Tunnel boring machine (TBM) should face high rockburst risk directly in deep-buried tunnel in hard rock. Real-time microseismic monitoring on rockburst risk analysis is carried out duringTBM construction in the #3 diversion tunnel of Jinping II Hydropower Station. The correlation between rockburst and microseismic activity is researched. The results show that:
The spatial distribution of rockburst and microseismic activity has a good correlation with each other that both are characterized with regional concentration and all moderate and strong rockburst occurred in areas of concentrated microseismic activity.
It is better to analyze rockburst risk based on multiple seismic parameters.
Comprehensive parameter seismic Schmidt number can be well used for rockburst risk analysis in deep-buried tunnel with TBM excavation.
Therefore, microseismic activity spatial distribution, multiple seismic parameters and seismic Schmidt number can be used together for rockburst risk analysis in deep-buried tunnel with TBM excavation.
Rockburst has become more and more prominent under high in-situ stress in deep-buried projects. It causes serious casualties and economic losses and has become a major hazard in the field of industrial safety. Jinping II Hydropower Station is located on the Yalong River, Sichuan Province in Southwestern China. The long tunnel system of Jinping II consists of seven parallel tunnels with an average length of 16.7 km including four diversion tunnels, two assistant tunnels and one drainage tunnel. The long tunnel system is generally at a depth of 1,500 to 2,000m with a maximum depth of about 2,525m (Shan et al. 2010). It is a typical example of a deep-buried project. Tunnel boring machine (TBM) has been used in the project because it is efficient. However, TBM may face high rockburst risk directly in the deep-buried tunnel in hard rock. Several strong and extremely strong rockburst have occurred in the drainage tunnel with TBM excavation and caused serious casualties and economic losses (Chen et al. 2011). Therefore, microseismic monitoring technique has been used in some deep-buried diversion tunnels withTBMexcavation in order to real-time monitor and forecast rockburst risk.