Rockburst prediction and analysis of activity characteristics within surrounding rock based on microseismic monitoring and numerical simulation

Abstract

The access tunnel in the main powerhouse of the Shuangjiangkou hydropower station is located in an area with high in-situ stress and complex geological conditions in Southwest China. Strain-structure rockbursts occurred frequently and posed serious threats to the safety of personnel and equipment during the tunnel excavation. The maximum depth of the rockburst failure reached 1.8 m at the left sidewall of the tunnel. A three-dimensional microseismic (MS) monitoring technology was introduced to monitor microcracks within the tunnel surrounding rock in real time. Using Matlab software to write a program, the main frequency values of MS signals were extracted. Based on MS monitoring, some source parameters were obtained. Three parameters, including apparent stress, apparent volume and main frequency value, were used to analyze the activity state within the surrounding rock. This method had a high time resolution and can guide the on-site construction in real time. The combination of the three parameters can better characterize different damage characteristics of the surrounding rock in real time. When the apparent stress of some events was relatively high, the apparent volume of some events was relatively large and the main frequency values of some events were relatively low, the risk of rockbursts was relatively high. Finally, a 3D numerical simulation software (RFPA3D) was used for a numerical calculation to explore strain-structure rockburst mechanisms. An area where the rockburst risk was relatively high and rockburst prediction was relatively difficult was delineated, and this paper provided a new idea for predicting the stronger strain-structure rockbursts. Understanding of activity state within surrounding rock is very important for controlling rockburst occurrence or weakening rockburst strength. The research results have significant value for safe and efficient construction on site.