Viscoelastoplastic model for an integrated tunnel-track system in weak rock formations

Underground railway transportation systems offer a sustainable solution for space constraints, especially in urban areas, however, the construction of such systems embedded in weak rock presents significant challenges. This study introduces a novel computational approach to evaluate the dynamic response of integrated tunnel-track systems while considering the effect of moving trains. The effect of a moving train load is assessed for the tunnel inlay and the weak rock surrounding the tunnel. A viscoelastoplastic model, incorporating Hooke’s, Newton’s and St. Venant’s elements, is introduced to simulate complex interaction within the integrated tunnel-track system. The model utilises Hoek-Brown criteria for the rock mass surrounding the tunnel. Firstly, the dynamic effects of the moving train loads are assessed for the track and the tunnel inlay, and then the resulting stresses on the tunnel inlay are treated as internal support pressure to evaluate the response of the surrounding karstic rock. The model is validated against existing experimental and numerical investigations. This study provides a valuable computational tool for practising engineers to assess the long-term structural response of integrated tunnel-track systems constructed in challenging weak rock formations.