Experimental and numerical studies on the shear mechanical behavior of rock joints under normal vibration loads

Abstract

Jointed rock masses of roadways in underground coal mines are heavily disturbed by rock-cutting vibrations from Tunnel Boring Machines (TBMs), posing significant challenges in controlling the deformation and damage of the surrounding rock. To investigate the mechanical behavior of rock joints under normal vibration loads, a series of laboratory vibration experiments were conducted with varying frequencies and amplitudes, based on in-situ vibration characteristics during TBM rock-cutting. Subsequently, the relative damage coefficient Dv and relative shear strength ratio Rτ were proposed to quantify the damage degree of rock joints. The findings revealed a non-linear growth of rock joints damage with increasing vibration frequency and amplitude. The vibration frequency and amplitude are categorized into three and two stages, respectively, depending on the damage of rock joints. Additionally, the vibration failure mechanism of rock joints was elucidated using the discrete element method. It was observed that the failure of weakly joints is controlled by both the “filler-rock” interfaces and “filler-filler”, while strongly joints fail solely due to the “filler-rock” interfaces, confirming the agreement with laboratory experiments. Moreover, effective grouting reinforcement was proven to significantly enhance the vibration resistance of in-situ jointed rock masses, preventing vibration collapse resulting from TBM tunneling disturbance.