Horizontal mechanical responses of single pile due to urban tunnelling in multi-layered soils

This paper presents a theoretical method for the horizontal mechanical responses of single pile due to tunnelling in multi-layered soils. Based on the homogenization theory and the integral L&P formula, ground horizontal displacements due to tunnelling in layered soils can be solved analytically. The pile-soil interaction model is established in which the pile is assumed to be an Euler-Bernoulli beam placed on the Pasternak foundation. According to the two-stage thought, the horizontal displacements and bending moments of the pile can be evaluated quantitatively if the calculated horizontal displacements are input into the interaction model. The proposed method is verified by comparing with the numerical method, field measurement and centrifugal test. Parametric analyses are also performed to investigate the influence of the parameters of the pile and excavation, especially the soil stratification on the mechanical responses of the pile. Results found that the GAP parameter, the distance of tunnel axis from pile axis, the length, the diameter and the elastic modulus of the pile all have an important influence on the horizontal displacements and bending moments of the pile. Importantly, the soil stratification has a non-negligible influence on the mechanical responses of the pile. The stiff interlayer sandwiched between the upper and lower soil layer can significantly limit the horizontal displacements of the pile but increase the bending moments.