Investigation of sudden faults instability induced by coal mining

Abstract

Study on the mechanism of coal burst induced by faults instability is a major concern for the safety mining and efficient production in the underground coal mine. In this paper, the sharp change of roof bolt loading, roof separation, roadway deformation and mining face support stress were observed during the routine field tests. According to the preliminary estimation, the reason for such a phenomenon was possibly relevant to the sudden instability of fault structures. To investigate the sudden faults instability, a physical test was carried out with two fault structures. The modelling results suggest that the strain rate from relatively low to sudden changes may be identified as a precursor of fault slip. The overlying strata was severely collapsed under the interactive effect of two faults. The depth of collapsed strata between two faults was higher than that influenced by a single fault. The difference between the first-stage and the second-stage coal mining is studied in three aspects: the area of fault influenced zone, characteristics of stress distribution near fault and the degree of fault slip. Due to the severely collapsed strata between two faults, the abrupt stress change could be induced during excavation of coal mining face, and thus, more attention should be paid to the influence of overlying strata movement above goaf between two faults. The sudden collapse of roof strata and abrupt stress change could release tremendous strain energy and induce coal bursts.