REAL-TIME MICROSEISMIC MONITORING AND ITS CHARACTERISTIC ANALYSIS DURING TBM TUNNELING IN DEEP-BURIED TUNNEL
(1. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China；2. Ertan Hydropower Development Co.，Ltd.，Chengdu，Sichuan 610051，China；3. Beijing Vibroflotation Engineering Co.，Ltd.，Beijing 100024，China)
Abstract：According to the difficulties and shortcomings of real-time microseismic monitoring during tunnel boring machine(TBM) tunneling with overburden of over 2 000 m-thick hard and brittle rock mass，the traditional microseismic monitoring technology，used in the mines，is optimized and improved；and the new microseismic monitoring technology is utilized during the TBM tunneling in the diversion tunnel #3 of Jinping II hydropower station. The monitoring results show as follows：(1) The ambient noise is much and complex，but the main characteristic is clear during TBM tunneling；and it can be filtered through the proposed filtering method effectively. (2) There is an obvious relationship that microseismic activity increases with the increase in TBM tunneling rate between microseismic activity of surrounding rock mass and the TBM tunneling rate，vice versa. Microseismic activity is very weak during the period of TBM maintenance，but it becomes most active when TBM working lasts for 4–6 hours after TBM maintenance. (3) Before some rockburst occurred，distribution of microseismic events and energy release gradually convert from discrete to relatively concentrative in spatial domain，the number of microseismic events and the radiated energy increase rapidly in temporal domain；and apparent volume of surrounding rock mass has a sudden increasing trend；energy index has a sudden drop trend in the same time. (4) When microseismic monitoring is carried out during TBM tunneling covered with thickly hard and brittle rock mass，effective microseismic information can be acquired；the evolution characteristic and law of microseismic activity can be found and known；and more accurate early-warning information of rockburst can be provided. Therefore，it is possible and feasible to forecast the occurrence of rockburst by microseismic monitoring.
2011, Vol. 30 
