Effect of interfacial characteristics on dynamic splitting behavior of quasi rock-concrete composite layer: Towards resilient tunnel support against rock burst

Using shotcrete as lining supports can effectively prevent tunnels from the rock burst of the surrounding rock, while rock-concrete interfaces play key roles in determining the supporting effect. In the present study, both experimental and numerical efforts are made to quantify the effect of joint roughness coefficient (i.e., JRC ranging from 4 to 20) and interface shape (i.e., wave, triangle and ladder-shape) on the dynamic splitting properties of rock-concrete composites. The results show that the dynamic tensile increase factor of the quasi rock-concrete interface increases with the increase of JRC, but the variation of interface shape has a minor effect over the stress rate ranges of 21.95 and 88.14 GPa/s. Specifically, the dynamic tensile strength and dissipated energy of the rock-concrete composites increase by up to 79.25% and 42.59%, respectively, with the increase of JRC from 4 to 20, as more concrete hydration products can fill the interface cavities and result in a better bonding effect. In addition, the numerical results reveal that the composite interface exhibits confined tension failure when exposed to dynamic splitting tension, and the enhanced confining effect at higher JRC increases the shear strength of the interface. Overall, the findings can give a basis for optimizing the interfacial characteristics between rock and shotcrete against rock burst.