Abstract
The monitoring of rockburst is one of the worldwide problems in underground engineering and how to effectively predict and early warn the occurrence of rockburst disasters has become an urgent problem to be solved. In this article, the high rockburst occurrence section of the deep diversion tunnel of Jinping Hydropower Station on the yalong River is taken as the research object. Based on the microseismic monitoring technology and combined with the principle of seismology with qualitative analysis and quantitative calculation, the distribution law of “time, space, and intensity” of microseismic activity and the change law of source parameters time series are used as the precursor characteristics of rockburst early warning. Based on these, the internal relationship between the microseismic activity and the rockburst micro-fracture was studied. The monitoring results show that the rockburst occurred before has obvious micro-fracture precursors. The microseismic activity is a self-organizing process from spatial disordered dispersion to ordered concentration. The abnormal changes in source parameters such as density of microseismic events, seismic energy density, the cumulative volume, energy index, 3S index, and b values can be used as a warning identification of rockburst. Therefore, the multivariate early warning method for rockburst monitoring based on the comprehensive analysis of source parameters in the deep tunnel is proposed. The prediction accuracy of this method is up to 80.6%, and it can provide reference for the rockburst prediction, warning, and safe construction of such tunnel engineering.
Highlights
Rockburst is a dynamic phenomenon and ejection caused by the sudden release of elastic deformation and potential energy accumulated in underground engineering rock mass under excavation disturbance
The Jinping microseismic monitoring project adopts Canadian Engineering Solution Group (ESG) monitoring system, which is mainly composed of Paladin digital signal acquisition system, hyperion digital signal processing system, and acceleration sensor
The multiparameter early warning model for rockburst monitoring of deep-buried tunnels of Jinping II Hydropower Station is proposed by combining qualitative analysis with quantitative calculation (Figure 8)
Summary
Rockburst is a dynamic phenomenon and ejection caused by the sudden release of elastic deformation and potential energy accumulated in underground engineering rock mass under excavation disturbance. At the same time, Feng et al (2015) analyzed the occurrence mechanism and later dynamic support of rockburst in Jinping Tunnel by studying the law of microseismic activity, and carried out detailed research on the occurrence law, prediction, and early warning problems of rockburst. In this article, taking the section of deep-buried tunnel with high rockburst occurrence of Jinping Hydropower Station as the research object, the real-time monitoring and analysis of the surrounding rock microseismic activities in the area of high buried depth and high in-situ stress were carried out. Through the qualitative analysis and quantitative calculation, the multivariate early warning method for deep hard rock tunnel rockburst monitoring in the Jinping II Hydropower Station was proposed and verified It may provide some references for the excavation of tunnels and prediction of rockburst during construction
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