Numerical study on the lateral soil arching effect and associated tunnel responses behind braced excavation in clayey ground

Abstract

This study uses numerical simulation to investigate the soil arching effect behind a braced excavation in clayey ground and derive an insight into the mechanisms behind the nearby tunnel responses. The numerical results are validated by field measurements of a well-documented case history. It is found that the lateral excavation-induced loosened zone is located behind the position with maximum wall deformation. The arching zone develops above the loosened zone and the stable zone is formed at the peripheral. Ground stress is transferred from the loosened zone to the adjoining stable zone and arching zone. The stress transfer along the arching zone drags the soil against the bracing and increases the lateral earth pressure around the upper part of the wall, where the soil is in passive stress state. The stress transfer along the shear plane increases the lateral earth pressure within the stable zone, where the soil is also in a passive state. The stress transfer induced by the minor principal stress arching in the loosened zone increases the radial load on the tunnel crown for the tunnel located entirely in the loosened zone. In addition, the tunnel deformation and bending moment associated with the arching effect are discussed.