Failure determination method regarding local outburst prevention measures for coal and gas outburst

Discharge holes is the primary measure concerning local outburst prevention, however, in recent years, there have been numerous instances of accidents in which outburst still occurred, after drilling outburst prevention holes and taking local outburst prevention measures. The reason lies in the fact that those measures haven’t realized their expected goals and are in a state of failure. How to determine the effectiveness of measures to prevent accidents is a crucial link. Therefore, in view of this situation, taking the core elements of outburst as the focus point, namely in-situ stress, the failure determination method concerning localized measures preventing coal and gas outburst in excavation working face was proposed and applied. The primary conclusions were as follows: based on the stress distribution characteristics of the working face, a failure determination method regarding local outburst prevention measures was proposed. It was divided into two aspects: firstly, measures taken didn’t pay attention to avoid the destruction of coal in the fracture area, resulting in the reduction of its strength and thus inducing a disaster; secondly, the gas and stress in the stress-concentration area, were ineffectively unloaded, which led to breaking the original equilibrium state and promoting the occurrence of outburst. According to the concept of stress-softening and dilatancy of coal mass, the stresses, strains, and widths in the three areas, namely fracture area, plastic area, and elastic area, in front of the working face were recalculated. Meanwhile, a quantitative form regarding the failure criterion mechanism was defined in relation to its content. According to the technical requirements of local outburst prevention measures, the optimal drilling length for advanced drilling, loose blasting, and hydraulic loosing was regulated by using the failure determination method. Depending on the failure criterion, typical drilling failure types were listed as well as the failure mechanism was qualitatively and quantitatively described. The research can help to reasonably arrange and optimize the localized measures in the excavation face, enhance the effectiveness regarding outburst prevention measures.