Analysis of Mechanical Behaviors of the Small-spacing Tunnel in Squeezing Rock Masses
(1 China Academy of Railway Science, Beijing 100081; 2 China Railway Southwest Research Institute Co., Ltd., Chengdu 611731;3 China Railway First Survey and Design Institute Group Co., Ltd., Xi′an 710043; 4 China Railway 11 Bureau Group Co., Ltd., Wuhan430071)
Abstract：
For the small-spacing tunnel, tube group effect and stability of middle rock pillars are the main chal? lenges, especially in squeezing rocks, it will result in that cracks occur earlier in the first excavated tunnel tube and then cracks occur at the right tube while construction is taken on the left tube. Based on the Xinchengzi tunnel which is a typical case of large deformation at the bellmouth-shape exit section in squeezing rock mass, a construction method of stress release with advanced pilot tunnel was proposed, and the effect was verified by comparison of structure test results and numerical analysis. The results show that compared with the conventional three-bench method, the forces acting on lining structure significantly decrease by using advanced pilot tunnel method to release stress, so it is practical both in theory and practice for the small-spacing tunnels in squeezing rock mass to use advanced pilot tunnel to release stress.
2019, Vol. 56 