Preliminary study on radon detection application under condition of mid-deep coal seam mining

Due to severe problems caused by rock mass failure in the underground coal mining, the mechanism and critical conditions of rock mass failure have attracted attentions from the field of rock mechanics. Based on the mining and geological conditions of 2507^# working face in Hengjian coal mine, Handan mining field, the correlation between radon concentration changes and mining-induced surface cracks evolution has been preliminarily studied under the conditions of mid-deep coal seam mining. The field test results show that the first weighting interval of 2507^# working face is about 45 m and periodic weighting average interval is about 15 m according to the radon measurement data. The results are ba- sically agree with the underground mine pressure observation results and have a corresponding relation with the surface deformation cracks, which has further validated the feasibility of radon detection application under the conditions of mid-deep coal seam mining. Based on those, the concept of anomaly coefficient of radon (k) has been put forward, and the critical value k (no less than 15%) has been determined for predicting the breakage of main roof in overburden of 2507^# working face. Finally, prospects of radon detection had been proposed, such as the comprehensive detection methods, factors affecting radon exhalation, migration mechanism fissured rock mass and error adjustment of radon detection.