Energy Action Mechanism of Reinforced Sandstone under Triaxial Cyclic Loading and Unloading

In underground engineering, reinforcement is a necessary means to ensure the stability of surrounding rock. Due to the stress redistribution caused by excavation disturbances, the reinforced rock mass is frequently subjected to loading and unloading, and its mechanical properties change accordingly. Based on the above engineering practice, using pasted circular CFRP, an approximate simulation of the rock reinforcement effect of bolt and shotcrete support was performed. Triaxial cyclic loading and unloading tests of reinforced sandstone were carried out, and the influence of different reinforcement schemes on the mechanical properties was compared and analyzed. Furthermore, the strengthening mechanism, damage evolution, and energy transformation mechanism of CFRP are discussed. The results showed that the peak strength increased about 14.2% and 23.8% with the two reinforced schemes, and the residual strength increased about 27.3% and 52.8% with the increase in the area reinforced by CFRP. Under the same confining pressure and strain conditions, the characteristic energy density and elastic energy ratio increased with an increase in the reinforcement area, but the damage variable decreased. It is proved that CFRP can improve energy absorption efficiency, enhance the energy storage limit, and reduce dissipation efficiency. By inhibiting the propagation of internal fissures and limiting the energy dissipation during fractures, the rock mass can be restrained and strengthened.

Automated summary

Reinforcement is essential in underground engineering to ensure the stability of surrounding rock. This study simulated the rock reinforcement effect of bolt and shotcrete support using pasted circular CFRP. Triaxial cyclic loading and unloading tests were conducted on reinforced sandstone to analyze the impact of different reinforcement schemes on mechanical properties. The results showed that CFRP can improve peak and residual strength, enhance energy absorption efficiency, and reduce dissipation efficiency of the rock mass.