Experimental Research On Damage Evolution And Fail Of Granite Under Unloading Confining Pressure

By studying the mechanical behaviors of rocks under confining pressuring unloading conditions, analyses have been made on the influence of the unloading rate of confining pressure on the properties of the rock. Special loading and unloading methods are designed to compare the mechanical properties of the rock in loading and unloading confining pressure. The rock failure is studied from two aspects:energy and damage. Then a rock failure criterion is established based on the method of probability. The rock failure criterion, which can reflect the influence from the loading and unloading rate, is established on the basis of Mohr-Coulomb failure criterion and the experimental data. A constitutive model, which reflects the rock failure, is established on the basis of the volumetric strain of the rock. The model is used to study the unloading rate of confining pressure on rock failure and the difference between the axial loading and the confining pressure unloading. The 3D viscoelastic model is adopted to analyze the damage on rock's viscoelasticity. By studying the energy absorption, deformation, elasticity modulus of the rock in cyclic loading and unloading of confining pressure, the thesis analyzes the damage of different unloading rates of confining pressure on the rock.