Study on precision plugging technology and equipment for secondary grouting in failed single-channel boreholes

Zhang Pan; Pan Bojie; Qin Jinhui; Hao Fuchang; Gao Baobin

doi:10.16186/j.cnki.1673-9787.2023120061

Abstract：Objectives To address the problems of severe air leakage and low gas extraction concentration in failed boreholes,a study was carried out on precision plugging technology and equipment for secondary grouting in single-channel failed boreholes.Methods An accurate detection device for locating borehole air leakage was developed.The specific leakage position was identified by measuring the gas extraction concen-tration at different positions along the pipe bottom.Based on this,precision plugging technology and equip-ment for secondary grouting at the pipe bottom of failed boreholes were designed.A total of 23 low-concentration failed boreholes in the 2-803 working face of Liyazhuang Coal Mine were treated using this technology.Results The developed equipment achieved a secondary grouting pressure of up to 2.0 MPa with good plugging performance.The sealing-section length and depth can be freely adjusted,and the entire de-vice is fully retrievable,making the process simple,efficient,and convenient for field application.Accord-ing to the differences in gas extraction concentration,the main leakage channel of the 2-803 working face was determined to be located 17～23 m from the borehole collar.After applying the technology,the average gas extraction concentration increased from 29.01%before grouting to 81.35%,80.47%and 70.66%after one day,one week,and one month,corresponding to increases of 1.8,1.77 and 1.44 times,respectively.The average pure gas extraction rate increased from 0.05m3/min to 0.161,0.158,and 0.141 m³/min,repre-senting increases of 2.2,2.16 and 1.82 times,respectively.Conclusions The proposed technology and equipment can achieve precision plugging of low-concentration failed boreholes,reduce gas control costs,and improve the effectiveness of gas extraction and management.