Study on causes of string hole in gas extraction cross seam under disturbance of hydraulic reaming

doi:10.16265/j.cnki.issn1003-3033.2019.11.026

Abstract

Abstract: In order to improve gas drainage efficiency in coal mine by solving the problem of excessive pressure relief of hydraulic reaming and determining reasonable coal expansion amount, firstly, causes of string hole after reaming were revealed and clarified with Hoek-Brown principle. Secondly, fluid structure coupling mathematical model was constructed, and changes of stress and permeability of coal body under porous conditions after reaming and pressure relief were simulated and analyzed through COMSOL simulation software. Finally, occurrence of string-hole under different coal expanding amount was investigated based on field reaming tests. The results show that as coal-expanding quantity increases, radial displacement and deformation of coal near the hole will also increase. And probability of string-hole will grow sharply as permeability of coal around enlarged holes improves greatly when pressure relief is sufficient. It is found that field test results are basically consistent with that of theoretical analysis and simulation, which can provide some reference for implementation of hydraulic reaming technology in mines under similar geological conditions.

Key words: hydraulic reaming, string hole, radial displacement, reasonable coal expansion, coal permeability

CLC Number:

X948

WANG Junming, LIU Qing, BAO Kun. Study on causes of string hole in gas extraction cross seam under disturbance of hydraulic reaming[J]. China Safety Science Journal, 2019, 29(11): 164-170.

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