Effect of moving train load on ground movement and tunnel deformation due to stacked shield tunnelling

Stacked tunnel constructions adjacent to operating metro lines are frequently encountered in dense underground space, leading to undesired settlement and existing tunnel deformation. In this paper, ground movement and tunnel deformation were studied due to stacked shield tunnelling using field monitoring and numerical simulation, particularly the effect of adjacent moving train load on ground and tunnel responses was mainly investigated. Numerical model was implemented based one engineering project of the stacked shield tunnel in Tianjin, China. The results indicate that the ground vertical deformation is influenced by the position of new tunnel and existing tunnel, while the ground horizontal deformation occurs specifically at the top of the new tunnel. The train load contributes to an increase in both vertical and horizontal deformations of the ground and an intensified longitudinal settlement deformation in the existing tunnel. A ground settlement prediction was proposed that considers the stiffness of the existing tunnel and effect of train load. This study provides an in-depth investigation into the deformation of ground and existing tunnel and addressed the non-negligible effect of adjacent train load when evaluating safety of stacked shield tunnelling.