Study On Influence Of Intermediate Principal Stress On Engineering Rock Mass Failure Behavior

The stress environment in which rocks are located true triaxial state.It is of great significance to study the mechanical behavior of engineering rocks under different stress conditions,especially different intermediate principal stresses.In this paper,the elastic-plastic cellular automata EPCA3 D simulation system,a CASRock software series module independently developed by Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,is used to carry out a series of simulation analysis on the fracture process of heterogeneous rock and the stability of engineering rock mass under different stress conditions.The deformation,strength and damage failure characteristics of heterogeneous rock under three-dimensional compression are studied.Based on the heterogeneity and strength nonlinear characteristics of rock materials,the rock strength criterion considering heterogeneity is established,and the influence of different intermediate principal stresses on the stability of tunnel surrounding rock is studied.The main work and research results are as follows:(1)Numerical simulation of true triaxial compression fracture process of heterogeneous rock is carried out,and the typical experimental phenomenon is reproduced,namely,the strength of rock sample increases with the increase of minimum principal stress,increases first and then decreases with the increase of intermediate principal stress,and the acoustic emission curve shows the phenomenon of divergence-convergence-divergence.At the same time,it is found that in the process of increasing the intermediate principal stress,there is a phenomenon that the rock strength in a certain range of intermediate principal stress remains unchanged or the fluctuation range is small,and the range gradually expands with the increase of the minimum principal stress level.(2)Based on numerical experiments,the strength criterion of heterogeneous rocks is established,which depends on the homogeneity coefficient.Meridian surface function has clear physical concept,and five mutually independent material parameters have clear physical significance.The criterion reflects that the better the rock homogeneity is,the higher the triaxial compressive strength is,and the more deviated from the p axis in the q-p stress space,the higher the linearity is.The numerical test results under different homogeneity coefficients also verify the interval effect of the intermediate principal stress,the meridian plane function has a good fitting effect,and the numerical simulation results on the ? plane are in good agreement with the selected corner function,which verifies the rationality of the established strength criterion.(3)Numerical analysis of excavation process of engineering rock mass tunnel is carried out.The results show that the direction of intermediate principal stress has an important effect on the mechanical behavior of tunnel surrounding rock.The closer the weak interlayer is to the tunnel boundary,the greater the influence is on the mechanical behavior of surrounding rock.The surrounding rock between the tunnel and the weak interlayer is more likely to be destroyed when the inclination angle of the weak interlayer is between 45 and 60 degrees.The rotation direction of the main stress axis of the surrounding rock is mainly parallel to the direction of gravitational acceleration(xoz,yoz plane)and the rotation degree is smaller on the plane perpendicular to the direction of gravitational acceleration(xoy plane).