Zhonghecun tunnel design for dual three lane tunnel, single tunnel width 5m,height 16.5m, left, right tunnel is 12M, in the process of excavation using 3 step excavation, overlying rock is weathered mudstone to sandstone, rock cover thickness is about 12M, the integrity and stability of rock mass difference. In the process of hole digging, the parallel construction, construction caused the deformation and failure surface, cracks between left and right images tunnel rock wall produced a parallel to the tunnel axis direction, in order to ensure the smooth excavation tunnel. Need to step on tunnel around the amplitude distance optimization. The three-dimensional finite element of three kinds of different construction step away from the stress and displacement of numerical simulation, the simulation results show that: with the increasing construction step, the surface deformation and decreases linearly, the construction step distance of 0, 10, 20 and 30m, the crown settlement are 90mm 30mm, 50mm, and 27mm. When the construction step is larger than 20m, less influence of construction of adjacent tunnel. Through on-site adjustment, determine the construction step distance is 20m, the height is within 30mm, which can ensure the safety of the tunnel construction, the mechanical parameters of rock mass are determined by comprehensive, three-dimensional finite element for the tunnel excavation step numerical simulation to optimize the tunnel construction step, and this method is effective and feasible.
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