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In this paper, a novel numerical methodology to deal with longitudinally invariant soil-structure interaction problems is proposed. The methodology uses the finite element method to model the structure and the singular boundary method to model the wave propagation in the soil, both formulated in the wavenumberfrequency domain. The versatility presented by the finite element method combined with the simplicity and computational efficiency of the singular boundary method results in a friendly, robust and accurate novel methodology to address the soil-structure interaction problems. The accuracy of the proposed method is assessed by comparing it against 2.5D FEM-MFS and 2.5D FEM-BEM approaches for two cases: a thin cylindrical shell and a star-like beam structure, both embedded in a full-space medium. Moreover, the computational efficiency of the proposed method is evaluated against 2.5D FEM-MFS and 2.5D FEM-BEM methods. In the final step, the applicability of the proposed method is studied through an example of a railway tunnel embedded in a layered half-space. The results presented in this work exhibit the advantages of the novel approach in modelling simplicity, numerical efficiency and robustness with respect to previous methodologies.

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A floating ladder track is established in the present paper as a next-generation non-ballasted track system. The three-dimensional model consists of a track (mass-spring-damping system) and the underlying soil. Rectangular pulse loading with an amplitude of 60 kN is considered as the wheel loading system. A time domain coupled finite element with a semi-infinite absorbing boundary condition is employed using FEM software. Due to axial symmetry of the model instead of the track axle, only half of the model is simulated. It is observed that the performance of the floating ladder track is better in mitigating measured vibration than that of the traditional ballasted track. Numerical results of the floating ladder track reveal that the increase of damping and stiffness yields more vibration responses, which is a straight nonlinear relationship. Although increasing density of the protective layer decreases vibrations on the ground, it has no effect on structural components of the track except for the protective layer. Furthermore, this kind of track is more effective at a closer distance to the source of vibrations.