Rock Burst and Instability Analysis for Coal Roadways Based on Unified Strength Theory

Based on the unified strength theory (UST), a model of rock burst and instability was established in this paper, with which the effects of intermediate principal stress (IPS) and coal seam strength parameters (cohesion and inner friction angle) on the distribution characteristics of vertical stress on coal roadway as well as plastic zone width was discussed. This model is compared with models based on Mohr-Coulomb criterion and Drucker-Prager criterion respectively. Accordingly, the features of the said effects was obtained. The results show that the unified solution in terms of UST is of widespread theoretical significance in that it collects a series of ordered pairs as solutions;in comparison, the solution for rock burst and instability using Mohr-Coulomb criterion is partially conservative, while the Druker-Prager criterion counterpart is too dangerous;the change of IPS and inner friction angle leads to markedly varying evaluation results of rock burst and instability. The key to reasonable assessment on rock burst and instability lies in a full consideration of the effects of IPS and coal seam strength parameters (cohesion and inner friction angle).