Re-fracture process and mechanical characteristics of cracked rock samples

Most of the rocks surrounding deep underground construction consists of cracked rock. The deformation of the surroundings is complicated, and not only involves slipping, but also involves re-fracturing. Available results in conventional uniaxial and triaxial experiments of rock samples can be used to analyze deformations of supports and surrounding rocks on underground constructions, but they cannot reflect the evolution of the re-fracture processes and the mechanical characteristics of the cracked surrounding rock mass. The purpose of this paper is to study deformations and re-fracture characteristics of surrounding rock mass in deep underground engineering. First, deformations and cracking characteristics of intact rock samples are analyzed on the basis of uniaxial and triaxial experiments. The lateral constraint testing method is then applied to study deformation and re-fracturing characteristics of cracked rock mass. The lateral constraint test provides different lateral stiffness to the cracked rock samples and causes different failure modes in the cracked rock samples. Conditions for re-fracturing have been derived and validated through the lateral constraint tests, which can be used to study load capacities and stabilities of surrounding rock in deep underground engineering under structural constraints formed by different supports.