New method for introducing gradient stress into rock-burst prediction

During the excavation of underground projects, the tangential stress in the surrounding rock near the cave wall is distributed in a gradient because of the disturbance of excavation unloading in the deep rock mass. In order to explore the effects of gradient stress on rock-burst characteristics, the rock-burst tests under the effects of different gradient stresses on large-sized specimens are conducted with the help of the independently developed rock-burst test simulation device. It is found that there is an obvious correlation between the intensity of rock-burst of rock mass and the gradient stress that it is subjected to. On the basis of considering a large number of engineering examples, the intensity ratio of gradient stress is introduced to optimize the intensity stress ratio criterion so as to establish a prediction method for rock-burst with gradient stress. The results show that there is a clear correlation between the intensity of rock-burst of rock mass and the gradient stress it is subjected to. The criterion considering the gradient stress of the rock-burst overcomes the uneven problem of the traditional intensity-stress ratio index, and the prediction accuracy is raised to 90.4%, which provides a theoretical basis for the prediction of rock-burst of underground projects.