Numerical simulation and strength prediction model of mechanical properties of rock mass with different single joint occurrences

The mechanical properties of jointed rock are of great significance to the long-term stability of various rock mass projects, and the mechanical properties of rock are greatly affected by the occurrence of joints, and even play a decisive role. In order to study the influence mechanism of joint occurrence on rock strength and failure mode, the uniaxial compressive strength of rock is accurately predicted based on joint occurrence parameters. PFC software is used to establish a numerical model of rock with different single joint occurrence, and a series of uniaxial compression numerical simulation tests are carried out. The influence of joint size and joint dip angle on the mechanical properties of rock is obtained: With the increase of joint size, the failure mode of rock gradually changes from shear failure along a certain angle to crack propagation failure at the joint end, and the uniaxial compressive strength gradually decreases. When the joint dip angle is less than the internal friction angle, the uniaxial compressive strength of the rock decreases gradually with the increase of joint dip angle, and the failure mode is mainly the crack propagation failure at the joint end. When the dip angle of the joint exceeds the internal friction angle, the uniaxial compressive strength of the rock gradually increases, and the failure mode is mainly the shear failure of cutting rock or secondary crack propagation along a certain angle. On this basis, a prediction model of uniaxial compressive strength of single jointed rock is proposed based on the theory of damage mechanics and fracture mechanics. The influence of different failure modes caused by the difference of single joint occurrence on the strength of rock is fully considered, and the model parameters are easy to obtain. The example shows that the model has high precision and can meet the requirements of engineering site.