the bearing capacity of the layered samples falls between those of clean coral sand and coral gravel, with the gravel-over-sand layered samples demonstrating higher strength. Moreover, the p-s curve of the gravel-over-sand layered samples obtained from the large-scale triaxial apparatus under a confining pressure of 400 kPa resembles that from the plate load tests on the same samples. [ABSTRACT FROM AUTHOR]

The straight part of the corrugated steel plate (CSP) pipe-arch structure in soil may cause local buckling instability due to insufficient load-bearing capacity. Recently, composite CSP pipe-arch has been widely utilized to enhance structural stability, and their stability needs to be thoroughly investigated. This paper studies the local buckling stability problem of the straight part of composite CSP pipe-arch in soil by simplifying the soil support and introducing the inter-layer bonding effect. Based on elastic stability theory, a theoretical mechanical model of composite CSP pipe-arch was proposed. The Rayleigh–Ritz method and the semi-combined composite structure stiffness approximation were used to derive the critical buckling conditions for the straight part of the composite CSP pipe-arch. Through numerical calculation and influencing factors analysis, it is concluded that the critical buckling load of the straight part of the composite CSP pipe-arch structure is affected by the elastic modulus, thickness, Poisson's ratio, rotational restraint stiffness and side length of the straight part of the material. In particular, it is found that as the inter-layer bonding coefficient increases, the critical buckling load is improved, while the critical buckling wave number is mainly influenced by the width of the straight part, elastic modulus, and inter-layer bonding coefficient. Additionally, we discussed the coupling effect of several key parameters on the stability of the structure. The results of this study offer theoretical foundations and guidance for the application of composite CSP pipe-arch in soil engineering, such as culverts, tunnels, and pipeline transportation. [ABSTRACT FROM AUTHOR]

The carrying-soil effect is an important factor affecting the success or failure of rectangular pipe jacking construction. Because it is difficult to explore the dynamic evolution process of the carrying-soil effect in the field test, this paper relies on the pipe jacking project of a comprehensive pipe gallery in Suzhou City, and uses ABAQUS 2021 finite element software to simulate the jacking process of rectangular pipe jacking. Based on the theory of plastic mechanics of rock and soil and the related research and application status, the equivalent plastic strain index is introduced as the basis for judging the failure boundary of soil in the numerical simulation results, and the boundary between the carrying-soil area and the surrounding soil is determined, that is, the shear fracture surface. According to the principle of plastic potential energy, the development direction of the fracture surface is consistent with the direction of plastic flow, so as to predict the development direction of the boundary of the carrying-soil area. According to the change in the equivalent plastic strain cloud map with the jacking mileage, the evolution process of the carrying-soil effect is clarified, and the dynamic evolution law of the carrying-soil area is revealed, which is of great significance for predicting the disturbance of the surrounding soil during the construction of rectangular pipe jacking and accurately evaluating the environmental effect of the construction. [ABSTRACT FROM AUTHOR]

Due to its inherent advantages, shield tunnelling has become the primary construction method for urban tunnels, such as high-speed railway and metro tunnels. However, there are numerous technical challenges to shield tunnelling in complex geological conditions. Under the disturbance induced by shield tunnelling, sandy pebble soil is highly susceptible to ground loss and disturbance, which may subsequently lead to the risk of surface collapse. In this paper, large-diameter slurry shield tunnelling in sandy pebble soil is the engineering background. A combination of field monitoring and numerical simulation is employed to analyze tunnelling parameters, surface settlement, and deep soil horizontal displacement. The patterns of ground disturbance induced by shield tunnelling in sandy pebble soil are explored. The findings reveal that slurry pressure, shield thrust, and cutterhead torque exhibit a strong correlation during shield tunnelling. In silty clay sections, surface settlement values fluctuate significantly, while in sandy pebble soil, the settlement remains relatively stable. The longitudinal horizontal displacement of deep soil is significantly greater than the transverse horizontal displacement. In order to improve the surface settlement troughs obtained by numerical simulation, a cross-anisotropic constitutive model is used to account for the anisotropy of the soil. A sensitivity analysis of the cross-anisotropy parameter α was performed, revealing that as α increases, the maximum vertical displacement of the ground surface gradually decreases, but the rate of decrease slows down and tends to level off. Conversely, as the cross-anisotropy parameter α decreases, the width of the settlement trough narrows, improving the settlement trough profile. [ABSTRACT FROM AUTHOR]

The stability of underground diaphragm walls is crucial for ensuring the safety and integrity of trench excavations in geotechnical engineering. This study addresses this critical issue by proposing a novel destabilization mechanism based on a sliding body model specifically designed for diaphragm wall trenching operations. The research employs an analytical framework rooted in soil mechanics and plasticity theory, utilizing limit equilibrium analysis to develop a method for calculating the minimum required slurry density and corresponding safety factor for trench stability. The study compares two distinct approaches to slurry density computation, analyzing their sensitivity to various influencing factors. Theoretical findings are validated through multiple real-world engineering case studies. Comparative analysis demonstrates the superiority of the proposed method, particularly in assessing trench stability within clay layers. Key variables influencing the safety factor are identified, including trench length, slurry density, soil friction angle, and the relative height difference between slurry and groundwater levels. Results indicate that actual slurry densities observed in practice consistently fall within the bounds predicted by the theoretical calculations. This research contributes a valuable theoretical framework to the field of diaphragm wall construction, offering improved accuracy in stability assessments and potentially enhancing safety in geotechnical engineering projects. [ABSTRACT FROM AUTHOR]

Landslides are common geological hazards that cause significant losses. Anti-slide piles are commonly used in landslide engineering, and model testing is one of the means to study pile-supported structures. However, model tests face several challenges, including difficulty in controlling the experimental process, challenges in repeated tests, and difficulty in monitoring soil deformation around piles. To address these issues, this study presents a model test method using particle image velocimetry (PIV), transparent soil, and 3D printing technology. Using this method, a series of model tests were conducted, including single-row and double-row anti-slide piles. The experimental results indicate that, compared with single-row piles, double-row piles exhibit better supporting effects. In the pile‒soil interaction, the displacement of the extrusion of soil between piles was controlled under the combined action of the front and back rows of piles. The inclination angle of a single-row pile after the test was 8°, whereas that of a double-row pile was reduced by 62.5%. With respect to the displacement of the soil behind the piles, the phenomenon of a "displacement triangle" behind the piles was observed. An analysis of the change process in this area revealed that the relative displacement caused by pile‒soil interactions is mainly distributed in the surface layer of the soil. The experiments demonstrate that this system is suitable for pile-supported structure model tests. [ABSTRACT FROM AUTHOR]

Structurally controlled slope failure in open-pit mining occurs when the shear stress acting on the geological structure exceeds its shear strength. Mining slope stability is an extremely important topic from the ramifications of safety, social, economic, environmental and regulatory factors. This study reports the engineering geological setting of a bedded mining slope in China, and evaluates its stability via a numerical approach. First, a slope profile model is constructed using a synthetic rock mass (SRM) modeling approach. More specifically, the mechanical behavior of colluvium, intact rock and discontinuities are represented by linear contact model, bonded particle model and smooth joint model, respectively. Then, the factor of safety (FOS) and instability process are investigated by integrating the discrete fracture network (DFN)-distinct element method (DEM) and strength reduction technique (SRT). In addition, shear stress analyses of colluvium and bedrock are conducted for revealing the potential failure mechanism. Finally, the well-established limit equilibrium (LEM) and finite element method (FEM) are adopted for simulation results comparison and validation. [ABSTRACT FROM AUTHOR]

Oil pipeline projects in China are mostly long‐distance, linear projects, making pipelines vulnerable to safety problems. Consequently, pipeline monitoring is crucial for their effective maintenance. In this study, a recently developed optical fiber sensing technology was employed to monitor pipeline crossing projects and conduct tests to study the coordination deformation of buried‐pipeline‐soil systems using a comprehensive deformation monitoring system model based on optical fiber sensing technology developed for the test. The test realized three‐dimensional monitoring of the pipeline and soil deformation when lateral displacement occurred in the soil. In addition, the feasibility of monitoring the deformation of different encapsulation types of optical fiber gratings and different sheath types of distributed optical fibers was demonstrated using this test model. The test results showed that both distributed optical fibers and fiber Bragg gratings (FBGs) could effectively reflect the strain distribution status of a pipeline during deformation monitoring. However, distributed optical fibers could detect data between two points, making them more suitable for pipeline monitoring. The FBG displacement and soil‐pressure gauges could effectively monitor pipeline displacement and soil‐pressure changes, thereby providing a basis for predicting the direction of slider movement during pipeline deflection and landslide monitoring. This test realized the multiparameter monitoring of pipeline deformation, pipeline displacement, and soil pressure along the pipeline, thereby providing a theoretical basis for developing prediction and warning systems for buried pipelines. [ABSTRACT FROM AUTHOR]

Based on the Xiaolangdi North Bank Irrigation Area Project, this study combines numerical simulation and BP neural network methods to investigate the sensitivity of tunnel soil and its parameter inversion under continuous heavy rainfall. The research results indicate that changes in water-level and soil strength parameters have a significant impact on the deformation of tunnel surrounding rock. By comparing the sensitivity factors of different parameters, the main parameter sensitivities affecting the displacement of tunnel surrounding rock were determined to be water level, internal friction angle, and cohesion. The mechanical characteristics of the tunnel construction process were analyzed using finite difference method numerical analysis software FLAC3D, and the results were used as a sample dataset for inversion analysis. Through neural network inverse analysis based on orthogonal design method, the cohesion and internal friction angle of loess layer ④, loess layer ④-1, and loess layer ⑤ were determined, and the data of groundwater level elevation were obtained. Field applications proved the effectiveness and rationality of this method. [ABSTRACT FROM AUTHOR]

Objective: To explore the mechanical properties of weak expansive soil under different moisture contents and confining pressures. Methods: The triaxial remolded soil samples with different moisture contents (14%, 16%, 18%, and 20%) were prepared for the obtained Nanyang weak expansive soil. Four groups of 16 consolidated drained triaxial shear tests with a confining pressure of 50, 100, 200, and 300 kPa were carried out to study the effects of confining pressure and water content on the deviatoric stress and pore pressure of weak expansive soil with strain. Results: The study showed that the shear strength of weak expansive soil samples gradually increased with the increase of the water content, but its increase nonlinearly decreased as the confining pressure increased. When the axial strain was small, the pore pressure significantly increased, and the pore pressure increased tended to be stable slowly and gradually as the axial strain gradually increased. Therefore, the research results could be used to avoid the diseases caused by the characteristics of weak expansive soil in engineering construction and provide theoretical references for improving engineering foundations in weak expansive soil areas. [ABSTRACT FROM AUTHOR]

The mechanical behavior of silty sands is a crucial topic in the field of soil mechanics. However, many studies have been conducted to determine the main features of silty sand mixtures, there are some mechanisms that remain unclear. Most of the previously applied studies have focused on the behavior of silty sands under conventional paths, such as consolidated drained and consolidated undrained stress-strain paths. Recent investigations have shown the assumption that the mentioned conventional paths are critical for all situations is not accurate. Therefore, considering partially drained paths cannot only help better understand the mechanical behavior of silty sands but is also necessary to ensure the safety of projects. In this paper, 14 triaxial shear tests are applied to assess the effects of partially drained paths on the main features of the shearing mechanism of silty sands. As the water inlet is the most critical path between the partially drained tests, this research is done by considering only this type of partial drainage and ignoring other non-crucial partially drained strain paths. Achieved results indicate that partial drainage can affect the behavior of samples with a little fine content (up to 5%) significantly, while for samples with more fine content, these effects are not considerable. In other words, samples that do not exhibit a fully static liquefaction (completely softening behavior), will be considerably affected by partial drainage. Effects of water inlet during shearing on the asymptotic stress ratios, excess pore water generation, and experienced stress paths are investigated as well. [ABSTRACT FROM AUTHOR]

Dispersive soils, characterized by their poor resistance to water erosion and high sodium ion concentrations, pose a significant threat to both engineering and agricultural activities. Thus, the identification and improvement of dispersive soils are of paramount importance. There are several theories regarding the causes of soil dispersion, with the prevailing view attributing it to the expansion of the electrical double layer induced by sodium ions, which subsequently reduces the cohesion between soil particles. As a result, sodium indicators such as exchangeable sodium percentage (ESP), percentage sodium (PS), and sodium adsorption rate (SAR) are commonly employed in the identification of dispersive soils. Currently, in efforts to improve dispersive soils for both engineering and agricultural purposes, chemical and biological agents are being added to enhance the soil's erosion resistance and regulate the concentration of sodium ions. Although numerous reviews have been conducted on the identification and improvement of dispersive soils, they tend to focus on the identification methods and the types of improvers, often overlooking the applicability of identification methods, the economic costs and environmental impacts of improvers. In practical improvement, the accuracy of soil identification must be ensured first and foremost. The selection of improvers should not only prioritise efficacy but also undergo thorough analysis and evaluation from multiple perspectives. This paper, therefore, reviews the advantages and disadvantages of various identification methods and assesses the differences among improvers from economic and environmental standpoints, providing a comprehensive theoretical basis for the improvement of dispersive soils. [ABSTRACT FROM AUTHOR]

Deep water poses challenges for conventional surface conductors due to soft seabed soil. The current installation methods are time-consuming and risky, leading to sinking and instability. A new high-bearing capacity surface conductor is essential. This study investigates lateral bearing characteristics of deepwater expandable surface conductors. A mechanical model was established based on fundamental mechanics principles. Three types of expandable conductors were designed, varying expansion material distribution. The study compares lateral bearing characteristics, analyzes changes in bearing capacity based on soil parameters and expansion material section, and demonstrates enhanced bearing capacity of the new conductors compared to traditional ones. This research supports expandable surface conductor design and numerical simulations in surface well construction. [ABSTRACT FROM AUTHOR]

Structural changes of soil-type media are known to occur with the structural destruction of soil bonds and the rock mass skeleton. Thus, structural destruction of the soil and rock mass affects the mechanical and strength parameters of the soil. Using existing experimental data and principles of building models of deformation of a continuum, an equation of state of shear deformation of soil and rock mass is obtained accounting for structural changes. A parametric analysis of the proposed model of deformation of soils is carried out and the applicability of the model in practical tasks is demonstrated. The use of the proposed model of deformation allows us to theoretically determine the terms and methods of failure and crushing of soils and rock mass under different types of loading. [ABSTRACT FROM AUTHOR]

This study investigates the correlation between the California Bearing Ratio (CBR) and the Dynamic Cone Penetrometer (DCP) for subgrade soil analysis. The paper aims to provide practical equations for predicting CBR values from DCP test results, therefore enhancing the efficiency of soil assessments in engineering practice. By analyzing test data and proposing correlations for different soil groups, the study introduces recalibrated correlations that demonstrate high accuracy in predicting CBR values. The newly proposed equations offer reliable predictions with R 2 values of 0.89, 0.92, and 0.94 for clean sand, silty sand or sandy silt, and cohesive soil, respectively. These correlations serve as valuable tools for engineers, enabling rapid and accurate CBR estimations for improved decision-making in various engineering projects. [ABSTRACT FROM AUTHOR]

The discrete element method (DEM) has been extensively utilized to investigate the mechanical properties of granules, particularly their microscopic behavior, overcoming limitations in field tests such as cost, time consumption, and soil condition restrictions. To ensure the development of reliable DEM simulations, proper contact model selection and parameter calibration are essential. In this research, a DEM parameter calibration method that could represent the nonlinear relationship between clayey soil pressure and sinkage at different moisture contents was proposed. Firstly, the sinking modulus K and the soil deformation exponent n were identified to reflect the nonlinear pressure–sinkage relationship. Then, sensitive DEM parameters on the soli pressure–sinkage relationship were investigated and calibrated, and the effect of moisture content on them was explored. Finally, the transfer of soil internal stress during subsidence was analyzed using the constructed discrete element model. The average error of the sinking modulus K and the soil deformation exponent n between the DEM and the experimental result at four moisture contents were 4.7% and 4.9%, respectively. The relative error of soil internal stress between simulation and experiment was 6.7%, 4.4%, and 9.7% at depths of 50 mm, 100 mm, and 150 mm, respectively. The soil particle trajectory, soil internal stress distribution, and variations during plate pressure–sinkage progress were analyzed by the constructed DEM model. The results demonstrated good agreement with theoretical models and experimental findings. The proposed clayey soil DEM modeling process that considers the pressure–sinkage nonlinear relationship at different moisture contents can be applied in machine-soil research. [ABSTRACT FROM AUTHOR]

Due to the overexploitation of deep groundwater, the largest cone of depression in the world has formed in the North China Plain. This led to severe geological hazards, including land subsidence and ground fissures, and also caused economic losses. The prevention and treatment of subsidence needs to rely on the accurate prediction of subsidence amount. According to the one‐dimensional consolidation theory and effective stress principle, combined with stratum structure, groundwater flow, stress distribution, and so forth, the high‐pressure consolidation test results of 569.6 m deep borehole soil samples are adopted; with a specific focus on stress and deformation parameters under exploitation of groundwater condition, the soil‐water coupling prediction model of groundwater level lowering depth and land subsidence has been established. Verification with measured subsidence data near the study sites demonstrated that the predicted curve is consistent with the measured one and the differences between them are acceptable. The model can be applied in different areas after making adjustment based on different regional stratigraphic structures. Its key advantage lies in the ability to provide land subsidence prediction for areas lacking monitoring data, making it highly valuable for widespread application. Practitioner Points: There is a compressible stratum structure; it is the internal factors of land subsidence.The groundwater level decline causes the soil body stress to change. It is land subsidence of the external factors.Based on the one‐dimensional consolidation theory and by combining stratigraphic structures, groundwater flow, and stress distribution, a ground settlement prediction model was established. [ABSTRACT FROM AUTHOR]

A comprehensive analysis of the evolutionary dynamics of soil arches is crucial for accurately predicting soil deformations above sinkholes and assessing stability of underground structures. In this study, a series of trapdoor tests were conducted to investigate the progressive development of soil arching in dense sand. The particle image velocimetry (PIV) technique was utilized to capture soil deformation patterns, while fiber optic strain sensing cables were used to validate the displacement influence zone of soil by measuring strain profiles of the foundation. The ground reaction curves, derived from the measurements of earth pressure cells, shed light on the evolution process of stress redistribution and the rotation of principal stresses. The test results reveal that the formation of soil arching alters the overlying pressure on the trapdoor, transferring loads from yielding soil to adjacent stationary soil. The development of soil failure surfaces corresponded with vertical stress variations on the trapdoor. The strain profiles exhibited a characteristic trough above the trapdoor, along with double peaks at its edges. The measurements of micro-anchored strain sensing cables with small anchor spacings provided more accurate distributions of soil shear deformation. Furthermore, the orientation and magnitude of soil arching was inferred from principal stress rotations. The insights gained in this study are valuable for understanding the propagation of soil arching, offering potential implications for the execution of rational geotechnical design and the mitigation of related geological hazards. [ABSTRACT FROM AUTHOR]

In the present study, the undrained cyclic behaviour of biotreated sands using microbial and enzyme-induced carbonate precipitation was investigated for a wide range of initial void ratio after consolidation ( e 0 ), initial effective normal stress ( σ N 0 ′ ) and calcium carbonate content (CC) under direct simple shear (DSS) testing conditions. The critical state soil mechanics framework for untreated sand was first established using a series of drained and undrained (constant volume) tests, which served as a benchmark for evaluating the undrained cyclic liquefaction behaviour of untreated and biotreated sands. The results indicated that the modified initial state parameter ( ψ m 0 ) in DSS condition showed a good correlation with instability states and phase transformation under monotonic shearing. In undrained cyclic DSS loading condition, samples displayed cyclic mobility indicated by an abrupt accumulation of large strain or σ N 0 ′ transiently reaching zero or a sudden build-up of excess pore water pressure. The linkage between static and cyclic liquefaction was established for untreated and biotreated sand specimens based on the equivalence of characteristic soil states. The number of cycles before liquefaction (NL) for the biotreated sand specimens was mainly controlled by the cyclic stress ratio, e 0 , σ N 0 ′ and CC. For a similar initial state prior to undrained cyclic loading, the biotreated specimens required a larger NL compared to the untreated sand. The cyclic resistance ratio at NL = 15 (CRR15) increased with decreasing ψ m 0 for the untreated sand, while the CRR15 for biotreated sand increased with increasing CC and decreasing σ N 0 ′ . [ABSTRACT FROM AUTHOR]

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]

This study utilised the principles of soil mechanics and the physiograph concept to establish pedo-geotechnical patterns of natural soils for the design of pavement structure. A total of 60 disturbed and undisturbed subgrades were sampled from 10 locations at the SB segment, 10 locations through the TZ and 10 locations at the BC end. A series of specific gravity, grain-size distribution, consistency limits, compaction characteristics (unsoaked and soaked CBR) and shear strength parameters were performed. Field observation and test results revealed that the studied area consists of extensive sand, interposed with clayey sand bodies along the SB segment. Also, particles of various sizes at the TZ and heterogeneous sandy clay in the BC segment were noted. Soils from the TZ under soaked conditions have the highest CBR (80.0–88.1%), MDD (19.0–19.1 kN/m3) and the lowest OMC (10.2–10.5%) values. They also have the highest cohesive strength (72.0–80.0 kN/m2) and angle of internal friction (14°−16°). Comparison among properties revealed that soils from the SB area especially, the TZ have much higher subgrade ratings compared to the soils from the BC terrain. The result revealed that the physiography factors affect the performance of the entire pavement structure. [ABSTRACT FROM AUTHOR]