Abstract:In order to improve the stability evaluation system of tunnel face,considering the effects of declined ground and tunneling footage,the upper bound expression of supporting force for three-dimensional shallow tunnel face was derived and the optimal upper bound solution of supporting force was obtained by further using the planning procedure.The results show that the ratio of supporting force of tunnel face to soil cohesion is linearly affected by the dimensionless parameter γD/c(γ is soil bulk density,D is tunnel section diameter,c is soil cohesion),ratio of tunnel footage to tunnel depth,and ratio of ground overload to soil cohesion,whereas it is nonlinearly affected by the ratio of tunnel depth to tunnel section diameter,inclined ground surface angle,and internal friction angle. The internal friction angle,inclined ground surface angle,ratio of tunnel depth to tunnel section diameter,and ratio of tunneling footage to tunnel depth have a significant effect on the passive failure mode,while the dimensionless parameter γD/c and ratio of ground overload to soil cohesion have less effect on it.