The Effectiveness Study Of Adjacent Foundation Excavation To Underground Shield Tunnels

With the rapid development of economic and social and urban modernization, ground space cannot meet people’s travel needs. Metro appears largely solved this problem people encounter. But with the subway construction, ground engineering in the construction process will face some difficulties, such as the adjacent soil excavation of the subway tunnel. Soil excavation cause changes of stress and deformation of the surrounding soil, which will lead changes of stress and deformation of shield tunnel lining.In this paper, research on this issue, using the finite element software ABAQUS and based on various factors, the paper study the influence of subjacent tunnel induced by excavation. This paper compared the result of simplified calculation method and the simulation results. The main contents of this paper are listed as follows:(1)The paper studies soil stress-strain behavior, calculates the parameters of Mohr-Coulomb model and NHRI constitutive model using the automated triaxial apparatus and experimental material is silt in Zhengzhou.(2) This paper simplified segments using the "Stiffness reduction method" on the subway tunnel. According to the simplified segments, this paper simulates the influence of excavation on the adjacent shield tunnel using the finite element software ABAQUS. This paper considers the tunnel depth, the depth of excavation, the horizontal distance between the axis of tunnel and excavation and difference of two and three dimensional modeling. This paper analyses stress of tunnel, the tunnel horizontal displacement, shear stress of tunnel and the ridge of excavation bottom.(3)This paper calculates the additional stress of the tunnels axis using “comer point method”, and then calculates the deformation of the tunnels axis using the Winkler elastic foundation beam model.(4)This paper calculates the deformation of bottom of foundation pit using the "residual stress method".