ROCKBURST MONITORING AND DYNAMIC PREVENTION OF ENLARGING EXCAVATION IN DEEP UNDERGROUND LABORATORY

There was intensive rockburst risk during the excavation of China Jinping Underground Laboratory(CJPL-Ⅱ)expansion project. Therefore,we established an optimization layout method of fixed microsesmic(MS)sensor array for adjacent short tunnels with same excavation direction,as well as dynamic MS sensor array for opposite expansion excavation at one-side. Meanwhile,we proposed an optimization principle of rockburst warning frequency based on the degree of rockburst risk. The rockburst control measures corresponding to CJPL-II enlarging excavation is given too. The real-time monitoring,dynamic warning and prevention on rockbursts during CJPL-II anisotropic excavation is realized based on these proposed methods. The rockburst warning is in good agreement with the actual situation and the CJPL-II enlarging excavation project is successfully completed. We analyzed the difference of temporal and spatial evolution laws of MS activity between each CJPL-II enlarging excavation segments. The results show that the MS activity of the new tunnel is more active than that of the expansion excavation section,and the rockburst risk is also higher. The size of excavation section,depth of excavation and structural plane affect the degree and spatial characteristics of MS activity during enlarging excavation. This study can provide reference for the safety construction of similar deep projects.