Experimental study on compression characteristics of fractured soft rock and its Mohr-Coulomb criterion

In order to fully understand the influence of fracture on deformation and failure of soft rock, and the application of fractured soft rock to practical engineering. Cement mortar specimens were prepared and used to simulate soft rock based on the principle of similarity. The stress-strain relationship and failure mode of soft rock with different fracture angles and connectivity were studied using uniaxial and triaxial compression tests, and the constitutive model of soft rock and its Mohr-Coulomb failure criterion was established. The results show that compared with intact soft rock, the uniaxial compressive strength of fractured soft rock was low. However, no significant difference was observed in the stress-strain curves, although varying the fracture angles had signif-icant effects on the failure mode of the soft rock specimen. The Boltzmann model and GaussAmp model were used to describe the ascending and descending sections of the uniaxial compressive stress-strain curve of soft rock, respectively, and the constitutive model was in good agreement with the experimental results. The Mohr-Coulomb failure criterion of soft rock under the conditions of the second and third groups of equal stress is established using the triaxial compression test results, which shows that the fracture has a significant influence on the cohesion of soft rock, but little influence on the internal friction angle.