Experimental study on dynamic impact resistance of new NPR bolt support

The excavation of deep caverns can result in significant nonlinear large deformations caused by dynamic impact effects, such as high-stress rock bursts, impact ground pressure, or external explosions. To address this issue, a research team led by Academician He Manchao has developed a new 2G-NPR (Second Generation Negative Poisson’s Ratio) bolt material with the characteristics of uniform large deformation, obvious disappearance of necking, and disappearance of yield platform. On this basis, a large deformation control technique for the rigid-flexible structural systems of rock supported by the 2G-NPR bolt has been developed. To provide a basis for the application of 2G-NPR bolt support in national defense and civil air defense engineering, this study investigated the overall dynamic response law and mechanical behavior of the 2G-NPR bolt support engineering rock mass under the strong impact of explosions. The attenuation model of explosion shock wave in granite was studied in the explosion test site and the charging parameters required for explosion were determined. The support parameters of the PR bolt support composite structure and the 2G-NPR bolt support composite structure cavern were obtained. The dynamic response and interaction law of the peak pressure of the arch crown, the acceleration of the arch crown, the axial force of the anchor rod and the surrounding rock in the two different supporting systems were studied and compared. Impact and explosion resistance characteristics and failure modes of the different supporting caverns were revealed. The results indicate that the 2G-NPR bolt can resist stronger plane impact load with a higher energy absorption share and more significant energy absorption characteristics in underground explosion-proof support, and can play a supporting and protection effect that traditional bolt support cannot match. Moreover, the cavern excavation stress compensation theory for the change of surrounding rock stress state caused by underground cavern excavation was proposed and the theoretical solutions of stress components and displacement components at the anchorage end of bolt were studied, which provides a theoretical reference for subsequent cavern support research.