Mechanical properties of undisturbed root–soil composites were investigated through direct shear tests under different cementation concentrations by microbially induced carbonate precipitation (MICP). The results show that MICP has a significant strengthening effect on the undisturbed root–soil composite, and the maximum shear strength increases by about 160% after grouting. The shear strength of root–soil composites increases with the increase in calcium chloride concentration, and the shear strength increases the most when the concentration is 0.75M. Calcium carbonate formed by MICP treatment has cementitious properties, which increases the cohesion and internal friction angle of the root–soil composite by about 400% and 120%, respectively. The results show that it is feasible to solidify slope and control soil erosion together with microbial and vegetation roots. The research results can serve as a scientific basis and reference for the application of MICP technology in vegetation slope protection engineering.

Extensive bedding planes have a great influence on the mechanical properties of coal. In order to study the mechanism of the effects of bedding angles on the mechanical properties and failure characteristics of coal in the Shanxi Baode coal mine, uniaxial and triaxial compression tests and numerical simulations were conducted. The strength deterioration and microstructural changes in the samples were then analyzed with discrete element method (DEM) numerical simulation. The experimental results reveal that the power function strength criterion has good applicability to the strength characteristics of this coal. It was also found that the bedding angles have a great influence on the mechanical properties of coal. The properties of peak strength at different bedding angles roughly showed a U-shaped changing trend. The maximum strength occurred at a bedding angle of 0°, whereas the minimum strength occurred at a bedding angle of 60°. The numerical simulation and test results prove that the forms of failure of different bedding coal samples are complicated and are mainly represented by tensile and shear failures.

Rock engineering is highly susceptible to cyclic loads resulting from shale gas exploitation; it is very important to study the failure mechanism of underground rock mass under cyclic load. To investigate the energy dissipation and damage evolution characteristics of shale under triaxial cyclic loading and unloading conditions, a series of triaxial incrementally cyclic loading and unloading tests under different confining pressures (10 MPa, 15 MPa, 20 MPa, and 30 MPa) were carried out. The variation of plastic strain of shale under four confining pressures was analyzed, and the evolution characteristics of dissipated energy and energy dissipation ratio were discussed. The results show that: the peak strength and peak strain of shale increase with the increase in confining pressures. Meanwhile, the plastic strain of rock under cyclic loading increases rapidly first, then develops steadily, and finally increases sharply with the increase in axial strain. The energy dissipation ratio-strain curve presents a spoon-shaped evolution feature, and can be divided into three stages: a linear decline stage, a steady development stage, and a rapid increase stage, respectively. However, the trend of elastic modulus of shale was opposite to that of the energy dissipation ratio. Accordingly, the energy dissipation ratio can be regarded as the damage factor to describe the degradation of shale. Based on the evolution of dissipated energy, a theoretical equation of shale stress-strain evolution was established. By substituting the test data into the formula, it is found that the calculated results are basically consistent with the test data, and the peak strains and peak stress calculated by the equation are in good agreement with the test data. The findings could provide important theoretical support for the energy dissipation and damage evolution analysis in the failure process of shale under cyclic stress conditions.

Microbial induced carbonate precipitation (MICP) in coordination with vegetation protection is a novel technology in the field of slope reinforcement. Urea in MICP can promote vegetation growth and change the root content in the soil. However, existing studies often ignore the influence of MICP on root growth, while root content has a significant impact on the ability of vegetation to cement soil and protect slopes. In this paper, through the laboratory direct shear test, the strength variation characteristics of root‐soil composites with different root contents before and after reinforcement were analyzed, and the influence of root content changes on the strength of root‐soil composites in the MICP collaborative slope protection project was studied. The results showed that: (1) the strength of the root‐soil composite was improved significantly after MICP treatment. When the root content was 1.5%, the maximum strength peak value was increased by 32.6%, and the cohesive force was increased by 49.2%. (2) MICP reaction has no effect on the root content of the peak intensity, indicating that MICP has no negative effect on vegetation growth and can be combined with vegetation protection. The results show that MICP synergistic slope protection has strong engineering application value.

Presented in this paper is a study on the lateral unloading creep tests under different excess pore water pressures. The marine sedimentary soft soil in Shenzhen, China, was selected in this study. The results show that the excess pore water pressure plays a significant role in enhancing the unloading creep of soft soil. Higher excess pore water pressure brings more obvious creep deformation of soft soil and lower ultimate failure load. Meanwhile, the viscoelastic and the viscoplastic modulus of soft soil were found to exponentially decline with creep time. A modified merchant model and a combined model of the modified merchant model and plastic elements are used to simulate the viscoelastic and the viscoplastic deformation, respectively. Therefore, a lateral unloading creep model of soft soil is developed based on the modified merchant model. The accuracy and applicability of this model were verified through identifying the parameters in the model. Research results are of particular significance to the numerical simulation of underground space excavation in soft soil areas which considers the effects of excess pore water pressure.

Given the constraints of transportation conditions and cost, using traditional gravel soil with favorable properties for backfilling is often impractical in remote desert highway construction. Consequently, aeolian sand, which is abundant in these regions, provides a promising alternative for roadbed backfill. This study investigates the feasibility of substituting gravel soil with aeolian sand in typical desert highway construction. Comprehensive laboratory experiments were conducted to evaluate the physical and mechanical properties of both materials. The results indicate that although aeolian sand exhibits high shear strength and permeability, it poses compaction challenges due to poor particle gradation. The engineering parameters applied in the finite element numerical simulation model were systematically verified through field tests and compared with experimental results. It is used to simulate the behavior of aeolian sand, focusing on predicting foundation settlement and embankment slope stability under different compaction conditions. The analysis identifies the key factors influencing roadbed settlement and slope stability under applied loads. Based on these findings, the study offers theoretical guidance for optimizing the application of aeolian sand in desert road construction, aiming to reduce costs and logistical difficulties while ensuring a stable and durable roadbed.