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

In deep hot dry rock formations, natural fractures are widely distributed and significantly influence the deformation and failure behavior of rock masses. While previous research has primarily focused on the mechanical responses of intact rocks under high-temperature and high-pressure conditions, the elastic-plastic deformation and failure mechanism of hot dry rock containing prefabricated fractures remains inadequately understood. This study systematically investigates the elastic-plastic deformation and failure characteristics of hot dry rock with prefabricated fractures under high-temperature and high-pressure conditions using a pore-permeability analyzer, thermal conductivity meter, spontaneous imbibition apparatus, and a high-temperature, high-pressure triaxial compression system, integrated with computed tomography scanning, ultrasonic velocity monitoring, and nuclear magnetic resonance. The results reveal that the presence of prefabricated fractures weakens overall rock strength; however, compressive strength increases with fracture inclination angle. Additionally, the rock's elastic-plastic deformation capacity is enhanced with increasing dip angle. Energy analysis shows that although the total energy, elastic strain energy, and dissipated energy of fractured rocks are lower than those of intact rocks, all three parameters increase with greater fracture inclination. Regarding damage factors, the weakening effect of prefabricated fractures on rock decreases as the fracture dip angle increases. Regarding the failure mode, rocks with prefabricated fractures predominantly exhibit splitting failure. In conclusion, these findings provide a theoretical basis for understanding the elastic-plastic deformation and failure behavior of hot dry rock with prefabricated fractures under high-temperature and high-pressure conditions.