Numerical modelling of ground-borne vibration from a metro tunnel embedded in saturated soil strata using a 2.5D fully-coupled formulation

Abstract

Although many metro tunnels are constructed in soil strata that are already saturated, the efficient and accurate modelling of ground-borne vibration from a metro tunnel embedded in saturated soil strata is still limited. Within this framework, this paper presents a 2.5D(two-and-a-half-dimensional) numerical model to calculate the ground-borne vibration from a metro tunnel embedded in saturated soil strata, which well represents the fully-coupled train-track-tunnel-soil system and takes the effect of groundwater into account. In this model, the soil mediums beneath the ground water table are modelled by fully saturated poroelastic mediums governed by Biot's theory, while the other soil mediums and the tunnel structure are modelled by single-phase elastic mediums governed by viscoelastic dynamics theory. In the meanwhile, the metro track is modelled as infinitely long Euler beams connecting the tunnel base structure through the distributed spring-damper elements representing the fasteners, and the train composed of several vehicles is modelled by multiple rigid bodies connected by spring and damping systems. The governing equations of the track-tunnel-soil system are first formulated in the framework of a 2.5D approach, and the moving train is then subsequently coupled to it to provide a dynamic response solution of the coupled train-track-tunnel-soil system. The proposed model is thoroughly validated by comparing its simulated results with the corresponding field measurements. Additionally, the importance of accounting for the liquid phase's impact on metro-train induced environmental vibration in saturated soil regions is clearly shown.