Train-Induced Vibrations from a Tunnel in a Layered Half-Space with Varied Groundwater Table

This paper presents an analytical method to analyze the effect of the variation in the groundwater table on train-induced vibrations from subway tunnels. The soil above the groundwater table is considered as a dry single-phase medium, while the soil under the groundwater table is simulated as a saturated porous medium. The solution for wave propagation in a multilayered half-space is derived by using the transfer matrix method. By using the wave transformation, the multilayered soil is subsequently coupled with the tunnel via boundary conditions at their interface. The train-induced vibrations are computed by coupling the proposed tunnel–soil model with the vehicle–track model. The numerical results demonstrate that the displacement field tends to that of a saturated half-space when the groundwater table is above the tunnel, while it tends to that of a dry single-phase half-space as the groundwater table is under the tunnel. The vibration levels increase as the groundwater table drops. Furthermore, the effect of the variation in the groundwater table becomes more significant as the soil permeability decreases.