Abstract: The tunnel excavation sequence has important impacts on the deformation of the surrounding rock mass and the later supporting procedure. This is especially true for the rock mass classified as IV and V. However, the analogy and insitu survey are the major ways to determine the excavation sequence and the optimized excavation sequence is not usually selected. The three dimensional numerical analysis using FLAC3D is performed on the Dawangou Tunnel excavation which different sequences can be simulated and the deformation of the surrounding rock mass, development of the plastic zones and the stress within the rock mass can be compared so that an optimized excavation can be determined.

Key words: Tunnel Engineering, Excavation Sequences, Numerical Analysis, FLAC^3D