Foundation soil treatment is a common method used to enhance soil strength in civil engineering, particularly in cold regions where ambient temperatures significantly affect soil mechanical properties. This study investigates the utilization of cement and municipal solid waste incinerator bottom ash (MSWIBA) for stabilizing silty clay under low-temperature curing conditions. Some experiments were performed to investigate the mechanical properties of cement-stabilized silty clay, varying the dosage of bottom ash (BA) and different curing temperatures. The influences of BA dosage, curing temperature and age on the shear and compressive strengths of soils were tested and analyzed. Results demonstrated that the shear strength was influenced by the comprehensive interactions among BA particles, soil particles, and ice crystals. Regardless of curing temperature and age, the shear strength of soil specimen firstly increased and then declined with BA dosage raised, with an optimal BA content range from 20 % to 30 %. Specifically, the 28-d shear strength enhancements of 2.46 %, 15.52 %, 20.20 %, and 11.33 % were observed with each successive 10 % BA addition for soil samples at 10 degrees C curing condition. Curing temperature significantly influenced shear strength, with higher temperatures promoting greater strength due to increased hydration reaction rates. Besides, the cohesion and internal friction angle of samples increased with BA dosage. Furthermore, the axial stress-strain curves illustrated a three-stage process, i.e., initial pore compression, plastic deformation, and decay stages. The compressive strength raised with both the BA dosage and curing age, with positive curing temperatures yielding higher strengths compared to sub-zero temperatures. This study elucidates the complicated mechanical behavior of BA-cement stabilizing silty clay, providing valuable insights into their performance under different curing conditions, and offering an innovative approach for foundation engineering applications in cold regions.

The interface between geotextile and geomaterials plays a crucial role in the performance of various geotechnical structures. Soil-geotextile interfaces often suffer reduced performance under environmental stressors such as rainfall and cyclic loading, limiting the reliability of geotechnical structures. This study examines the influence of gravel content (Gc), compaction degree (Cd), and rainfall duration (Rd) on the mobilized shear strength at the silty clay-gravel mixture (SCGM)- geotextile interface through a comprehensive series of direct shear tests under both static and cyclic loadings. A novel approach using Polyurethane Foam Adhesive (PFA) injection is introduced to enhance the interface behavior. The results reveal that increasing Gc from 0 % to 70 % leads to a 35-70 % improvement in mobilized shear strength and friction angle, while cohesion decreases by 15 %-60 %, depending on Cd. A higher Cd further boosts shear strength by 6 %- 70 %, influenced by Gc and normal stress levels. Under cyclic loading, increasing displacement amplitude reduces shear stiffness (K), while having minimal impact on the damping ratio (D); K and D appear unaffected by the number of cycles in non-injected samples. Rainfall reduces mobilized shear strength by 8 %-25 %, depending on the normal stress, with a 47 % drop in friction angle and a 24 % increase in cohesion after 120 minutes of rainfall exposure. In contrast, PFA-injected samples exhibit a marked increase in mobilized shear strength under both dry and wet conditions, primarily attributed to enhanced cohesion. Notably, PFA treatment proves particularly effective in maintaining higher shear strength and stiffness in rainfall-affected interfaces, demonstrating its potential in improving geotextile-soil interaction under challenging environmental conditions.

The large amount of slag generated during the construction of earth pressure balance shield (EPBS) not only incurs significant disposal costs, but also exacerbates environmental pollution. To improve the utilization of the shield slag, silty clay with additive is proposed as a slag conditioner instead of bentonite. Firstly, various macroscopic properties of the bentonite and silty clay slurries are tested. Subsequently, the relationships between the macroscopic properties of the silty clay slurries containing additives and the modification mechanism are evaluated at microscopic, mesoscopic, and macroscopic scales by using infrared spectroscopy (IR), scanning electron microscope (SEM), and Zeta potential tests, respectively. Based on these tests, reasons for variations in modification effects of different slurries are identified. The results show that addition of 3 % sodium carbonate to the silty clay can effectively improve the rheological properties of the slurry. The modification mechanism of sodium carbonate involves the formation of hydrogen bonds between water molecules and inner surface hydroxyl groups within the lattice layer of kaolinite. This process significantly enhances the rheological properties of the silty clay slurry. Furthermore, sodium carbonate alters the contact relationships between the silty clay particles, which increases viscosity and reduces permeability of the slurry. Finally, sodium carbonate increases thickness of the electrical double layer of the silty clay particles. This allows the particles to bind more water molecules, therefore improving slurry-making capacity of the silty clay. This paper presents an innovative multiscale analysis of the modification process of silty clay. The substitution of recycled silty clay for bentonite as a slag conditioner not only substantially reduces the cost of purchasing materials, but also considerably decreases the expenses associated with transportation and disposal of the soil discharged by EPBS.

This study investigates the mechanical performance and deformation characteristics of reinforced retaining walls constructed with stabilized silty clay and geogrid reinforcement. Laboratory tests evaluated the physical and mechanical properties of native silty clay, identifying its high water content and poor gradation as primary challenges for engineering applications. A stabilization method incorporating 2 % soil stabilizing liquid, 10 % densifying powder, and 4 % Portland cement was optimized to enhance clay compaction, shear strength, and compressive strength. Model experiments were conducted under varying wall configurations, including natural slopes, stabilized retaining walls, and reinforced stabilized walls with different slope ratios. Results show that the combination of stabilization and reinforcement significantly improved load-bearing capacity, minimized vertical settlement, restricted horizontal displacement, and reduced lateral earth pressure. Comparative analysis of slope ratios revealed that gentler slopes enhanced deformation resistance and reduced geogrid strain. These findings offer practical insights and theoretical support for designing efficient retaining wall systems using stabilized silty clay.

Unlike uniform soils, soft clays with sand interlayers in coastal soft clays, can affect their mechanical properties, potentially impacting underground-construction safety and stability. Consolidated undrained cyclic triaxial tests were conducted to study the dynamic properties and deformation behavior of clay, focusing on how the thickness ratio between the sand and clay layers and the cyclic-stress ratio influence the pore pressure, axial strain, shear-modulus ratio, and normalized damping ratio. The results indicate that higher thickness ratios and cyclic-stress ratios lead to a faster decay of the shear-modulus ratio, quicker increases in pore pressure, faster strain accumulation, and fewer cycles to failure. The normalized damping ratio has three different forms: decreasing, decreasing then increasing, and increasing. However, at a cyclic-stress ratio of 0.2 and thickness ratio of 0.25, the samples exhibit better dynamic characteristics. Soft clay with sand layers exhibits characteristics in line with the stability theory. At low thickness and cyclic-stress ratios, purely elastic and elastically stable phases are observed. As the thickness and cyclic-stress ratios increase, it transitions to plastic stability and incremental failure.

This study explores a novel stabilization technique combining Persian gum (PG), an eco-friendly biopolymer, and glass fiber (GF) to enhance the strength and durability of fine-grained soils under freeze-thaw (F-T) cycles. Specimens were prepared at maximum dry density (MDD) with varying PG and GF contents, cured for 0, 7, or 14 days, and subjected to 0, 5, 7, or 10 F-T cycles. Tests included Standard Proctor compaction, Scanning Electron Microscopy (SEM), Unconfined Compressive Strength (UCS), and Direct Shear (DS). Results demonstrated that GF significantly improved durability, ductility, and strength by enhancing interparticle interaction and friction angle. The results indicated that at an optimum GF content of 1%, UCS and E-5(0) increased by up to 35%. Also, after 10 F-T cycles, UCS decreased by 46% for untreated soil and 36% for treated soil. PG enhanced cohesion through interparticle bonding, which was curing-time-dependent. Specimens with 2.5% PG (optimum content) showed a 133% UCS increase after 14 days of curing but a 9% reduction after 5 F-T cycles, with 70% of total UCS loss occurring in the first 5 cycles. The tests indicated that formation of large and stable soil-PG-GF matrix with improved rigidity, strength, and F-T resistance. The results demonstrated that the suggested soil stabilization method, which utilizes low-cost, eco-friendly materials, was effective.

Frozen soil is a common foundation material in cold region engineering. Therefore, the control and prediction of cumulative plastic strain for frozen soil materials are essential for the construction and long-term stability of actual foundation engineering under complex dynamic loadings. To investigate the influence of complex cyclic stress paths on frozen soil, a series of complex cyclic stress paths were conducted using the frozen hollow cylinder apparatus (FHCA-300).These cyclic stress paths included the triaxial cyclic stress path (TCSP), directional cyclic stress path (DCSP), circular-shaped cyclic stress path (CCSP), elliptical-shaped cyclic stress path (ECSP), and heart-shaped cyclic stress path (HCSP).The results indicated that the cumulative plastic strain under the five cyclic stress paths at three temperatures (-1.5,-6,and-15 degrees C) can be ranked as follows: DCSP>ECSP>HCSP>CCSP>TCSP. The cyclic stress paths are quantified based on the combined effects of the maximum shear stress (q(max)) and the principal stress axis angle (a). A developed model predicting cumulative plastic strain, considering complex cyclic stress paths, is introduced and demonstrates excellent predictive performance. The study's findings can offer insights into foundation engineering's deformation characteristics and settlement predictions under diverse complex dynamic loadings

Soil-pile interaction damping plays a crucial role in reducing wind turbine loads and fatigue damage in monopile foundations, thus aiding in the optimized design of offshore wind structures and lowering construction and installation costs. Investigating the damping properties at the element level is essential for studying monopole-soil damping. Given the widespread distribution of silty clay in China's seas, it is vital to conduct targeted studies on its damping characteristics. The damping ratio across the entire strain range is measured using a combination of resonant column and cyclic simple shear tests, with the results compared to predictions from widely used empirical models. The results indicate that the damping ratio-strain curve for silty clay remains S-shaped, with similar properties observed between overconsolidated and normally consolidated silty clay. While empirical models accurately predict the damping ratio at low strain levels, they tend to overestimate it at medium-to-high strain levels. This discrepancy should be considered when using empirical models in the absence of experimental data for engineering applications. The results in this study are significant for offshore wind earthquake engineering and structural optimization.

In soft soil environments, deep foundation pit excavation often leads to significant surface settlement, lateral displacement of support structures, and uneven settlement of surrounding buildings due to the complex geotechnical conditions and the inherent characteristics of soft soil, such as high compressibility and low shear strength. This study systematically analyzes 23 deep foundation pit excavation cases from Ningbo city, located in a silty clay region, to examine the deformation behavior during excavation. The research focuses on the impact of key factors such as excavation depth, pit dimensions, support structure parameters, and soil characteristics on the deformation of diaphragm walls. The results show that the maximum lateral displacement of diaphragm walls ranges from 0.09 to 0.84% of the excavation depth, with an average value of 0.36%. Deeper excavations lead to greater lateral deformation due to increased soil pressure and pore water pressure, with the maximum displacement typically occurring at 1.0-1.3 times the excavation depth. Soft soil thickness significantly amplifies wall deformation, with the displacement ratio increasing linearly with the ratio of soft soil thickness to wall depth. Increased wall stiffness, embedment depth, and support system stiffness effectively reduce lateral displacement. These findings provide a quantitative basis for optimizing diaphragm wall design and support systems to mitigate deformation risks, offering valuable guidance for deep foundation pits in similar soft soil environments.

To investigate the mechanical characteristics of frozen silty clay under complex stress paths, using the true triaxial instrument for permafrost, tests were carried out under triaxial compressive and plane strain stress states using the true triaxial instrument for permafrost to analyze deformation characteristics and strength evolution law under different stress paths and minor principal stresses (sigma(3)) and establish strength criterion under plane strain conditions. PFC3D numerical simulation results were compared to test results and meso-crack evolution law was discussed. The results showed that stress-strain curves were characterized by strain hardening. Destructive strength showed a gradual increase with the increase of sigma(3) and the values obtained from plane strain tests were higher than those of triaxial compression tests. Volume strains basically showed shear shrinkage characteristics and all sigma(3) directions were expansion deformation. Strength at damage under plane strain state was approximated based on generalized Mises and Lade-Duncan plane strain strength criterion using generalized plane strain strength criterion. Stress-strain curves obtained from numerical simulation tests in PFC3D basically agreed well with those obtained from indoor test results. The number of tensile and shear cracks in the developed numerical model under various stress paths were increased with generalized shear strain.