A technology to extract coal mine gas using thin sub-layer mining with hydraulic jet

摘要

A high-pressure water jet can cut a slit in the coal seam to relieve the stress and improve the permeability, which makes coal mine gas be extracted more easily. Currently, the inner diameter of the nozzle and the flow of present high-pressure water jet for the cutting technology are small, which causes small cutting depth and width and a low efficiency of permeability improvement. To solve this problem, a new water jet technology with large flow was studied. By this technology a thin sub-layer of a coal seam can be mined effectively to relieve the stress and improve the permeability. This technology was tested in the Zhao Zhuang coal mine, the test parameters were determined, the test results were analysed, and it was found that after mining the thin sub-layer, the pressure of the coal seam reduced sufficiently and its permeability was significantly improved.