Abstract: In the procedure of shield construction， the inappropriate controlling of support pressure on the tunnel face may cause risk of accident， such as the nearby pipeline rupture and the incline of existing buildings. The influence of different buried depth ratio (C/D)， internal friction angle on the instability mode of excavation face and the limit minimum support pressure was investigated on the basis of the Flac^3D numerical model and limit equilibrium model. According to the comparison between the two different analysis methods， there is obvious difference between the support pressure predicted by the limit equilibrium model and the actual support pressure， which is caused by the fact that the limit equilibrium model cannot reflect the procedure that the coefficient of lateral pressure changes with the displacement of tunnel face and dynamic depth change. The research may provide great theoretical evidence to the engineering practice in the solid stratum.

Key words: tunnel face stability, buried depth ratio, limit support pressure, Flac^3D, limit equilibrium method