Application and Optimization of the Parameters of the High-Level Boreholes in Lateral High Drainage Roadway

Abstract

The key parameters of high-level boreholes in high drainage roadways affect the gas treatment effect of the working face directly. Therefore, the layout parameters of high-level boreholes in the lateral high drainage roadway (LHDR) are determined and optimized as necessary. Based on the LHDR layout on the 2-603 working face of the Liyazhuang coal mine, the key technological requirements on high-level borehole parameters were analyzed and the distribution characteristics of the gas volume fraction in the coal roof were studied. The gas migration law in the mined-out areas was obtained and the layout locations of high-level boreholes were determined finally. The research demonstrates that the high-level boreholes lag the 2-603 working face distance and the position of the final borehole (the position of the final borehole in this paper refers to the distance between the final borehole and the roof) influence the stability of boreholes and the gas extraction effect. The distribution of the gas volume fraction from the intake airway to the return airway can be divided into the stable stage, slow growth stage, and fast growth stage. Influenced by the flow field in the mined-out areas, the mean volume fraction of the borehole-extracted gas has no obvious relationship with the gas volume fraction at the upper corner. According to the final optimization, the high-level borehole is determined as having a 15 m lag behind the working face and the position of the final borehole is 44 m away from the coal seam roof. These have been applied successfully in engineering practice.

Study and Application of High-Level Directional Extraction Borehole Based on Mining Fracture Evolution Law of Overburden Strata

“…Former research has shown that a rock drainage roadway and high-level directional extraction borehole can effectively extract gas in the fissure zone and have great operational stability in the upper corner of the goaf and return air flow [10][11][12][13]. However, the rock drainage roadway has the disadvantage of requiring a large amount of site construction, long operation cycles, and high costs [14][15][16]. With improved equipment, the high-level directional extraction borehole can replace the high-level drainage roadway to extract gas in the goaf and fissure cycles, and high costs [14][15][16].…”

“…However, the rock drainage roadway has the disadvantage of requiring a large amount of site construction, long operation cycles, and high costs [14][15][16]. With improved equipment, the high-level directional extraction borehole can replace the high-level drainage roadway to extract gas in the goaf and fissure cycles, and high costs [14][15][16]. With improved equipment, the high-level directional extraction borehole can replace the high-level drainage roadway to extract gas in the goaf and fissure zone, which can shorten the construction period, save construction costs, and improve the efficiency of gas control [17][18][19].…”