In cold regions, the strength and deformation characteristics of frozen soil change over time, displaying different mechanical properties than those of conventional soils. This often results in issues such as ground settlement and deformation. To analyze the rheological characteristics of frozen soil in cold regions, this study conducted triaxial creep tests under various creep deviatoric stresses and established a corresponding Discrete Element Method (DEM) model to examine the micromechanical properties during the creep process of frozen clay. Additionally, the Burgers creep constitutive model was used to theoretically validate the creep deformation test curves. The research findings indicated that frozen clay primarily exhibited attenuated creep behavior. Under low confining pressure and relatively high creep deviatoric stress, non-attenuated creep was more likely to occur. The theoretical model demonstrated good fitting performance, indicating that the Burgers model could effectively describe and predict the creep deformation characteristics of frozen clay. Through discrete element numerical simulations, it was observed that with the increase in axial displacement, particle displacement mainly occurs at both ends of the specimen. Additionally, with the increase in creep deviatoric stress, the specimen exhibits different deformation characteristics, transitioning from volumetric contraction to expansion. At the same time, the vertical contact force chains gradually increase, the trend of particle sliding becomes more pronounced, and internal damage in the specimen progresses from the ends toward the middle.

In this paper, through extensive on-site research of the plain concrete composite foundation for the Jiuma Expressway, the study conducted proportional scaling tests. This study focused on the temperature, moisture, pile-soil stress, and deformation of this foundation under freeze-thaw conditions. The findings indicate that the temperature of the plain concrete pile composite foundation fluctuates sinusoidally with atmospheric temperature changes. As the depth increases, both temperature and lag time increase, while the fluctuation range decreases. Furthermore, the effect of atmospheric temperature on the shoulder and slope foot is more significant than on the interior of the road. During the freeze-thaw cycle, the water content and pore-water pressure in the foundation fluctuate periodically. The pile-soil stress fluctuates periodically with the freeze-thaw cycle, with the shoulder position exhibiting the most significant changes. Finally, the road displays pronounced freeze-thaw deformations at the side ditch and slope toe. This study provides a valuable basis for the construction of highway projects in cold regions.

In the loess tableland, gully slope instability induces severe soil erosion and land degradation, yet the synergistic effects of dominant vegetation under varying restoration modes combined with dynamic rainfall regimes and topographic variations on gully slope stabilization mechanisms remain inadequately quantified. Therefore, the dominant vegetation species under natural (NR) and artificial restoration (AR) was chosen as the object. Through field sampling, root-soil complex mechanical experiments, and numerical simulations, the protection effect of dominant vegetation under different restoration modes combination with rainfall and topographic variations was investigated. The result revealed significant differences in basic soil physical properties, root morphological characteristics, root and root-soil complex mechanical properties among five dominant vegetated plots under the different restoration modes (P < 0.05). The soil properties in the Scop plot under AR were slightly better than those in the other plots. The roots in the Spp plot developed better under NR. The shear strength of Lespedeza bicolor Turcz. was the highest under NR. The tensile strength of Digitaria sanguinalis (L.) Scop. was greatest under AR. The tensile force and tensile strength of single roots exhibited a significant positive linear correlation and a significant negative exponential correlation, with root diameter, respectively (P < 0.01). For the unstable gully slopes (F-s < 1.0), maximum displacement occurred at the slope foot, where tensile shear failure dominated, while the interior experienced compressive yielding. The grey relational analysis identified rainfall intensity as the primary destabilizing factor, followed by dominant vegetation species, slope height, and slope gradient. Notably, when rainfall intensity reaches or exceeds 0.06 m/h, or when slope height exceeds 20 m combined with long-duration rainfall, the regulatory impacts of dominant vegetation under different restoration modes on the gully slope stability are substantially diminished and become negligible. This study provides a theoretical basis for gully slope protection and ecological environmental construction in loess tableland.

The displacements between segment rings are highly likely to occur in concealed creep fault areas. The dislocation of ring joint easily leads to the crushing of concrete around the bolt hole, which will become a potential safety hazard during tunnel service. For this problem, a composite Tenon was designed to improve the interaction at ring joint. It is necessary to carry out theoretical research to reveal the mechanical property of the ring joint. In this paper, a constitutive model of the Tenon was proposed based on specimen tests and numerical models. And the mechanical characteristics of the ring joint were investigated through prototype experiment and numerical simulation. The research results show that the composite Tenon is a flexible structure that can avoid the hard extrusion between the Tenon and the segments. The Tenon also has obvious protection effect on bolt and concrete around the handhole, which reserves more bearing space for the ring joint. These advantages are more conducive to dealing with potential risks such as earthquake, cyclic train loads, tunnel convergence deformation and uneven soil settlement during operation. The paper provides a theoretical basis for the application and promotion of the composite Tenon structure in the tunnel engineering.

This study investigates the mechanical, thermal, and wears characteristics of eco-friendly composite materials (designated as N1 to N5) with varying ratios of silicon nitride (biogenic Si3N4) and biochar along with jute and kenaf microfiber. The primary aim of this research study was to investigate the suitability of low cost biomass derived functional ceramic fillers in composite material instead of high cost industrial ceramics. Both the bio carbon and biogenic Si(3)N(4 )were synthesized from waste sorghum husk ash via pyrolysis and thermo-chemical method. Further the composites are prepared via mixed casting process and post cured at 100 degrees C for 5 h. According to results, the mechanical properties show a consistent improvement, attributed to the contributions of biogenic Si3N4. Moreover, the specific wear rate decreases progressively, with a larger biogenic Si(3)N(4 )and bio carbon filler %. The presence of biochar acts as solid lubricant and offered balanced friction coefficient. The composite N4 attained maximum mechanical properties including tensile (110 MPa), flexural (173 MPa), impact (6.1 J), hardness (82 shore-D), compressive (138 MPa) and lap shear strength (16 MPa). On contrary, the composite N5 attained least thermal conductivity of 0.235 W/mK, Sp. Wear rate of 0.00545 with COF of 0.26. Similarly, the scanning electron microscope (SEM) analysis revealed highly adhered nature of fillers with matrix, indicating their cohesive nature indicating the strong interfacial adhesion between the fillers and the matrix, attributed to the presence of biochar, which enhances mechanical interlocking and provides functional groups that promote chemical bonding with the polymer matrix, leading to improved load transfer efficiency and overall composite performance. Moreover, thermal conductivity values exhibit a marginal decline with the presence of biogenic Si(3)N(4)and biochar. Overall, the study demonstrated that biomass-derived functional fillers are capable candidates for providing the required toughness and abrasion-free surfaces, as evidenced by the increased impact strength, improved wear resistance, and enhanced durability observed in treated specimens compared to the control samples.This approach offers both economic and environmental benefits by reducing human exposure to hazardous pollutants through the utilization of biomass-derived materials, which help divert waste from landfills, lower air pollution caused by burning conventional plastics, and minimize soil contamination from non-biodegradable waste. In addition, the developed natural fiber-reinforced composites exhibited competitive mechanical performance compared to conventional industrial ceramic-reinforced composites, demonstrating comparable strength, enhanced toughness, and improved damping properties while offering the advantages of lower density, biodegradability, and cost-effectiveness. These findings highlight the potential of biomass-derived fillers as sustainable alternatives in structural applications.

Gravelly soils, characterized by a distinctive combination of coarse gravel aggregates and fine soil matrix, are widely distributed and play a crucial role in geotechnical engineering. This study investigates the mechanical behavior of gravelly soil subjected to simulated freeze-thaw (F-T) cycles using triaxial compressive strength tests. The long-term deviatoric stress response of specimens with varying gravel content and initial water content was analyzed under three distinct effective confining pressures (100, 200, and 300 kPa) across different F-T cycles. The results indicate that compressive strength is significantly influenced by gravel content, initial water content, and confining pressure. Notably, the rate of increase in deviatoric stress does not exhibit a proportional rise under confining pressures of 200 kPa and 300 kPa after 40 F-T cycles. However, a direct correlation is observed between deviatoric stress and increasing confining pressure (100, 200, and 300 kPa) over 2-, 4-, and 6-day intervals, this effect is more pronounced at higher confining pressures. The deviatoric stress peaks at different strain thresholds depending on the applied confining pressure; furthermore, no evident strain-softening behavior is observed across the tested conditions. These findings suggests that higher confining pressure inhibits particle displacement and interlocking failure, thereby reducing both the void ratio and axial strain within the soil matrix. Overall, these insights enhance our understanding of the complex interactions among gravel content, water content, confining pressure, and freeze-thaw effects, contributing to the understanding of the compressive strength evolution in gravelly soils under cyclic environmental loading.

The reinforcement and repair materials for earthen sites have high requirements for strength, resistance to deterioration, and aesthetic coordination. In this study, the enzyme-induced carbonate precipitation (EICP) and the microbially induced carbonate precipitation (MICP) techniques were used to reinforce the earthen site soil. The applicability of EICP and MICP for stabilizing earthen sites soil was investigated through static contact angle tests, disintegration tests and colorimetry tests. In addition, the improvement of mechanical properties of biotreated earthen sites soil was examined by unconfined compression strength tests. The tests results show that MICP and EICP techniques could improve the mechanical characteristics and water-stability properties of the earthen sites soil. With the increase in cementing solution concentration, the effectiveness of EICP was enhanced, while the water-stability and hydrophobicity of MICP-treated soils increased first and then decreased due to the influences of organic matter and soluble salts. EICP and MICP techniques showed different performance in reinforcing effects on calcium carbonate content, shear wave velocity, unconfined compressive peak strength, total disintegration time, and static contact angle. This study is expected to contribute valuable insights to the conservation of earthen heritage site using bio-based methods.

Many engineering activities are conducted on marine soft soil foundations, with various types of soft soil influencing these projects differently. Studying the engineering characteristics and deformation mechanism of marine soft soil is crucial for the design and construction of marine structures. To reveal the dynamic mechanical characteristics of marine soft soil under wave loading, a set of soil samples under different confining pressure conditions were tested via a dynamic triaxial apparatus. Furthermore, a constitutive model was developed to predict the dynamic strength of marine soft soil subjected to wave loading. The experimental results demonstrate that the dynamic stress-strain behaviour of marine soft soil progresses through three stages: compaction, deformation, and failure. The dynamic strain-time history curve of the soil exhibited a cyclic trend characterized by a superposition of monotonic changes, which was attributed to the simultaneous occurrence of plastic deformation and cyclic deformation. The strain rebound gradually disappears with increasing number of loading cycles; the strain accumulation mainly occurs as compressive strain during the postvibration period. Within each stage, the dynamic shear modulus decreases with increasing shear strain, showing consistent curve characteristics across different dynamic stress amplitudes. During long-term cyclic loading, the damping ratio initially decreases and then stabilizes, with a negligible influence from the confining pressure. The Martin-Davidenkov constitutive model effectively characterizes the correlation between the dynamic shear modulus and shear strain, with fitting curves closely matching the measured data.

In recent years, biopolymers have been widely used in soil, but few concentration on the application of biopolymers in the organic soil. In this work, the potential using locust bean gum for improving the physical characteristics of the organic soil has been fully evaluated, while the Atterberg limit test, unconfined compressive strength test, and unconsolidated undrained shear test were conducted. In addition, the mineral composition and micro-mechanisms have been analyzed by X-ray diffraction tests, Fourier transform infrared spectra tests, and scanning electron microscopy tests. And we found that locust bean gum could increase the liquid limit and plastic limit of the organic soil, and enchance the compressive strength and shear strength. The increase in soil cohesion with locust bean gum content was more pronounced than the increase in internal friction angle. And as the curing time progresses, locust bean gum gradually transformed from a hydrogel state to a high tensile strength biofilm or flocculent gel matrix, which enhanced the bonding force between soil particles, thus increasing the strength of the specimens, which can be validated by the scanning electron microscopy observations, in which the porosity of soil was significantly reduced. We believed that this work could provide an ecological, economical and practical insight dealing with the engineering project constructions in the organic soil area.

Incorporating sustainable stabilizers into the geo-ecosystem is an effective approach to improving the mechanical properties of the soil while addressing ecological issues. The main objective and novelty of this study are to assess the combined use of palm fiber and guar gum in soil stabilization, estimate their behavior in practices, outline their obstacles and potential for soil improvement, and consider their ecological effects. For this purpose, four different dosages of guar gum (0.5, 1, 1.5, and 2%) and three ratios of palm fiber (0.2, 0.4, and 0.6%) in lengths (5, 10, and 15 mm) were considered. Laboratory tests conducted for this purpose include compaction, compressive, shear, and tensile strength, California bearing ratio (CBR), and microstructure analysis. Initially, the optimal dosage of guar gum was determined through the unconfined compressive test. Subsequently, the impact of optimal guar gum and palm strands on the mechanical characteristics of treated soil was examined. The results revealed that compressive and shear strengths of stabilized and reinforced soil improved by 200% and 71%, respectively, compared to the control samples. Also, increasing the palm dosage improved the failure strain by up to 11.4%, cohesion enhancement by up to 96 kPa, and soil brittleness reduction by 13.5%. The tensile and CBR test results demonstrated that incorporating fiber into the soil increased its tensile strength and CBR by 32.5 kPa and 31.16, respectively. A microstructure study revealed that adding guar gum to the fiber composite improved the interlocking between clay particles and fibers by generating a hydrogel.