Influences of soil characteristics on longitudinal deformation of shield tunnels induced by surface surcharge

With the development of urbanization in China, it is common to find the surface surcharge in a large scale around the metro tunnels, which will seriously threaten the safety of the lining structures and their service capability. To obtain the additional stress on the axis of shield tunnels caused by the surface surcharge, the Boussinesq’s solution is widely adopted, whereas it cannot be applied in multi-layered soils. In this study, firstly, the additional stress in multi-layered soils is obtained by using the Fourier integral transformation. Secondly, the existing tunnel is regarded as the Timoshenko beam, and the displacements and internal forces exerted on the shield tunnel are obtained based on the two-stage method. From the proposed method, it can be found that the underlying layer has larger influences on the settlement of shield tunnels than those by the overlying soils.