COMPREHENSIVE JUDGMENT METHOD OF ROCK STABILITY SURROUNDING DRILLING AND BLASTING TUNNEL WITH MICROSEISMIC MONITORING

This paper aims to comprehensively interpret and judge the stable state or disaster of the surrounding rock of the tunnel constructed by deep-buried drilling and blasting method. First of all,we propose the methods of microseismic event classification and surrounding rock damage grade classification based on the source parameter space. Second,we construct a time series of multiple microseismic parameters. The comparison reveals the microseismic characteristics of the three states of surrounding rock stability,collapse and rockburst during blasting construction. Finally,we propose a comprehensive judgment method for the stability of the surrounding rock in the construction of deep-buried tunnels by drilling and blasting. This method is suitable for the judgment of the stable state of surrounding rock,landslides and rockburst disasters during the blasting construction of deep-buried tunnels. On this basis,we combine with geological conditions to determine the disaster risk level. The research results show that the three states of surrounding rock (i.e. stability,collapse and rockburst) during the construction of the drilling and blasting method have unique characteristics and laws in the source parameter space and the microseismic time series trend. In the stable stage of surrounding rock,a strong stress adjustment occurs only in a short time after blasting. In the abnormal stage of surrounding rock stability,the microseismic event continues to be active for a long time after blasting,and the cumulative energy,cumulative event number,and cumulative apparent volume curve increase rapidly,and the energy index curve declines rapidly. The research results can provide an important reference for the surrounding rock stability judgment,disaster early warning and prevention and control scheme of deep-buried tunnel constructed by drilling and blasting method,as well as for other similar projects.