Transition Threshold of Granite Mechanical Characteristics at High Temperature

No unified criterion exists for the transition threshold of rock mechanical characteristics. We combine rock stress-strain curves to propose an increment ratio of axial pressure based on uniaxial compression tests on granite at high temperature. The behavior of the increment ratio of strain, elastic modulus, Poisson's ratio, and energy with axial pressure is analyzed, and the following conclusions are drawn. (1) High temperatures aggravate rock deterioration, reduce failure strength, and enhance ductility characteristics. (2) Under loading, the compression-to-elasticity and elasticity-to-plasticity transition thresholds for rock occur, respectively, at 20%-35% and 75%-80% stress levels at temperatures of 25-800 degrees C. (3) The source data for calculating rock deformation parameters or unloading points for unloading tests can be selected over the stress level range of 35%-75%.