Abstract:After the construction of the tunnel begins, the problems caused by the bias will become very passive and may lead to the major safety accidents. Generally speaking, when there is a mountain bias at the tunnel entrance, the mountain should be measured in detail before its excavation, and the necessary technical measures should be taken. Relying on the Huitougou Tunnel Project, three constructing conditions of before slope cutting, slope cutting by 5° and slope cutting by 10° are analyzed. The method of FLAC3D numerical simulation is used to analyze the influences of the different slope cutting angles on the topographic bias tunnel. The slope cutting can reduce the buried depth of the tunnel and decrease the slope angle so as to reduce the adverse effects of bias on the tunnel.