Experimental Investigation of the Fracture Performance of Hard Rock with a Single Borehole by Using a Hydraulic Splitter

The continuous expansion of urban areas is severely restricted by limited land resources. A promising and universal solution to this problem is the development of underground spaces. However, during the excavation of underground rock tunnels, mechanical tools undergo severe wearing due to the strengthened mechanical properties of the rock. Engineering applications have demonstrated that hydraulic splitters can effectively fracture hard rocks. Therefore, in this study, the effect of the rock compressive strength, confining pressure, and borehole margin on the rock fracture performance was experimentally investigated. The hydraulic splitter can be effectively applied to fracture hard rock. The peak fracture pressure increases with the increase in the rock compressive strength, confining pressure, and borehole margin. Moreover, the peak fracture pressure under a bidirectional unequal stress confining pressure is lower than that under bidirectional equal stress, and the difference between these pressure values gradually decreases as the confining pressure increases. The peak fracture pressure with the free surface is lower than that without the free surface, which demonstrates that the presence of the free surface can alleviate the difficulty in realizing rock fracturing.