Stability of a Roadway below a Coal Seam under Dynamic Pressure: A Case Study of the 11123 Floor Gas Drainage Roadway of a Mine in Huainan, China

Abstract

Coal and gas outburst is an important risk faced by coal seam mining in the Huainan region of China. In order to control gas outburst, the gas is predrained by digging a floor gas drainage roadway. To study deformation due to dynamic pressure, the failure characteristics of the floor, and their effect on the stability of the floor gas drainage roadway, a comprehensive monitoring method combining Brillouin optical time-domain reflectometry- (BOTDR-) distributed fiber optics and self-potential exploration was adopted. Dynamic data monitoring of the rock strata between the 11123 working face floor and the floor gas drainage roadway of a mine in Huainan was carried out. The field data obtained showed that, when stabilized by rock bolts and other fixed components in the surrounding rock mass of the floor gas drainage roadway, under the influence of mining, the area of concentrated stress appeared at a depth of 20.7 m, when cracks eventually formed, but the overall structural stability of the surrounding rock mass remained good. The stress distribution and crack evolution of the bottom plate under the influence of dynamic pressure showed spatiotemporal characteristics. Of these, the effect of the lead support stress was 107.48 m, and the range of effect of the hysteresis stress was 34.42 m. When the working face mining position arrives and is far from the monitoring station, the failure depth of floor rock stratum shows the following rule: unchanged in the early stage, deepened continuously in the middle stage, and finally remained stable. It takes about eight days for the dynamic adjustment of this process to finally stabilize. The results of this study can provide guidance for devising suitable procedures for carrying out intelligent green safety mining and for warning about the hazards of roadway damage.