Abstract:

Numerical simulation is made for the threebench sevenstep excavation method and twobench fivestep excavation method adopted in the construction of Zhifang tunnel located in carbonaceous slate ground. The deformation of the tunnel and the stresses acting on the primary reinforcement structure and the secondary lining under the condition of the above two excavation methods are analyzed. The analysis indicates that twobench fivestep excavation method is superior to threebench sevenstep excavation method in aspect of deformation control; however, under the condition of twobench fivestep excavation method, the  axial forces of the steel ribs and the stresses on the primary shotcrete and the secondary lining at the arch lumbar and the side wall have increasing tendency, except the fact that the axial forces of the bolts reduce.

Key words: three bench seven step excavation method, two bench five step excavation method, carbonaceous slate, deformation control, numerical simulation