Hydro-mechanical effects of vegetation on slope stability: A review.

This study explores the complex interplay between vegetation and soil stability on slopes to enhance soil-bioengineering and slope stabilization techniques. We assess the multifaceted role of vegetation in soil stabilization, examining processes such as canopy interception, stemflow, and the effects of hydrological and mechanical changes induced by root systems and above-ground plant structures. Key underlying mechanisms and their effects on stability are reported, along with the evaluation of significant plant indicators from historical research. Our review revealed that plant coverage and root architecture are critical in reducing soil erosion, with plant roots increasing soil cohesion and reducing soil detachability. Above-ground vegetation provides a protective layer that decreases the kinetic energy of raindrops and allows for higher infiltration. The importance of species-specific root traits is emphasized as pragmatic determinants of erosion prevention. Additionally, the effects of root reinforcement on shallow landslides are dissected to highlight their dualistic nature. While root-soil interactions typically increase soil shear strength and enhance slope stability, it is crucial to discriminate among vegetation types such as trees, shrubs, and grasses due to their distinct root morphology, tensile strength, root area ratio, and depth. These differences critically affect their impact on slope stability, where, for instance, robust shrub roots may fortify soil to greater depths, whereas grass roots contribute significantly to topsoil shear strength. Grasses and herbaceous plants effectively controlled surface erosion, whereas shrubs mainly controlled shallow landslides. Therefore, it is vital to conduct a study that combines shrubs with grasses or herbaceous plants. Both above-ground and below-ground plant indicators, including root and shoot indicators, were crucial for improving slope stability. To accurately evaluate the impact of plant species on slope stability reinforcement, it is necessary to study the combination of hydro-mechanical coupling with both ground plant indicators under specific conditions.

Quality evaluation of ground improvement by deep cement mixing piles via ground-penetrating radar.

Deep cement mixing piles are a key technology for treating settlement distress of soft soil subgrade. However, it is very challenging to accurately evaluate the quality of pile construction due to the limitations of pile material, large number of piles and small pile spacing. Here, we propose the idea of transforming defect detection of piles into quality evaluation of ground improvement. Geological models of pile group reinforced subgrade are constructed and their ground-penetrating radar response characteristics are revealed. We have also developed ground-penetrating radar attribute analysis technology and established ground-penetrating radar technical system for evaluating the quality of ground improvement. We further prove that the ground-penetrating radar results integrating single-channel waveform, multi-channel section and attributes can effectively detect the defects and stratum structure after ground improvement. Our research results provide a rapid, efficient and economic technical solution for the quality evaluation of ground improvement in soft soil subgrade reinforcement engineering.

Experimental study on shear strength of saturated remolded loess.

Loess has the characteristics of large porosity, loose structure, uniform composition and strong collapsibility. When encountering heavy rainfall and irrigation prone to saturation, resulting in loess landslides, roadbed subsidence and dam instability. In order to study the effect of dry density and shear rate on the shear strength of saturated remolded loess, the consolidated undrained (CU) test was carried out in Yan'an City by using SLB-6A stress-strain controlled triaxial shear permeability test instrument. The shear rate, confining pressure and dry density were controlled during the test. The dry densities of the samples were 1.5 g / cm3, 1.6 g / cm3 and 1.7 g / cm3, respectively. CU tests of saturated remolded loess were carried out at different shear rates under the confining pressures of 100 kPa, 150 kPa and 200 kPa, respectively. It is found that the stress-strain curve of saturated remolded loess gradually moves upward with the increase of dry density. With the increase of dry density, the cohesion and internal friction angle of remolded saturated loess samples increase. At the same shear rate, with the increase of dry density, the deviatoric stress of the specimen increases significantly.

Research on crack evolution law and macroscopic failure mode of joint Phyllite under uniaxial compression.

In order to explore the fracture mechanism of jointed Phyllite, the TAJW-2000 rock mechanics test system is used to carry out uniaxial compression tests on different joint inclination Phyllites. The influence of joint inclination of Phyllite failure mode is discussed, and the progressive failure process of Phyllite is studied. The test results show that the uniaxial compressive strength anisotropy of jointed Phyllite is remarkable. As the inclination increases, it exhibits a U-shaped change; When 30° ≤ α ≤ 75°, the tensile and shear failures along the joint inclination mainly occurs. the joint inclination controls the failure surface form of the Phyllite; The crack initial stress level of the joint Phyllite is 0.30-0.59σf, the crack failure stress level is 0.44-0.86σf. When α = 90°, the σcd value is the largest, and σcd with α = 90° can be used as the maximum reliable value of uniaxial compressive strength of Phyllite. Using the theory of fracture mechanics, it is analyzed that under uniaxial compression of the rock, the crack does not break along the original crack direction, but extends along the direction at a certain angle to the original crack. The joint effect coefficient is proposed to show the influence of the joint inclination on the uniaxial compressive strength of the phyllite. Both the test and simulation results show that when the joint inclination is 60°, the joint effect coefficient is the largest. The compressive strength is the smallest. Numerical simulation analyses the crack evolution law of phyllite under different joint inclination under uniaxial compression, which verifies that there are different failure modes of joint phyllite under uniaxial compression.

Coupling of electrochemical-temperature-mechanical processes in marine clay during electro-osmotic consolidation.

Electro-osmotic consolidation has been applied in several geotechnical engineering applications that contain a series of complex processes, including electrochemical processes, temperature changes, and mechanical evolution. To explore the combination of electrochemical-temperature-mechanical processes in marine clay, electro-osmotic consolidation experiments were conducted using a self-made electro-osmotic consolidation system under various durations and voltages. The following findings was obtained: (1) the change in the pH value increased during electro-osmotic consolidation and as the voltage rise; (2) the temperature increased with a rise in voltage in the initial stage of the experiments, which was induced by Joule heating; (3) the temperature rise promoted the electro-osmotic consolidation process, which included a rise in the coefficient of consolidation and a reduction in water content; (4) horizontal shrinkage occurred when the horizontal stress increment was greater than the critical stress condition. In addition, the volume difference reached a constant value, and was proportional to the voltage rise. After the discussion, a coupling analysis was conducted, which can help to better understand the mechanism of electro-osmotic consolidation and can provide reference for engineering applications.