Experimental and numerical studies on mechanical behavior of pre-stressed infilled rock joints subjected to horizontal vibration loading

Underground jointed rock masses are usually subjected to a coupled effect of static pre-stress and vibration disturbance from rock-cutting in Tunnel Boring Machines (TBMs) tunneling. To investigate the mechanical behavior of pre-stressed infilled rock joints disturbed by horizontal vibration loading, a series of laboratory and numerical experiments were conducted, based on the in-situ vibration characteristics during TBM rock-cutting. The P-wave velocity and direct shear test techniques are combined to quantitatively characterize the damage of infilled rock joints. The experimental results reveal that the damage degree of rock joints exhibits a nonlinear increase with the increase of vibration frequency and amplitude, and the decrease of static pre-stress. Low static pre-stress (below 0.5 MPa), high vibration frequency (above 70 Hz) and high vibration amplitude (above 0.3 mm/s) are adverse factors to the stability of rock joints. From the PFC 2D simulation, the contact force chain and contact force field were analyzed to elucidate the failure mechanism of infilled rock joints. The failure mode of infilled rock joints is closely related to the level of parameters, consisting with the results in laboratory experiments. In addition, the comparison of vibration results for weakly and strongly filling material demonstrates that grouting reinforcement enhanced the vibration resistance of in-situ jointed rock masses.