Energy Dissipation and Damage Evolution Characteristics of Shale under Triaxial Cyclic Loading and Unloading

Rock engineering is highly susceptible to cyclic loads resulting from shale gas exploitation; it very important study the failure mechanism of underground rock mass under load. To investigate energy dissipation and damage evolution characteristics triaxial loading unloading conditions, a series incrementally tests different confining pressures (10 MPa, 15 20 30 MPa) were carried out. The variation plastic strain four was analyzed, dissipated ratio discussed. results show that: peak strength increase with in pressures. Meanwhile, increases rapidly first, then develops steadily, finally sharply axial strain. ratio-strain curve presents spoon-shaped feature, can be divided into three stages: linear decline stage, steady development rapid respectively. However, trend elastic modulus opposite that ratio. Accordingly, regarded as factor describe degradation shale. Based on energy, theoretical equation stress-strain established. By substituting test data formula, found calculated are basically consistent data, strains stress by good agreement data. findings could provide support for analysis process conditions.