Experimental Investigation on Mechanical Properties of Sandstone in Three Gorges Reservoir Area under Unloading Condition

摘要

Test results show that unloading failure is more brittle than loading failure, and rock samples suffer more damage under unloading failure, especially in high stress. Unloading failure leads to deterioration of deformation modulus, internal friction angle, and cohesion, whose values changes with the changing of stress state. Unloading stress-strain curves of sandstone samples could be divided into four stages, loading stage, unloading stage, brittle stress drop stage, ideal plastic stage, and well fitted by polynomials. There is springback deformation in the second stage, which decreases with increase of initial confining pressure. These test results could offer theory support for analysis of deformation and stability of actual projects.