Study on rock visco-elastic plasticity analysis and yield criterion ofwater and rock interaction

In order to describe the creep features of the rock under different pore water pressure, a MTS815.02 rock testing machine was applied to have a fluid-solid coupling creep test of the saturated sandstone and according to the improved Druck-Prager Yield Function, the creep constitutive model of the rock was conducted. The study result showed that under the joint function of the effective stress and time, the strength parameters would be continuously deteriorated. Generally the cohesion strength was reduced by 16.89% and the internal friction angle was reduced by 7.93%. Under the external loading, the rock failure was mainly caused by the reduction of the cohesion strength. Therefore in the engineering practices, to prevent the failure and damage of the surrounding rock should control the cohesion strength and secondary should consider the control of the internal friction angle variation. Finally according to the improved Druck-Prager yield parameters, the creep constructive model of the rock was established as for describing on the rock attenuation creep, stable creep stage and accelerated creep.The fitting coefficients of the fitted curve and the experimental curve would be both above 0.95.