Theoretical and Numerical Investigations of Blasting Influence Range of Advanced Consolidation Grouted Rock Mass on an Underground Tunnel

The strong blasting disturbance causes weak and broken surrounding rock damage, which is a key problem in underground engineering. Advanced consolidation grouting can strengthen the original rock and help the safety control after blasting. The advanced consolidation grouted rock mass near the excavated profile is selected as the research object and the influence of blasting on the grouted rock mass is analyzed using both theoretical and numerical approaches. First, an analytical model to calculate the safe vibration velocity (SVV) is established based on the theory of multiple reflection and transmission effects of a strong stress wave and the strain rate effect of the rock strength. Then the blasting influence range is investigated by comparing the SVV of grouted rock and peak particle velocity caused by the perimeter and main borehole, respectively. Finally, the numerical calculation model of the weak and fractured rock mass is simulated by UDEC to verify the rationality of the theoretical results. Theoretical results indicate that the blasting of perimeter boreholes results in a larger influence range on the grouted rock near the contour profile. The blasting influence range of grouted rock mass is approximately 1.47-3.00 m outside the designed profile. Numerical results show that the damage range was reduced by approximately 26%-64% compared to nongrouted rock. Advanced consolidation grouting can significantly improve the blasting explosion resistance of weak and broken rock mass. Additionally, the research results can provide certain guidance for blasting and excavation design of the weak and broken surrounding rock, which has important theoretical significance and engineering application value.