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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]

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]

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]

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]

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]

Buried pipelines subjected to permanent ground deformations (through, e.g., earthquake-induced liquefaction or fault rupture) often experience widespread damage. Regardless of the direction of ground movement, pipelines tend to respond and experience damage axially due to their directional stiffness characteristics. In addition, case studies and previous testing have shown that damage is concentrated at the pipe joints due to their lower strength compared with a pipe barrel. Previous testing has also shown that axial forces increase significantly when pipe connections have jointing mechanisms, such as coupling restraints, with larger diameters than the pipe barrel alone. These enlarged joints act as anchors along the pipe, increasing the soil resistance at these locations. Current methods for predicting the axial force along a pipe underpredict the force demands and oversimplify the mechanics of soil resistance on the joint face. This study conducts a series of 12 pipe-pull tests in a centrifuge, varying joint diameter and burial depth, to quantify the axial forces developed. A strong linear correlation was observed between the soil resistance on a joint face and the joint surface area and burial depth. The study also proposes an analytical solution based on pullout capacity design equations for vertical anchor plates as a function of soil and pipe joint properties. The proposed solution to calculate joint resistance is in good agreement with the centrifuge tests performed for this study and previous full- and model-scale experiments. The proposed prediction equation is anticipated to have future applications to other buried structures because it is based on mechanisms of passive resistance commonly encountered in underground structures and lifelines. [ABSTRACT FROM AUTHOR]

Disposal of municipal solid waste is a significant environmental issue that has detrimental effects on both the environment and human life. The selection of landfill sites is critical and essential to implementing a comprehensive waste management strategy. This study optimizes the selection of landfill sites in Kuwait through the use of overlay analysis and Geographic Information System in conjunction with multi-criteria decision analysis. The study analysis takes into account human, physical economical, environmental, and governmental factors. Seven optimal locations are depicted on the resulting suitability map, each occupying 10 square kilometres or more and have the capacity to handle solid waste for at least one decade per site, considering the current reported waste generation rate. Furthermore, results of a preliminary geotechnical investigation encompassing field and laboratory tests conducted on soil samples collected at one of the proposed sites are presented. The characterization of the retrieved samples included major geotechnical parameters that are of concern in landfill design and siting studies. The results indicate that the soil at the proposed site exhibited low values of hydraulic conductivity, ranging between 3.50 X 10−07 and 8.96 X 10−08 cm/sec, confirming its suitability for siting landfills. There is an urgent need to develop and implement an integrated waste management system in Kuwait. By leveraging the findings of this study, policymakers and governmental authorities can optimize their decision-making procedures to ensure more effective site selection. This approach will significantly reduce contamination risks and enhance sustainability, leading to a more environmentally responsible waste management system in the country. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office 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.)

In order to predict the ground settlement in a scientific, intuitive, and simple way, based on the theory of Bio-consolidation, a three-dimensional fluid-solid coupled numerical calculation programme FGS-3D for ground settlement was compiled by using the Fortran 95 language, and a front-end operation platform was developed by using Microsoft VisualBasic, so that a three-dimensional variable-parameter fully coupled viscoelastic-plastic model of ground settlement was constructed using the city of Yancheng as an example, and the development of ground settlement and horizontal displacement changes from 2021 to 2030 were predicted. The results show that the three-dimensional fully coupled finite-element numerical model of building load, groundwater seepage, and soil deformation established by the above computer development program can directly create a hydrogeological conceptual model of groundwater mining and predict ground settlement, so as to achieve the visualisation of the three-dimensional seepage of groundwater and the fully coupled simulation of ground subsidence in the whole process of groundwater mining. Under the joint action of construction load and groundwater mining, the water level of the aquifer in Yancheng City rises by 1.26 m on average in the main groundwater mining area of the group III pressurised aquifer, forming two smaller landing funnels, and the lowest water level of the two landing funnels is −15 m. [ABSTRACT FROM AUTHOR]

Given the critical role of true triaxial strength assessment in underground rock and soil engineering design and construction, this study explores sandstone true triaxial strength using data-driven machine learning approaches. Fourteen distinct sandstone true triaxial test datasets were collected from the existing literature and randomly divided into training (70%) and testing (30%) sets. A Multilayer Perceptron (MLP) model was developed with uniaxial compressive strength (UCS, σ c ), intermediate principal stress ( σ 2 ), and minimum principal stress ( σ 3 ) as inputs and maximum principal stress ( σ 1 ) at failure as the output. The model was optimized using the Harris hawks optimization (HHO) algorithm to fine-tune hyperparameters. By adjusting the model structure and activation function characteristics, the final model was made continuously differentiable, enhancing its potential for numerical analysis applications. Four HHO-MLP models with different activation functions were trained and validated on the training set. Based on the comparison of prediction accuracy and meridian plane analysis, an HHO-MLP model with high predictive accuracy and meridional behavior consistent with theoretical trends was selected. Compared to five traditional strength criteria (Drucker–Prager, Hoek–Brown, Mogi–Coulomb, modified Lade, and modified Weibols–Cook), the optimized HHO-MLP model demonstrated superior predictive performance on both training and testing datasets. It successfully captured the complete strength variation in principal stress space, showing smooth and continuous failure envelopes on the meridian and deviatoric planes. These results underscore the model's ability to generalize across different stress conditions, highlighting its potential as a powerful tool for predicting the true triaxial strength of sandstone in geotechnical engineering applications. [ABSTRACT FROM AUTHOR]

The helical anchor foundation is driven into the soil under the combined action of torque and vertical pressure. The installation process involves a significant deformation of the soil, which is difficult to simulate numerically using the traditional finite element method. As a meshless method, Smoothed Particle Hydrodynamics (SPH) is very suitable for simulating large deformation problems. In this paper, the SPH meshless method and traditional finite element method are used to simulate the installation and pulling process of helical anchor foundations in sandy soil. The variations in installation force, installation torque, ultimate uplift capacity, and torque correlation factor under different advancement ratios were studied. The research results indicate that using a low advancement ratio for installation can significantly reduce the installation force and torque of the helical anchor and positively affect the ultimate uplift capacity. Moreover, the torque correlation factor is also influenced by the advancement ratio. Using the torque correlation factor value obtained from the "pitch matching" installation to predict the ultimate uplift capacity at other advancement ratios may result in an overestimation. [ABSTRACT FROM AUTHOR]

Artificial ground freezing (AGF) has emerged as a prominent treatment method due to its ability to mechanically strengthen the soil while reducing its permeability. However, its implementation has raised concerns about its impact, particularly with respect to frost heave and subsequent thaw-induced displacements. These soil movements can cause subsidence and pose a significant threat to the integrity of surface structures. Overburden pressure plays a crucial role in AGF and determines the amount of heave generated. This paper presents an analysis of the existing literature about soil freezing and thawing. The aim is to offer an understanding of these processes, specifically with regard to their application in AGF. This paper explains the behavior of soil during freezing, with particular emphasis on the influence of overburden pressure. It also investigates frozen soils' thawing and freeze–thaw (FT) cycles' long-term effects on soil properties. AGF offers improved soil strength and reduced water permeability, enhancing construction project stability. However, the interplay between the temperature, soil composition, and initial ground conditions during freezing is complex. This thermo-hydro-chemo-mechanical process strengthens the soil and reduces its permeability, but it can also induce frost heave due to water expansion and ice lens formation. Overburden pressure from the overlying soil limits ice lens growth. FT cycles significantly impact soil properties. In fine-grained soils, FT cycles can lead to over-consolidation, while rapid thawing can generate high pore pressures and compromise stability. Importantly, FT acts as a weathering mechanism, influencing soil properties at both the microscopic and macroscopic scales. These cycles can loosen over-consolidated soil, densify normally consolidated soil, and increase overall hydraulic conductivity due to structural changes. They can also weaken the soil's structure and deteriorate its mechanical performance. [ABSTRACT FROM AUTHOR]

As urbanization accelerates and surface space becomes increasingly scarce, the development and utilization of urban underground space have become more critical. The sand–fine mixture soils commonly found in river-adjacent and coastal areas pose significant challenges to the design and construction of underground structures due to their unique mechanical properties. In soil mechanics, the minimum and maximum void ratios are crucial indicators for assessing soil compressibility, permeability, and shear strength. This study employed the discrete element method (DEM) to simulate the minimum and maximum void ratios of sand–fine mixtures under various conditions by setting six fine contents and three mean diameter ratios. The results indicate that as the fine content increases, these void ratios exhibit a trend of initially decreasing and then increasing, which can be effectively modelled using a single-parameter quadratic function. Additionally, the initial shear modulus was closely related to the uniformity of contact distribution at the microscopic level within the specimens. This study also introduced a dimensionless parameter that simultaneously described changes in contact distribution and initial shear modulus. [ABSTRACT FROM AUTHOR]

Major flood propagation processes often cause instability and damage to the ancient waterfront city walls. To quantitatively reveal the impact of major floods on the stability of ancient city walls, this paper takes Lanxi's ancient city wall as a study object and constructs a numerical model to investigate the influence of the major flood process in 2017 on the wall stability and reveals the varying laws of its seepage, displacements, maximal shear stresses and safety factors with flood propagation time on the basis of flood level data, combining indoor experiments and field observations. The results show that flood level variations significantly affect the PWPs (pore water pressures) of the fillings behind the wall. During the flood period, the maximal horizontal and vertical displacements are mainly induced by soil extrusion and deformation, and the maximal shear stresses of the outer and inner wall also significantly increase. The changing rates of the wall's safety factors measurably exceed that of the flood level. The flood level variation range dramatically affects the safety factors when it changes near and above the wall foot. The minimum of the safety factors decreases with the increasing flood level falling rate when it drops near the wall foot at different rates. The ancient city wall usually does not experience serious instability under a single major flood. This study can provide a theoretical basis for the selection of reinforcement measures for flood control ancient city walls and the protection of ancient waterfront buildings. [ABSTRACT FROM AUTHOR]

Fault geometry is a key factor in controlling the mechanics of faulting. However, there is currently limited theoretical knowledge regarding the effect of non-planar fault geometry on earthquake mechanics. Here, we address this gap by introducing an expansion of the relation between fault traction and slip, up to second order, relative to the deviation from a planar fault geometry. This expansion enables the separation of the effects of non-planarities from those of planar faults. This expansion is realized in the boundary integral equation, assuming a small fault slope. It provides an interpretation for the effect of complex fault geometry on fault traction, for any fault geometry and any slip distribution. Hence, the results are also independent of the friction that applies on the fault. The findings confirm that fault geometry has a strong influence on in-plane faulting (mode II) by altering the normal traction on the fault and making it more resistant to slipping for any fault geometry. On the contrary, for out-of-plane faulting (mode III), fault geometry has a much smaller influence. Additionally, we analyse some singularities that arise for specific fault geometries often used in earthquake simulations and provide guidelines for their elimination. To conclude this study, we discuss the limits of the infinitesimal strain theory when non-planar faults are considered. [ABSTRACT FROM AUTHOR]

The Journal of Geotechnical and Geoenvironmental Engineering (JGGE) is a prestigious journal that recently celebrated its 150th volume. Published by ASCE and sponsored by ASCE's Geo-Institute (G-I), it stands out from other journals in the field. The journal has a strong international presence, with contributors and editorial board members from various countries. To mark this milestone, the journal made 10 important papers available for free and organized a special session at a conference. Over the years, the journal's name has changed to reflect the expanding focus on environmental considerations in geotechnical engineering. It has published groundbreaking research in areas such as soil mechanics, geotechnical earthquake engineering, geoenvironmental engineering, and ground engineering. The field of geotechnical engineering is adapting to address global challenges like climate change and the shift to low-carbon energy. The journal maintains its commitment to the peer review process and remains a valuable resource for researchers, practitioners, and students worldwide. [Extracted from the article]

Disposal of municipal solid waste is a significant environmental issue that has detrimental effects on both the environment and human life. The selection of landfill sites is critical and essential to implementing a comprehensive waste management strategy. This study optimizes the selection of landfill sites in Kuwait through the use of overlay analysis and Geographic Information System in conjunction with multi-criteria decision analysis. The study analysis takes into account human, physical economical, environmental, and governmental factors. Seven optimal locations are depicted on the resulting suitability map, each occupying 10 square kilometres or more and have the capacity to handle solid waste for at least one decade per site, considering the current reported waste generation rate. Furthermore, results of a preliminary geotechnical investigation encompassing field and laboratory tests conducted on soil samples collected at one of the proposed sites are presented. The characterization of the retrieved samples included major geotechnical parameters that are of concern in landfill design and siting studies. The results indicate that the soil at the proposed site exhibited low values of hydraulic conductivity, ranging between 3.50 X 10−07 and 8.96 X 10−08 cm/sec, confirming its suitability for siting landfills. There is an urgent need to develop and implement an integrated waste management system in Kuwait. By leveraging the findings of this study, policymakers and governmental authorities can optimize their decision-making procedures to ensure more effective site selection. This approach will significantly reduce contamination risks and enhance sustainability, leading to a more environmentally responsible waste management system in the country.

The use of a micropile group is an effective method for small and medium-sized slope management. However, there is limited research on the pile–soil interaction mechanism of micropile groups. Based on transparent soil and PIV technology, a test platform for the lateral load testing of slopes was constructed, and eight groups of transparent soil slope model experiments were performed. The changes in soil pressure and pile top displacement at the top of the piles during lateral loading were obtained. We scanned and photographed the slope, and obtained the deformation characteristics of the soil interior based on particle image velocimetry. A three-dimensional reconstruction program was developed to generate the displacement isosurface behind the pile. The impacts of various arrangement patterns and connecting beams on the deformation attributes and pile–soil interaction mechanism were explored, and the pile–soil interaction model of group piles was summarized. The results show that the front piles in a staggered arrangement bore more lateral thrust, and the distribution of soil pressure on each row of piles was more uniform. The connecting beams enhanced the overall stiffness of the pile group, reduced pile displacement, facilitated coordinated deformation of the pile group, and enhanced the anti-sliding effect of the pile–soil composite structure. [ABSTRACT FROM AUTHOR]

Clay–gravel mixture is an increasingly popular material used in geotechnical engineering for its engineering adaptability and easy accessibility. Among various granulometric factors, gravel content plays a critical role in the alteration of mixture microstructure. Its influence on mechanical behavior has been comprehensively investigated, yet the hydraulic models accounting for the paired impact of clay and gravel particles are seldomly discussed. In an effort to enhance the permeability prediction capability of this soil, a generalized binary model derived from a theoretical hydraulic conductivity expression is proposed, with the participation of two fundamental compound seepage models. High accuracy between test and calculation results indicates the reliability of this model, as well as its supremacy over conventional models. The parameter sensitivity analysis demonstrates that the proposed model, being of convincing parametric stability regardless of variant particle size distribution characteristics, has the potential to be applicable to a wide range of engineering-adapted CGMs. The predictive formula for cohesive fraction and the anomaly coefficient, as is integrated into the binary model, are explicitly discussed. Suitable for clay–gravel materials under a transitional soil state for engineering applications, this model provides a quantitative and reasonable evaluation of hydraulic conductivity with high practicality. The above findings might work as a perspective for the credible assessment of structure seepage safety behavior, as well as a quantitative evaluation method regarding the mixing quality of CGMs. [ABSTRACT FROM AUTHOR]

The soil‒water characteristic curve (SWCC) defines the relationship between the amount of water in soil and soil suction. The SWCC is commonly used to estimate the hydraulic conductivity function (HCF) and the shear strength function (SSF). Therefore, an accurate determination of the SWCC is crucial for implementing the principles of unsaturated soil mechanics. The SWCC is commonly determined from a limited number of experimental data because SWCC measurements are time-consuming and costly. As a result, the minimum number of required soil specimens is crucial for a SWCC test when considering the accuracy of the determined SWCC and the experimental expenses. In this study, both engineered from sand and kaolin mixtures and residual soils from Bukit Timah Formation in Singapore are selected to prepare soil specimens for SWCC measurements. The SWCCs obtained from the specimens with engineered soil are consistent, while those from specimens with residual soil are slightly scattered. This indicates that one specimen is sufficient to determine the SWCC for engineered soil samples, while a minimum of two specimens should be prepared for the determination of SWCC for residual soil samples from Bukit Timah Formation. [ABSTRACT FROM AUTHOR]

Swell-shrink characteristic soils exhibit a high susceptibility to cracking during the drying process, which poses a significant risk of various geological disasters. Among these, the occurrence of drying shrinkage acts as a prerequisite for the cracking phenomenon. Therefore, it is of utmost importance to comprehend the specific characteristics associated with the drying shrinkage mechanism. To investigate the drying shrinkage behavior of swell-shrink characteristic soils, a series of drying shrinkage experiments were conducted on long strip samples of red clay and expansive soil. Utilizing three-dimensional digital image correlation (DIC) technology, the surface displacement, strain, and anisotropic shrinkage rates of the soil samples during the drying process were obtained, and the size effect on the drying shrinkage of swell-shrink characteristic soil were analyzed. The research findings are as follows: The displacement development of the soil samples in the X and Y directions can be divided into two stages: a linear growth stage and a stable displacement stage. In the Z direction, the soil surface deformation can be divided into three stages: soil surface arching, vertical shrinkage, and shrinkage stabilization. The drying shrinkage of swell-shrink characteristic soil exhibits anisotropy, with the vertical shrinkage rate being the largest, followed by the longitudinal and then the transverse directions. Additionally, the soil sample shrinkage exhibits a size effect, whereby the shrinkage rates in all directions increase with increasing sample width and thickness. During the drying shrinkage process, the stress state on the soil surface evolves from initial tensile strain to subsequent compressive strain. The strain at different positions and times within the soil sample is not uniform, resulting in the non-uniformity and anisotropy of the sample shrinkage. This study provides important insights into the cracking mechanism of swell-shrink characteristic soils and serves as a valuable reference for related laboratory experiments, which will contribute to better prediction and control the geological hazards caused by the drying shrinkage of swell-shrink characteristic soils. [ABSTRACT FROM AUTHOR]

Grain size analysis is used to study grain size and distribution. It is a critical indicator in sedimentary simulation experiments (SSEs), which aids in understanding hydrodynamic conditions and identifying the features of sedimentary environments. Existing methods for grain size analysis based on images primarily focus on scenarios where grain edges are distinct or grain arrangements are regular. However, these methods are not suitable for images from SSEs. We proposed a deep learning model incorporating histogram layers for the analysis of SSE images with fuzzy grain edges and irregular arrangements. Firstly, ResNet18 was used to extract features from SSE images. These features were then input into the histogram layer to obtain local histogram features, which were concatenated to form comprehensive histogram features for the entire image. Finally, the histogram features were connected to a fully connected layer to estimate the grain size corresponding to the cumulative volume percentage. In addition, an applied workflow was developed. The results demonstrate that the proposed method achieved higher accuracy than the eight other models and was highly consistent with manual results in practice. The proposed method enhances the efficiency and accuracy of grain size analysis for images with irregular grain distribution and improves the quantification and automation of grain size analysis in SSEs. It can also be applied for grain size analysis in fields such as soil and geotechnical engineering. [ABSTRACT FROM AUTHOR]

This paper explores the influence of two thermal loading protocols on the evolutions of stress state and soil consolidation characteristics during subsequent mechanical loading. We employed a specially designed thermal consolidometer to conduct a series of drained heating tests with temperature gradient across a saturated kaolin specimen at different levels of vertical effective stress. The thermal consolidometer accommodated for (1) continuous measurements of excess pore water pressure and temperature at different locations within a specimen; and (2) establishment of a steady nonuniform soil temperature distribution, a condition that often exists in the field. Staged and cyclic thermal loading revealed the influences of vertical effective stress on total and nonrecoverable thermal strain. Continuous measurements of pore pressure and soil volume change traced the evolution of average vertical effective stress with void ratio. While the negative pore pressure measurements at the end of thermal consolidation of normally consolidated clay suggested a pseudo-overconsolidated behavior upon heating at low values of vertical effectives stress, such a tendency diminished with an increase in stress level. A gradual shift in normal consolidation line at ambient temperature suggested continuous hardening of a normally consolidated specimen when subjected to repeated thermal loading cycles in the past. [ABSTRACT FROM AUTHOR]

Soil mechanics traditionally have focused on studying pure clays and clean sands. However, natural soils and other geomaterials usually do not fall into these two classes. Most geomaterials are a complex matrix of fines and coarser particles, with distinct shapes and mineralogy interacting. This paper studied iron ore tailings over a broad range of pressures and stress histories to investigate the mechanical behavior of this nontextbook geomaterial. A thorough experimental program was conducted, and aspects of the stress–strain response, yielding, hardening, and critical state were evaluated. The state boundary surface of iron ore tailings also was investigated. The results demonstrated that the stress history of tailings affects the tailings' behavior only at elevated stress levels. The existence of particles with distinct mineralogy in the iron ore tailings (mainly iron oxide and quartz) could have induced different breakage patterns, with an evolving particle morphology being the dominant mechanism up to the pressures achieved. [ABSTRACT FROM AUTHOR]

Several biopolymer applications in geotechnical engineering have been adopted in recent years, notably dust control, soil strengthening, and erosion control. Although biopolymer soil treatment approaches can assure engineering efficiency while satisfying environmental protection standards, this technology requires more validation regarding site adaptability, durability, and economic feasibility. The influence of biopolymers on soil behavior is discussed within geotechnical engineering applications and practices, including soil consistency limits, strength and deformation parameters, hydraulic conductivity, soil-water properties, and erosion prevention. Laboratory studies were performed to confirm the behavior of the treated soil, including Atterberg limits, proctor, and direct shear tests utilizing two types of biopolymers: guar gum and xanthan gum. [ABSTRACT FROM AUTHOR]

Rolling dynamic compaction (RDC) has been found to be useful for compaction soils and is now widely used globally. Because RDC is not often used in soft soils with poor engineering properties, field monitoring was used to study the soft clay embankment responses under RDC conditions in this study. Analysis of the monitoring data revealed that the response of the soil occurred mainly in the first 20 passes. Field monitoring revealed a strong correlation between settlement, horizontal displacement, and pore water pressure. The depth of impact of RDC on the soft soil embankment was between 3 and 3.5 m. Although settlement prediction is an important issue for construction, there is a lack of prediction methods for RDC-induced soil settlement. In this study, we used three different machine learning algorithms: random forest regression (RFR), multilayer perceptron (MLP), and extreme gradient boosting (XGBoost) to predict the total settlement and uneven settlement induced by RDC on the soft soil embankment. The three prediction models were compared, and the predictive accuracy of these models was assessed. This study analyzes and summarizes the effect of RDC application on a soft clay embankment and explores the machine learning method used for settlement prediction based on monitoring data, which provides some methods and ideas for research on the application of RDC on soft soil foundations. [ABSTRACT FROM AUTHOR]

The construction of tunnels in conditions of dense urban development affects buildings, structures, and engineering communications located at the surface. In this work, through dispersion analysis, factors influencing the settlement of the earth's surface and buildings during tunneling were selected. Subsequently, a model based on statistically significant parameters that can predict deformations at the pre-design stage was created. This research was conducted using data from geotechnical monitoring obtained during the construction of underground structures, with information about the technological parameters of shield tunneling in the construction of the single-track lines of the Moscow Metro using TBM with face-support pressure and engineering–geological conditions. In the obtained model, there is a clear dependency between the additional displacement of the monitoring object located above the projected tunnel and the average face-support pressure causing the mentioned deformations. The response is also affected by the soil deformation model at the tunnel face, the depth of the tunnel, and the soil excavation for the installation of one ring. [ABSTRACT FROM AUTHOR]

The emerging upward shield method (USM) for constructing vertical shafts has been used in various projects, including the Midosuji utility tunnel in Japan. A scaled-down model testing system, featuring a geometric similarity ratio of 1:30, was developed specifically for studying the USM. This system incorporates sand inflow control, propulsion control, data acquisition, and water level control. It facilitates detailed observation and recording of parameters such as vertical displacement of surface soil layers, support force at the excavation face, and earth pressure within the model box. Consequently, it enables investigation into the excavation face instability process, modes, and the formation and evolution of the soil arch zone above the excavation face during upward shield tunneling. Additionally, through the application of particle image velocimetry (PIV) technology and GeoPIV-RG software v1.1, quantitative analysis of soil displacement fields during excavation face instability is conducted, capturing microscopic displacements and deformations of soil planes. This approach more accurately elucidates the accuracy of understanding the dynamic response of soil. Pre-test research using the model testing system explores the variation patterns of excavation face load displacement, vertical earth pressure within the failure zone, surface displacement, and internal soil displacement during the instability process. Analysis reveals that excavation face load variation typically progresses through three stages: rapid growth, slow growth, and descent. Moreover, vertical earth pressure shifts upward in tandem with excavation face displacement, while overall surface displacement initially shows slight settlement followed by accelerated uplift. [ABSTRACT FROM AUTHOR]

Using the Vertical Shaft Sinking Machine (VSM) for shaft construction is an emerging modern technology, which is also currently one of the most advanced techniques in the field of shaft sinking. Current research on VSM technology primarily focuses on mechanical and technical issues, neglecting the impact of the construction on the surrounding soil and the structure itself. This oversight leaves structural design lacking a reliable foundation. Additionally, there is insufficient information on the role of reinforcement design during construction in soft soils. These engineering challenges have hindered the widespread implementation of this new technology. Therefore, a series of numerical models were used to analyse the mechanical behaviour of shaft and soil during or after the sinking process, with the aim of addressing these gaps by investigating the influence of shafts constructed using VSM technology, and providing a scientific basis for reinforcement design in soft soil. The case study shows that increasing the soil-cement strength does not have a significant effect on the overall deformation of the soil surrounding the shaft, but leads to a notable reduction in the plastic zone volume, subsequently enhancing the overall stability of the neighbouring soil. The ring bottom beam design effectively reduces convergence deformation by about 50%, while also improving the horizontal internal force distribution near the cutting edge. However, this approach significantly escalates local vertical bending moments, necessitating thorough consideration in the design stage. [ABSTRACT FROM AUTHOR]

Three soft rock facies of the Middle Globigerina Limestone (MGL) from Malta, of mineralogical composition and index properties similar to some medium-high density Chalk facies, are disaggregated through prolonged agitation in water to create reconstituted samples. The significant activity of their clay-sized calcite grains can impart a medium-high plasticity. Scanning electron microscopy analyses of natural and reconstituted samples show the natural bonding as interlock, possibly induced by cohesive clay-sized calcite grains during the sediment compaction. Micro-analyses and compression test data also show that local calcite crystal overgrowth under burial has reduced further the soft rock porosity, making it lower than that of the reconstituted material one-dimensionally compressed to the geological preconsolidation pressure. Nonetheless, the low stress sensitivity of natural MGL suggests that this interlock bonding does not strengthen much the material with respect to the highly compressed reconstituted soil. The natural MGL is of very low permeability, which reduces further with compression. Concurrently, the soft rock creep coefficient increases, reaching values far above those typical for clays. The microstructural features and the mechanical properties of the different MGL facies are shown to be sensitive to clay mineral content. [ABSTRACT FROM AUTHOR]

This research develops an elastoplastic damage constitutive model incorporating the strain softening response of common engineering soil materials in southeastern Xizang to evaluate and optimize reinforcement solutions for highway-traversing landslide accumulations. Grounded in deterioration mechanics theory, the model characterizes the progressive strength loss and failure evolution of the soils. Verified and calibrated, it is numerically implemented in FLAC3D to simulate the stability conditions of a landslide affecting planned highway infrastructure in southeastern Xizang. Safety factors of 1.25, 1.07, and 1.02 under normal operation, rainfall, and seismic excitation loads, respectively, reveal the inadequacy of intrinsic stability. Consequently, dynamic compaction and chemical grouting techniques are assessed via simulation. An optimal strategy, entailing 6-m-deep densification at the highway location with 10% silica fume enhancement of 66.3% of the landslide area and 50.8% of the soil-bedrock interface, results in safety factors of 1.70, 1.49, and 1.23 for the three scenarios. The improved area is minimized to streamline construction practicality and economics while preserving geotechnical integrity. The integrated modeling outcomes demonstrate the model's capability in capturing localized incremental damage and the efficacy of numerical simulation for stability diagnosis and targeted remediation of intricate landslides. Advancements in constitutive relations development are vital for further innovation in geohazard evaluation and infrastructure safety assurance. [ABSTRACT FROM AUTHOR]