Analysis of influencing factors of roadway surrounding rock plastic zone based on Drafcker-Prager criterion

The expansion of plastic zone in surrounding rock is the fundamental cause of frequent roadway accidents.Based on DP criterion, the boundary equation of plastic zone in surrounding rock under non-uniform field is derived, equivalent radius is converted for non-circular section roadway, plastic zone morphology under different lateral pressure coefficients is analyzed, and the influencing factors of plastic zone under different DP criterion are analyzed by single factor method.The results show that when the lateral pressure coefficient is in the range of 0.6-1.5, the plastic zone is elliptic.When the lateral pressure coefficient is less than 0.6 or more than 1.5, the plastic zone presents a butterfly distribution.Roadway pressure and surrounding rock lithology significantly affect the shape and scope of the plastic zone.Reasonable selection of roadway location according to the actual engineering can effectively reduce the difficulty and cost of roadway support.The influence of intermediate principal stress on the plastic zone of roadway surrounding rock has strong interval.Roadway support can improve the cohesive force and internal friction angle of rock mass through grouting, and then reduce the plastic zone, but the effect is limited.The radius of plastic zone decreases linearly with the increase of supporting resistance.The plastic zone radius calculated by different DP criterion is different.Reasonable application of DP yield criterion can not only ensure the safety of coal production, but also reduce the cost of engineering.