Simulation Study Of Multiple Cracks Propagation In Rock Based On Extended Finite Element Method

There are cracks with different shapes,lengths and distribution characteristics in natural rock masses or rock masses subjected to external loads during mining.In order to study the influence of initial cracks on the crack propagation law and rock mass characteristics when the rock mass is subjected to external loads,this paper is based on the extended finite element method(XFEM),using ABAQUS finite element software to analyze the compression process of the prefabricated collinear double cracked rock mass.The inclination angle of prefabricated collinear double cracks,the length ratio of prefabricated main cracks and secondary cracks,the influence of compressive stress state on crack propagation characteristics,cracking stress and rock mass strength were analyzed.And the crack propagation characteristics of the prefabricated random cracked rock mass during the compression process and its influence on the strength of the rock mass.The main contents and conclusions of this paper are as follows:(1)The extended finite element method is used to simulate the uniaxial compression and biaxial compression of the prefabricated collinear double-cracked rock mass..When the crack inclination angle is less than or equal to 45°,the crack propagation is dominated by wing cracks,and the crack propagation direction tends to the direction of the compression principal axis.When the crack inclination angle is greater than 45°,the crack propagation is dominated by secondary coplanar cracks.At 90° inclination,the crack did not propagate significantly.With the increase of the inclination angle,the cracking stress and critical strain of crack propagation gradually increase.Under the condition of biaxial compression,the change of the stress state causes the cracking stress to be higher than that in uniaxial compression,and the increase of the cracking stress increases with the increase of the inclination,and the strength of the rock mass also increases accordingly.(2)Use the superposition method to calculate the stress intensity factor,under the condition of the same inclination angle,the type I and II stress intensity factors of the main crack in the prefabricated collinear double crack are less affected by the ratio of the length of the primary and secondary cracks.The type I and II stress intensity factors decrease significantly with the increase of the ratio of primary and secondary crack lengths.Under the condition of the same primary and secondary crack length ratio,the type II stress intensity factors of the primary and secondary cracks first increase and then decrease with the increase of the inclination angle.Under the condition of an inclination angle of 45°,the type II stress intensity factor is the largest.(3)The extended finite element method is used to simulate the uniaxial compression process of the rock mass with pre-fabricated random cracks,and the results show that the propagation of the main crack is significantly affected by the secondary cracks.With the increase of the inclination angle of the main crack,the extent of the main crack's growth gradually weakened.When the line connecting the tips of the secondary cracks approaches the direction of the compression principal axis,the secondary cracks are likely to form a penetration.When the inclination angle of the main crack is less than or equal to 45°,the secondary cracks at the edge expand less.When the inclination angle of the main crack is greater than or equal to 45°,the secondary cracks at the edge expand significantly,and the upper and lower secondary cracks form a through.