Temporal-spatial evolution of acoustic emission during progressive fracture processes around tunnel triggered by blast-induced disturbances under uniaxial and biaxial compression

Under high stress conditions in deep underground engineering projects, frequent and strong blast-induced disturbances can easily lead to spalling and collapse of the surrounding rock around tunnels, even generating dynamic hazards such as rockburst. Herein, the acoustic emission (AE) technique was adopted to monitor the occurrence of progressive fracture process around tunnels under static stress and dynamic disturbance. The results showed that the macroscopic cracks around the circular opening occurred due to the combined action of the external loading and blast-induced disturbances. The spatial distribution of AE events directly reflected the damage evolution inside the specimens, and the areas of concentration of AE event were found to be consistent with the locations of the macroscopic fractures. This study provides an insight for the depth and range of the failure zone around the tunnel. The failure area and morphology around the tunnel are closely related to the external stress and blasting disturbance. The dynamic disturbance can deepen the damage degree and accelerate the failure speed of the tunnel. The power-law characteristics of AE signals after blasts can be used to evaluate the time required for rock mass to return to a stable state, and apparent stress is a meaningful measure to judge the stress level in rock mass.