Blasting excavation induced damage of surrounding rock masses in deep-buried tunnels

Blasting excavation disturbance is an important influencing factor related to the initiation and the evolution of the surrounding rock damage zone in deep-buried tunnels. Based on the excavation of auxiliary tunnels in the Jinping II Hydropower Station, the effect of blasting excavation disturbance on the surrounding rock damage zone in deep-buried tunnels is studied by means of in-situ rock mass acoustic velocity detection and numerical simulation. The results of the field detections and the numerical analyses show that under the disturbance of blasting excavation, the tunnel surrounding rock Excavation Damage Zone (EDZ) is mainly caused by the in-situ stress redistribution of surrounding rocks after excavation unloading, and the blasting load and the transient unloading of excavation loads are also important factors for the development of the surrounding rock EDZ. The dynamic damage effect caused by the transient unloading of excavation load is more remarkable when the surrounding rock masses under a high in-situ stress.