A study of the characteristics and influence mechanism of time delayed rockburst in a TBM tunnel under the blasting disturbance

The occurrence of time delayed rockburst usually has strong randomness and will pose a great threat to construction safety. Excavation disturbance and blasting disturbance will have impact of varying degrees on the potential time delayed rockburst area. It is of great significance to carry out studies of the characteristics and mechanism of time delayed rockburst in a TBM tunnel under the blasting disturbance. Based on a TBM headrace tunnel, five time delayed rockburst occurred in K54+000—K54+700 section during demolition tunnel blasting excavation are studied by using theoretical analysis and comparative analysis method. The results show that (1) strong and medium rockburst areas are located near gentle dip faults. Short and small concealed joints and fine joints with filling are developed in surrounding rocks. The slight rockburst is far from the fault or near the normal fault. Except for the fine joints with filling, at least one steep structural plane with filling tendency and dipping in SW direction is developed. (2) The time delayed rockburst of the TBM tunnel has longer delay blasting time and longer lag working face distance, and the disturbance effect of blasting on the TBM tunnel is relatively small. (3) Blasting disturbance makes it easy for the surrounding rock instability in the potential time delayed rockburst area, which accelerates the process of time delayed rockburst. The research results can provide a useful reference for the early warning and prevention of time delayed rockburst in TBM tunnels.