Theoretical study and application of energy extreme value discrimination method of softening zone for bursting hazard

Considering the current situation that it's difficult to quantify the discrimination of rockburst hazard, an analytical solution for the softening zone energy of surrounding rock under rockburst in a circular roadway is obtained theoretically based on the elastoplastic softening model of a circular roadway. The critical softening zone energy, critical softening zone radius, critical roadway shrinkage displacement, and critical roadway shrinkage rate are determined. An energy extreme value discrimination method of softening zone for bursting hazard is proposed. The critical softening zone energy is taken as the evaluation basis of the bursting liability of the coal seam where the roadway (a full coal roadway) is located. The uniform energy index, which is the ratio of the external disturbance energy of the surrounding rock softening zone to the critical softening zone energy, is used as the evaluation basis for bursting hazards. Theoretical analysis shows that the smaller the critical softening zone energy of the roadway surrounding rock is, the stronger the bursting liability of the coal seam is, and the greater the uniform bursting hazard index is, the stronger the bursting hazard of the roadway. Subsequently, based on the critical softening zone energy and the uniform energy index, a classification standard of bursting liability and an evaluation method of bursting hazard are proposed. The reliability of the softening zone energy extremum criterion, the bursting liability classification standard, and the bursting hazard evaluation method was verified through indoor and field tests. The energy extreme value discrimination method of softening zone for bursting hazard considers the internal and external factors of roadway rockburst comprehensively and can judge the rockburst risk through field real-time observation, which is a more scientific and reasonable method to predict the risk of roadway rockburst. The research work has important theoretical guiding significance for the prevention and control of roadway rockbursts.