An effect evaluation method of coal seam hydraulic flushing by EMR

Present coal seams in China are characterized by great gas pressure and content, low permeability features, and thus, the extraction of gas is difficult and gas disaster remains serious. To improve the permeability of coal seam, the hydraulic flushing is adopted, so the effect evaluation of stree relief and permeability enhancement will be necessary before gas extraction. In this paper, an electromagnetic radiation (EMR) experiment system of coal seam hydraulic flushing was established, and the EMR characteristics of coal during hydraulic flushing were studied. The EMR test of hydraulic flushing was carried out in the Liangbei coal mine, China, and the gas extraction flow and coal stress were measured simultaneously. And then, the variation laws of EMR and the effect evaluation of hydraulic flushing were analyzed. The results showed that coal deformation and fracture produced abundant EMR signals during hydraulic flushing. The variation of the EMR signals was synchronous with the variation of load, and the large the load variation was, the greater the EMR intensity and count were. Compared with before hydraulic flushing, the EMR signals changed significantly after hydraulic flushing, and the variation amplitude of the EMR intensity was consistent with the variation amplitude of the coal stress and gas extraction flow. So the EMR method achieved the objective of effect evaluation. It's feasible and dependable to evaluate the effect of coal seam hydraulic flushing by EMR.