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.
Highlights
In coal and gas outburst mining areas [1], such as those surrounding the city of Huainan, in north-central Anhui Province, China, it is often necessary to design suitable floor gas drainage roadways [2] in advance, at a certain depth below the working face, and to carry out safety work related to equipment system layouts, such as coal seam gas extraction and ventilation
If the floor gas drainage roadway is located in the affected area and the on-site support conditions are insufficient, this will inevitably lead to the instability of the surrounding rock and of the floor gas drainage roadway and even render the operation of the roadway equipment system unsafe [3,4,5]
We chose to study and determine the characteristics of floor failure under the influence of dynamic pressure and the effect on the stability of the rock surrounding the floor gas drainage roadway. e results obtained in this study will be of great practical importance
Summary
In coal and gas outburst mining areas [1], such as those surrounding the city of Huainan, in north-central Anhui Province, China, it is often necessary to design suitable floor gas drainage roadways [2] in advance, at a certain depth below the working face, and to carry out safety work related to equipment system layouts, such as coal seam gas extraction and ventilation. E failure characteristics of the 11123 working face floor were determined, and the stability of the rock surrounding the 11123 floor gas drainage roadway under the influence of dynamic pressure was studied. E results obtained by comprehensive monitoring data are self-verifying, which improves the reliability of the data; (2) the response characteristics of the multiphysical field data and the changes in the stability of the surrounding rock under dynamic pressure were obtained, which will aid future studies on the stability of the rock surrounding a roadway; (3) it was found that the failure depth of floor strata lags behind the secondary deepening of the coal wall under the action of mining. Some scholars [29,30,31,32] in China have introduced this technology underground to study the deformation and damage of the roof and the surrounding rock in the mining process, and the test accuracy and data volume are better than the conventional testing methods
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