Abstract: Based on the Biot's theory of the two-phased poroelasticity medium, a coupled model for a saturated layered ground containing an open trench and track is developed, and the effect of the open trench on reducing the vibration generated by a moving train is investigated. Firstly, the whole model is decomposed into two substructures, which are the saturated ground containing open trench and the track. Then, the dynamic responses of the saturated ground induced by the moving line-distributed vertical loads are calculated by using the 2.5D indirect boundary element method (IBEM), and simultaneously the dynamic responses of the track under the moving train loads and distributed loads are solved. Finally, the layered ground and the track are assembled according to the equivalence between the deformation of the track and the vertical displacement of the layered ground on the center point of the track. The validity of the proposed method is confirmed by comparing its results with the published ones. Numerical calculations are performed by taking uniform saturated half-space and a single saturated layer resting on the saturated half-space as models, and the effects of the parameters of the ground and the trench are studied. The numerical results show that the isolation effect of the trench on the layered saturated ground is better than that on the uniform saturated ground. The isolation effect of the trench on the saturated ground is better than that on the corresponding elastic ground. In addition, The trench depth, the porosity of saturated layer and the stiffness ratio of bedrock to saturated layer have significant influences on the isolation effect of the trench.