Non-Uniform Shear Deformation and Its Influence Factor Sensitivity of Colluvial Coarse-Grained Soil

To investigate the mechanical properties of coarse-grained soil in high-altitude mountainous areas, experimental research was conducted to explore the shear process, shear modulus, shear dilation, and stress axis rotation of coarse-grained soil under varying conditions. The sensitivity and mechanisms of these factors were also analyzed. The results indicate that increasing water content and fine particle content significantly diminish the strain-hardening characteristic, whereas dry density and normal stress augment this effect. Under shear stress, the samples exhibit pronounced non-uniform shear dilatancy. Elevated water content, fine particle content, and normal stress enhance shear contraction at the rear of the sample while suppressing shear dilation at the front. In contrast, dry density produces the opposite effect. The rotation of the stress axis initially follows a nonlinear growth pattern before transitioning to linear growth. The growth rate and ultimate rotation angle increase monotonically with water content, fine particle content, and normal stress but decrease with increasing dry density. Additionally, the shear modulus decreases exponentially with increasing water content and increases exponentially with dry density, fine particle content, and normal stress. Ultimately, normal stress is identified as the most sensitive factor, followed by dry density and fine particle content, with water content being the least sensitive. These findings can provide geotechnical parameters and a theoretical basis for the scientific prevention of high-altitude geological hazards. These findings can provide indoor mechanical parameters and deformation laws of coarse-grained soils for engineering.