Energy Evolution and Damage Characteristics of a Fissured Rock Mass under Stable Hydraulic Pressure during Cyclic Loading

Abstract Deep, long tunnels are often associated with long-term stable seepage pressure, which is easily induced by repeated loads during tunnel construction, resulting in water and mud inrush accidents. To explore the fracture failure mechanism of the rock mass water-inrush disaster process under the influence of construction disturbance during the excavation of deep and long tunnels, a cyclic loading test of fissured rock mass under stable hydraulic pressure was carried out using a self-developed stable hydraulic pressure device. First, the cyclic loading results of fissured rock mass under stable seepage pressure were analyzed. Second, based on irreversible strain, the damage variables of the rock mass in each cyclic stage were defined. It increases with increasing cycle number and decreases with increasing fissure inclination angle, and the change is more pronounced under stable hydraulic pressure. Subsequently, the dissipated energy, elastic strain energy, and total energy generated during cyclic loading of a fissured rock mass under various conditions were calculated, and the energy evolution mechanism during cyclic loading was analyzed. Finally, based on the energy criteria and experimental conditions, the damage variables of the rock mass were defined. The characteristics of damage variables, as defined by irreversible strain and energy criteria during loading, were analyzed.