A FE-IBE method for linearized nonlinear soil-tunnel interaction in water-saturated, poroelastic half-space: II. A revisit to two widely used analytical solutions

Abstract

For circular tunnels, two widely used analytical solutions are well suitable for seismic design, given that they provide simple formulas for conveniently estimating the internal force and the deformation of the tunnel. The assessment of the applicability of these analytical solutions has been an issue of interest. The companion paper (Part I) provides a 2-D finite element-indirect boundary element (FE-IBE) coupling method for seismic analysis of tunnels in water-saturated, poroelastic half-space with soil nonlinearity. This coupling method has been proved to be accurate and efficient for addressing problems involving dynamic soil-tunnel interaction. This paper (Part II) uses the results obtained by the coupling method as benchmark to evaluate the applicability of two widely used analytical solutions for seismic design of tunnels with soil nonlinearity. The comparison between the analytical solutions and the coupling method is performed within a wide range of flexibility ratios. Besides, different seismic loading intensities as well as tunnel buried depths are also considered. The purpose of this paper is not to conduct validation of the analytical solutions, but rather to investigate the effect of the dynamic soil-tunnel interaction, which the analytical solutions cannot account for, thus to further recognize the limitations of the analytical solutions. Moreover, for tunnels in water-saturated soils, emphasis is on the effect of interaction between solid frame and pore water, which has not been investigated in previous related studies. The result shows that the analytical solutions considerably underestimate the lining internal force and the lining deformation of the tunnel, which may lead to unsafe design of underground tunnels. The difference between the analytical solutions and the coupling method in this paper may exceed 50%, highlighting the significance of more realistic and rigorous simulation of the soil-tunnel interaction, especially for a water-saturated soils scenario.