Stability Analysis During the Construction of Large Cross-section Tunnel Through Contact Belt

Abstract

Instability of surrounding rock and supporting crack, large deformation phenomenon frequently happens in period of the construction process of large cross-section tunnel through contact belt. Taking Malin tunnel project of Lanhai expressway through unconformable contact belt as background, impact of tunnel span and vertical distance between tunnel and contact belt on tunnel stability was analyzed by numerical simulation method. The results indicates that tunnel plastic zone and that of contact belt are more prone to link together with larger tunnel span at certain distance of tunnel and supporting structure safety would suddenly reduce; The zone affected by contact belt is divided into secondary section and primary section according to variations of tunnel stability, and special research work on tunnel design and construction scheme should be carried out in primary section. The results could provide basis and reference for the similar engineering design and construction.