Deformation rule and mechanical characteristics of temporary support in soil tunnel constructed by sequential excavation method

Abstract

The temporary support of tunnel constructed through sequential excavation method is considered one key point because of its large deformation and complex force. The in-situ deformation of temporary support was monitored in two soil tunnels. Results show that the temporary support presents “convergence–expansion–stability” regularity in the horizontal direction and “settlement–uplift–stability” regularity in the vertical direction. Finite element numerical simulation method was used to obtain the displacement and stress of the temporary support based on the stratum geological parameters at tunnel site. Compared with the field test results, the numerical simulation values have differences, but the deformation rules are consistent. The temporary support bear not only axial force, but also the frequently variable bending moments and shear force. Combined the results of field test and numerical simulation, we proposed that the longitudinal connection reinforcement between each steel frame and steel fabric should be set in the temporary support. Alternatively, steel fiber-reinforced shotcrete could be used in the temporary support when necessary.