Effect of Bilinear Mohr-Coulomb Model and Tensile-Compression Ratio on Rock Fracture

The compressive strength of rock mass is several times to tens of times its tensile strength, and the stress field of the crack tip of rock mass is mainly tensile shear. Therefore, the tensile-compression ratio of rock is very sensitive to crack propagation of rock mass. Firstly, the numerical difference software FLAC3D is used to establish the bilinear Mohr-Coulomb strength criterion, which considers the macroscopic local performance of far-field displacement and fixes the cracking direction of the unit. Then, the theoretical solution of the bilinear constitutive model and the Hoek-Brown model is compared, and the existing uniaxial compression test simulation of fracture-containing cement mortar verifies the effectiveness of the numerical means. Finally, the crack propagation of rock masses with different tensile-compression ratios is studied. The results show that the bilinear strength criterion requires fewer parameters to be measured than the H-B criterion, and more accurately reflects the rock strength failure, especially the tensile shear failure, compared with the linear Mohr-Coulomb strength criterion. In the uniaxial compression numerical test of fractured rock mass, the compressive strength of rock mass increases with the increase of tensile compression ratio, and the failure form of rock mass is quite different.