Study on the stability and control of coal pillars in water-bearing gas extraction boreholes

Narrow-coal-pillar entryprotection can effectively increase the recovery rate of coal resources and improve the relationship between mining and replacement. However, there are problems in construction and maintenance, especially under the condition of water accumulation in goaf and high gas content in mine, it is important to the stability of coal pillar. Based on the engineering background of goaf side entry driving in 30108 working face of Shiquan Coal Mine, a quantitative characterization method of borehole crack based on MATLAB image processing was proposed in combination with the visual detection technology of drillings. On the basis of mechanical model and numerical simulation of immersed coal pillar, the reasonable width of coal pillar was determined, the drainage scheme of goaf and the high-strength asymmetric support scheme of roadway "anchor cable net beam+reinforcement of narrow coal pillar side cable beam+reinforcement of narrow coal pillar side grouting" were proposed and the industrial practice was carried out. The research results show that the proportion of fracture area in the borehole section decreases in negative logarithm with the increase of borehole depth. When the coal pillar width is 10.00 m, there is a large range of elastic zones in the coal pillar in the normal section and the gas drainage drilling section, which has a strong bearing capacity. The roadway control effect has remarkable control effect and significant economic benefits.