Microseismic characteristic analysis in deep TBM construction tunnels
TANG Zhili1, LIU Xiaoli1, LI Chaoyi2, QIN Pengxiang2, XU Qianjun1
1. State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China; 2. Huaneng Tibet Brahmaputra Hydropower Development Investment Co., Ltd., Chengdu 610200, China
Abstract:The increasing depth of underground construction tunnels has led to instabilities of the surrounding rock caused by the excavation unloading is the rock structures. A real-time microseismic monitoring system was built to monitor and evaluate the stability of the rock during excavation foe a tunnel in Tibet, China. The system measured the temporal and spatial evolution of the microseismic activities during tunnel boring machine (TBM) excavation. The results were used to relate the b-values of the microseismic events and the stability risks of the surrounding rock. The results show that the number of microseismic events and the energy released increase with increasing TBM activity. A large number of microseismic events are concentrated in space and time before collapse of the rock mass and the gathering area coincides with the position of the rock mass collapse. The b-value is an important index to evaluate the surrounding rock stability. The results verify the feasibility of microseismic monitoring to evaluate the stability of the surrounding rock and a reference for microseismic monitoring in similar projects.
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