PREDICTION OF ROCKBURST AT WALL ROCKS OF TUNNELS IN SOUTHWEST

The prediction of rockburst is a great challenge for the construction of underground engineering. We take a tunnel in southwest China as a case study. We consider the three conditions inducing rockburst as：rockburst occurring probability of rock mass, the integrity of rock mass and the high in-situ stress. We take the maximum stored elastic strain energy(Es) and the rock brittleness modulus(B) as the indicators. We then analyze the rockburst occurring probability of quartz sandstone and limestone in the deep tunnel. Based on the collected in-situ stress data we collected, with the assistance of finite element method which immediately simulates the geological process, we launch a back analysis on the stress field of the rock mass in the tunnel area and consequently obtain the high in-situ stress-section in the area. Utilizing field sampling tests, we study the physical and mechanical properties of the wall rocks like the uniaxial compressive strength of intact rock. We summarize the previous rockburst predicting methods, employ the comprehensive engineering geological analysis, elaborate the conditions causing tunnel rockburst. Then, we use the theory of rock mass mechanics, the non-linear science as guidance, the geological comprehensive analysis method and the stress intensity ratio method to predict the location and intensity of rockburst that may occur in the tunnel area.