Experimental Study on Static Shear Characteristics of Completely Weathered Muddy Siltstone Lying under Tunnel

The properties of completely weathered argillaceous siltstone are between soil and rock. Due to its long-term settlement under traffic cyclic load is smaller than that of soft soil, it is often regarded as rock material and thus has less research on cumulative deformation. However, after investigation, it is found that the highly weathered soft rock has a great influence on the deformation-sensitive structures such as subway shield tunnel. Hence, it is necessary to conduct a more in-depth study on the mechanical properties of completely weathered argillaceous siltstone. By analyzing the undrained static shear strength of the rock sample under different test conditions (consolidation mode, water infiltration, and different confining pressure), and drawing the critical state line, the structural characteristics of the rock sample are understood. The results show that: The failure deviatoric stress and peak pore water pressure of rock sample under K₀ consolidation are higher than those under isotropic consolidation, indicating that the consolidation mode has a significant effect on the stress-strain and pore water pressure of the completely weathered argillaceous siltstone. Under the same test conditions, the failure deviatoric stress and peak pore water pressure of the samples increases linearly with the increase of the consolidation pressure. After water infiltration treatment, the effective stress of the rock sample decreases, the shear strength reduces, and the degree of damage intensifies.