Abstract:

Based on the Boussinesq solution and Mindlin solution and considering the combined effect of soil and structure, a semianalytical prediction method for the deformation of subjacent metro tunnel caused by foundation pit excavation in undulant soil and rock strata is proposed. A prediction formula considering the burial depth of the bedrock surface is proposed by comprehensive parameter analysis. In order to ensure the safety of the tunnel during the construction, the tunnel deformation is monitored throughout the construction process by using combination scheme of artificial measurement and automatic measurement. By analyzing the predicted theoretical values and measured data, the accuracy of the proposed formula is verified and the influence of foundation pit excavation on tunnel deformation is further investigated. The results show that: (1) The proposed empirical prediction formula can accurately predict the maximum uplift of the tunnel under different buried depths of bedrock surface. (2) Compared with the maximum uplift deformation of the left line tunnel in stronglyweathered rock and moderatelyweathered rock, the maximum uplift deformation of the right line tunnel in fully weathered rock and residual soil increases by about 40%. (3) Tunnel uplift deformation in weathered rock area is 1/5-1/4 of that in soft soil area.

Key words: undulant soil and rock strata, metro tunnel, uplift deformation, excavation unloading, semianalytic prediction method