Deformation and mechanical model of temporary support sidewall in tunnel cutting partial section

Abstract

A large cross-section shallow tunnel excavated by center cross diagram method (CRD) was constructed on a site with weak surrounding rock. Crown settlement and horizontal convergence were extensively monitored to investigate the performance of a temporary support wall. Based on field observations, effects of zone excavation on the temporary support sidewall were analysed extensively. Influenced by earth pressure applied by a subsequently zone excavated, the deformation of the temporary support sidewall at upper bench successively undergoes convergence, expansion, convergence, expansion and stabilisation five stages; and the deformation at lower bench undergoes convergence, expansion and stabilisation three stages. Based on the deformation and restriction condition of the temporary support sidewall during tunnel excavation, a small curvature beam was used to simulate the stress and deformation change of the temporary support sidewall. Then, mechanical model of the temporary support sidewall under the surrounding rock horizontal pressure and the upper structure loads were suggested, respectively. The total deformation of the temporary support sidewall induced by zoned excavation can be determined by superposition the deformation caused by different loads.