Three-dimensional numerical analysis of the interaction of two crossing tunnels in soft clay

Abstract

Recently, with the development of underground construction, multi-tunnel engineering has become a matter of concern since the interaction between tunnels at close ranges could cause additional deformation in strata as well as surrounding structures and even serious damage to surface buildings. These tunnel displacement and soil deformation problems can be effectively predicted using numerical methods considering the influence of various factors, such as the anisotropic nature of soft clay. To this end, the anisotropic elastoplastic constitutive S-CLAY1 is implemented in finite element code to investigate deformation problems in the strata and nearby structures caused by the excavation of multi-tunnels. This paper focuses in particular on configurations of two crossing tunnels. Multiple 3D numerical simulations using ABAQUS enable successive analyses conducted for tunnels at different spacings (1.5D, 2.5D, 3.5D and 4.5D, where D is the tunnel diameter) of configurations aligned vertically. The results, including the ground settlement, lining force and moment, and tunnel convergence, are analyzed. For each aspect, the most unfavorable case is determined by comparing the results of different simulations. This investigation can provide a reference for multi-tunnels design and construction. Keywords: Multi-tunnels, Anisotropy, Clay, Ground loss, Finite element, Constitutive relation