The Liangshui tunnel of Lan-Yu Railway is constructed with the complex geological condition of weak broken wall rock; and the tunnel depth changes greatly because of terrain fluctuation. Formulating appropriate construction scheme according to the special formation conditions in relevant sections is key issue for the safety control of the tunnel. Based on the investigation data

numerical simulations are conducted using the fast Lagrangian analysis of continua in 3 dimensions(FLAC3D) to research the influence of excavation length on surrounding rock deformation in different buried depth cases. Rules of the effect of buried depth on excavation circulation length are studied from the deformation angle; and the excavation circulation lengths most favorable to deformation control in different buried depth cases are analyzed; the results offer technical guidance and theoretical support for construction decision.