Experimental Study And Numerical Analysis On Post-peak Mechanical Poperties Of Sandstone Under Fluid-solid Coupling

In the complex geological environment,the surrounding rock has obvious difference with the mechanical properties of the plastic material.Under the external force,the stability of the surrounding rock reaches a certain degree,and its stability decreases sharply,especially under the influence of pore water pressure,and then reaches the peak stress Destabilization damage into the residual stage,the rock also has a certain strength but failed to meet the actual engineering strength requirements,will lead to roadway collapse caused by engineering accidents.Therefore,it is necessary to study the mechanical properties of the rock after the post-peak strain softening stage.Based on the method of experimental study,theoretical analysis and numerical analysis,this paper applies the MTS815.02 rock mechanics test system to study the evolution of the whole process of creep-catastrophe in the deep rock mass,which is based on the National Natural Science Foundation of China.In this paper,the mechanical properties of sandstone under fluid-solid coupling are discussed,and the variation law of sandstone after peak-flow is explored,and the mathematical expression of elastic modulus after peak is obtained.And the numerical analysis was carried out.The main research work is as follows:The basic mechanical properties and deformation parameters of the sandstone were obtained by the triaxial compression test of the sandstone under fluid-solid coupling.The deformation stress of the peak stress and the participating strength with the pore water pressure and the peak Stress and participation intensity with the confining pressure deformation law.The effective stress principle of sandstone is analyzed and the effective peak intensity of sandstone is analyzed.The influence of pore water pressure on the effective stress and residual strength of sandstone is discussed.A model of subsequent yield surface considering pore water pressure is established.Generalized cohesion and generalized internal friction angle and pore water pressure,strain softening parameters of the three-dimensional surface.Based on the Mohr-Coulomb basic principle,the basic assumption of the post-peak strain softening stage is introduced,and the effective stress principle is introduced.The elastic modulus of the sandstone after the post-peak strain is derived by the basic elementary transformation and the inverse of the function parameters.The experimental results show that the experimental curve and the numerical simulation curve are close to each other and the residual strength is basically consistent.The correctness of the strain softening model is further verified by numerical simulation.The results show that the experimental results show that the strain softening model is well fitted to the FLAC^3D.