Unsymmetrical Loading Evolution Law and Surrounding Rock Control for tunnels with Extremely High Geostress and Layered Surrounding Rock
(1. School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031; 2. Sichuan Highway Planning, Survey, Design and Research Institute Ltd., Chengdu 610095; 3. China Railway Fourth Survey and Design Institute Group Co., Ltd., Wuhan 430063)
Abstract：
Taking the gently inclined layered surrounding rock of the Grand Canyon Tunnel as the case, and adopt? ing the 3DEC discrete element analysis method and combining with the means of field monitoring, the evolution law of the surrounding rock unsymmetrical loading under the high geostress and different dip angles of rock stratum is deeply studied, the relationship between the unsymmetrical loading and the field support structure damage is revealed, and the optimal support parameters are proposed according to the influence of the bolt support parameters on the unsymmetrical loading control. The research shows that the deformation and failure of the support structure under the condition of high geostress and gently inclined rock stratum show obvious asymmetry. With the increase of the dip angle of rock stratum, the peak position of the maximum principal stress of the initial support shifts from the crown to the right shoulder, and the bending deformation of the anti-dip side is greater than the sliding deformation of the down dip side. With the increase of bolt length, the shear slip zone of surrounding rock, the initial support displacement and the maximum principal stress of the initial support gradually decrease. The optimal length of the bolt is about 3.5~4.5 m, the bolt is set along the vertical direction of bedding plane, and the unsymmetrical loading of the initial support structure is significantly improved. After the field optimization of support, the left and right shoulders are symmetrically deformed, the displacement is basically identical, and the unsymmetrical loading is significantly improved.
PU Song1 XIANG Long2 LIAO Hang1 YU Tao1 YAO Zhigang1 FANG Yong1 ZHU Muyuan1
.Unsymmetrical Loading Evolution Law and Surrounding Rock Control for tunnels with Extremely High Geostress and Layered Surrounding Rock[J] MODERN TUNNELLING TECHNOLOGY, 2023,V60(1): 90-99
2023, Vol. 60 