Abstract:

No.2 ventilation shaft of Qinling highway tunnel is one of the largest ventilation shafts in the highway tunnel field at home and abroad. Rock burst is a serious problem during the shaft excavation according to the analysis of in-situ engineering geological data. For evaluating rock burst tendency from the perspective of lithological character, the uniaxial compression deformation test and physical model test are carried out. There is a high tendency of rock burst in surrounding rock by analyzing the modified brittleness index and model test result, so it is essential to strengthen rock burst prediction and control. The initial stress field of surrounding rocks of shaft is regressively analyzed by 3D finite element method according to in-situ measured data by hydro-fracturing and distribution properties of in-situ stress. Then the comprehensive rock burst prediction and analysis based on Russenes and Tao criteria are made according to the induced stress field obtained by Kirsch solutions and in-situ stress distribution of surrounding rock of shaft respectively. The result shows that the weak and moderate rock burst will occur during shaft excavation. Finally, some countermeasures to rock burst are proposed. It provides valuable references for other projects.

Key words: tunnel engineering, ventilation shaft, rock burst prediction, in-situ stress, finite element method