The tensile and shear properties of plant roots are important factors that determine their slope protection and are also direct indicators for evaluating plant roots for slope protection. In order to explore the soil-fixing properties of root system and root–soil composite of Indigofera amblyantha and Cassia bicapsularis, the high and steep slope of Zhaofu quarry in Wudang District of Guiyang City was taken as the research background. The effects of root diameter, tree species, root water content and normal pressure on the tensile properties of single root, direct shear friction of root system and shear properties of root–soil composite were investigated by an indoor mechanical test and a direct shear friction test. Results showed that under saturated water content, the tensile strength of C. longifolia decreased, and the tensile strength of C. bifolia also decreased. With the increase in water content from 10.3% to 22.3%, the friction strength of the root–soil interface increased gradually, and the friction strength of root–soil interface of Cassia bicapsularis was greater than that of Cassia longifolia. With the increase in root diameter, the root–soil interfacial friction strength of the two shrubs increased slightly. The normal pressure also increases the density of the soil, so that the roots give full play to the reinforcement effect. The greater the normal pressure, the greater the shear strength of the root–soil composite. When the water content increased from 10.3% to 22.3%, the shear strength of the two-shrub root–soil composites increased first and then decreased gradually, reaching the maximum at 14.3%, followed by the shear strength at 10.3%, reaching the minimum at 22.3%.

In order to explore the mechanical response characteristics of fractured sandstone under true triaxial different medium principal stresses, matdem particle flow software was used to study the mechanical response characteristics, fracture mechanism and damage evolution characteristics of sandstone specimens under the conditions of 30 MPa, 40 MPa and 50 MPa respectively. The simulation results are verified by true triaxial test. The results show that under true triaxial stress, the increase of medium principal stress is beneficial to increase the strength of sandstone. The fracture degree of the specimen increases with the increase of the intermediate principal stress, and finally the interlacing macroscopic cracks are formed. When the intermediate principal stress is perpendicular to the fracture strike, the fracture mode of sandstone is that the macroscopic fracture plane is perpendicular to the fracture strike, and the fracture mechanism of sandstone under true triaxial compression is mainly shear failure, accompanied by tensile failure. With the increasing of the intermediate principal stress, the fractal dimension of the fracture of sandstone specimen increases significantly and the degree of fracture deepens. Combined with the true triaxial test results, the rationality of particle flow simulation test is proved.

The Journal retracts the article entitled “Study on Mechanical Properties of Soil Stabilization by Different Vegetation Roots on High Steep Slope” by Ding et al.