Dynamic Responses of a Tunnel Embedded in a Saturated Half‐Space Under Variable‐Speed Loads Based on Green's Function Method

ABSTRACT This paper develops a semi‐analytical solution for predicting the dynamic response of a tunnel embedded in a saturated half‐space under moving loads with variable speeds. The tunnel is modeled as an infinitely long cylindrical shell, while the surrounding ground is represented as a saturated poroelastic half‐space. The load with non‐uniform velocity is formulated using the Dirac delta function. By employing the Fourier transform and potential decomposition, Green's function for the tunnel–ground system is derived. Dynamic responses of the system under variable‐velocity and horizontal loading are obtained through the convolution of the load function with Green's function. Our results demonstrate that load acceleration significantly affects the amplitude of both displacements and pore pressure, causing substantial amplification or attenuation. Horizontal loading considerably alters the distribution and magnitude of horizontal displacement. Both the critical velocity of vertical displacement and its corresponding peak value are influenced by load acceleration. Softer soils and deeper soil layers exhibit more pronounced sensitivity to load acceleration in terms of vertical displacement.