Elastic–Plastic Deformation and Failure Mechanisms of Hot Dry Rock Containing Prefabricated Fractures: An Experimental Study

Abstract In deep hot dry rock formations, the widespread occurrence of natural fractures significantly affects the deformation and failure behaviors of the rock mass. While previous research has primarily focused on the mechanical behavior of intact rock under high-temperature and high-pressure conditions, the underlying mechanisms of elastic–plastic deformation and failure in hot dry rock containing preexisting fractures remain insufficiently investigated. This study provides an in-depth analysis of the elastic–plastic deformation and failure characteristics of hot dry rock with prefabricated fractures under high-temperature and high-pressure environments. The research employs advanced experimental techniques, including pore-permeability analysis, thermal conductivity measurement, spontaneous imbibition, and high-temperature, high-pressure triaxial compression testing, complemented by methods such as computed tomography scanning, ultrasonic velocity monitoring, and nuclear magnetic resonance. The results indicate that the presence of preexisting fractures reduces the overall strength of the rock, but compressive strength increases as the fracture inclination angle increases. The rock's elastic–plastic deformation capacity also increases with the dip angle. Energy analysis reveals that, although the total energy, elastic strain energy, and dissipated energy of fractured rocks are lower than those of intact rocks, all three parameters show an increasing trend with higher fracture inclination. In terms of damage factors, the weakening effect of prefabricated fractures on the rock diminishes as the fracture dip angle increases. Regarding failure modes, rocks with prefabricated fractures predominantly exhibit splitting failure. These findings enhance the theoretical understanding of the elastic–plastic deformation and failure behaviors of hot dry rock with preexisting fractures under high-temperature and high-pressure conditions.