Abstract:

In the construction of the pedestrian underpass of underground excavation with shallow overburden，it is crucial to rationally delimit the size of digging length. If the size of digging length is too small, the construction time will be prolonged and temporary protection will increase. If the size is too large, the earth on the top of the tunnel will be unstable, even collapse. Based on Terzaghi’s loose medium theory, a calculating formula of digging length in homogeneous soil is proposed and applied to layered soil. Some valuable conclusions on the shallow underpass construction are proposed through the simulation of finite difference method of Qingchun underpass; and their comparisons are made.

Key words: underground excavation with shallow overburden, pedestrian underpass, digging length, loose medium theory