Research on the Nucleation Mechanism and Early Warning Method of Strain Rockburst in Deep-Buried Tunnel Based on Microseismic Monitoring

Abstract

AbstractIn order to discuss the nucleation mechanism of strain rockburst, this paper takes the rockburst section of deep diversion tunnel of Jinping Hydropower Project of Yalong River as the research object. Through the study of microseismic monitoring technology and the regularity of microseismic parameters, as well as combining the qualitative and quantitative analysis, the nucleation process and instability failure mechanism of strain rockburst were revealed, and the internal relationship between microseismic evolution law and rockburst process was explored. The monitoring results and analysis showed that the development process of strain rockburst under engineering disturbance can be divided into three stages: tensile crack initiation and development stage, macroscopic shear crack formation stage, and overall instability stage, respectively. The failure process was mainly that two macroscopic shear cracks caused by tensile failure were connected and developed to the tunnel wall and then formed a closed triangle region. The rock mass in this area appeared plate-like splitting, spalling, and wedge-shaped rock mass ejection at a certain initial velocity, which eventually lead to intense rockburst and overall instability failure. The results also showed that the rockburst failure process under engineering excavation was in good agreement with the traditional syllogism of rockburst. Meanwhile, based on the evolution characteristics of source parameters and statistical parameters, including microseismic energy, moment magnitude, cumulative apparent volume, energy index, and b value, the quantitative interpretation of the source parameter provided significant evidence and insight into characterization of strainbursts. In addition, these parameter fluctuation characteristics can be effectively used as the precursor information and early warning index of strain rockburst failure. The results of this study can provide reference for monitoring and early warning of rockburst in deep tunnel and taking effective prevention and support measures in time.