Analysis of seepage evolution law of rock mass based on the numerical algorithm considering strength weakening water absorption

Abstract

Conventional numerical methods for modeling water seepage hardly provide a realistic description for the associated degradation of rock material and the permeability evolution mechanism. A numerical algorithm was utilized to investigate the rock seepage evolution process and the course of deformation failure. A theoretical model for depicting the weakening of rocks modulus and strength caused by water absorption in rock substrate was developed, and the mathematical relationships are presented in this paper. The softening process of a siltstone specimen due to water absorption was simulated under low- and high-fluid pressures as the boundary condition based on the theoretical model. Moreover, uniaxial compression test was performed for the specimen under different time of water absorption. The results indicated that the higher the fluid pressure, the quicker that the rock specimen reached saturation. It was observed that at the beginning of a seepage process, the openings are mainly filled by free water, but as time proceeds, there is a transition from absorption of free water in openings to water absorption by rock substrate. Fluid pressure, as the boundary condition, has a controlling effect on seepage rate but barely has any effect on the rate of water absorption in rock substrate. As the time of water absorption increases, rock strength (cohesion and angle of internal friction) decreases gradually until reaching the residual value. The numerical estimation of the changes in water content of rock substrate over time agrees with the theoretical explanations, which indicates high precision of the developed numerical method.