关键词: 全风化花岗斑岩  浅埋 三台阶+临时仰拱开挖法； , 壁导坑法 变形控制

Abstract:

The exit portal section of Xiangshan tunnel is located in fully weathered granitic porphyry ground, for which "minibench + ring cut" tunneling method is adopted at the primary stage. However, serious deformation occurs during the tunnel construction. On basis of analysis on the deformation, the author summarizes the key points for the tunneling in such ground, optimizes the construction scheme and recommends single side drift tunneling method and "three benches + temporary invert" tunneling method. The guiding principle of "pipe roof reinforcement, strict grouting, short excavation cycle length, strong support, early closing of the reinforcement structure ring and constant measurement" is followed in tunneling. Owing to the strengthened reinforcement, increased temporary support, early closing of the reinforcement structure ring and immediate secondary lining, the deformation of the tunnel is brought under effective control.

Key words: completely weathered granitic porphyry; , shallow cover "three benches + temporary invert", tunneling method, single side drift tunneling method deformation control