Occurrence mechanisms and judging criterion on circular tunnel butterfly rock burst in homogeneous medium

Starting from the mechanical mechanism of the formation,development and explosive destruction of the plas- tic failure zone in the surrounding rock of the circular tunnel under the homogeneous condition,the occurrence mecha- nism of rock burst in the tunnel is revealed. In a certain stress and surrounding rock environment,due to the induction of the triggering event,the stress field of the roadway will be suddenly changed,and the butterfly-shaped plastic zone in the ground will expand sharply and jumpily,then a huge amount of elastic energy which is gathered in the body of coal or in the system of surrounding rock will be suddenly released in the form of vibration,sound and coal or rock mass burst. The occurrence condition of rock burst is explained by the theory of butterfly rock burst in the tunnel. Be- sides,the three butterfly rock burst criterions are given,which provides a new idea for the forecasting,prediction and prevention of rock burst.