Abstract:

The feasibility of bench method to shallowburied asymmetricallypressured tunnel of superlarge crosssection is studied by taking Shiyanling Tunnel on Menghua Railway for example. Firstly, the threebench excavation method to temporary invert and vertical support pillar is selected by comparing bench method to traditional partial excavation method; and the structure stability is analyzed by software MIDAS so as to guide the tunnel construction. And then, the problems encountered during construction, i.e. large settlement of crown top, fissures of primary support and the ground and the influence of blasting on tunnel deformation in hardsoft heterogeneous ground are analyzed; and relevant countermeasures are adopted. The site application results show that the abovementioned method with advantages of easy operation and high efficiency is feasible to Shiyanling Tunnel. The study results can provide reference for similar projects in the future.

Key words: Menghua Railway, superlarge crosssection tunnel, shallowburied and asymmetrical pressure, bench method