隧道洞口受力分析及进洞方案探讨

当前隧道施工倡导"零刷坡"进洞理念,洞口仰坡尽量避免大挖大刷,在减少施工工作量和难度的同时,较好地保护环境。用库仑理论对洞口受力进行分析,并以此为依据确定进洞采用大管棚还是小导管。洞口地段的施作关键点在于限制初期支护的变形,同时应控制掌子面、仰拱、二衬间的安全步距,及早封闭成环,仰拱和衬砌紧跟。

Analysis of Tunnel Entrance Force and Discussion on Entrance Scheme

Currently,“zero slope”is advocated in tunnel construction to avoid the excessive excavation and large slope cutting;thus,reduce the workload and difficulty in construction as well as protect environment as far as possible.This pa-per analyzes the force of tunnel entrance by the theory of Coulomb,and determines whether the entrance scheme should adopt large pipe shed or small duct.The key of portal bracing lies in the limitation of initial support deformation,mean-while,attention should be promptly given to the control of safety distance among tunnel face,inverted arch,and secondary lining and timely closing of loop,inverted arch and lining.