Time-dependent behavior of saturated silty mudstone under different confining pressures

Abstract

The long-term stability of rock slopes is greatly affected by the creep behavior of rock mass. This study presents the creep behavior of a saturated silty mudstone that is from the Three Gorges Reservoir in China. Triaxial compression tests and triaxial creep tests were performed on the silty mudstone under different confining pressures. The test results show that the creep behaviors have three stages, namely, the primary creep stage, steady-state stage, and accelerated creep stage when the deviatoric stress is higher than the yield stress of the silty mudstone. The steady-state creep strain rate of the silty mudstone increases with the increment of the axial deviatoric stress. Partial reversals of the axial creep strain curve are found under the confining pressure of 1 MPa and 5 MPa, which may be caused by the expansion of illite minerals after being infiltrated by water in the rock voids. Based on the experimental data of the silty mudstone and the fractional calculus theory, a nonlinear creep model that describes the creep behaviors of the silty mudstone is proposed. The theoretical creep curves obtained from the creep model are in good agreement with the experimental data.