Dynamic Analysis of Tunnel Structures and Surrounding Granular Soils under Cyclic Loads of a Vibrating Machine

This paper concerns the seismic behavior of shield circular tunnels and surrounding granular soils subjected to cyclic loading of a vibrating machine foundation. A 2D dynamic finite element model was established by using the PLAXIS numerical software. Then, the internal forces and deformations produced in the tunnel lining segments and the upper soil layer settlements and stresses were investigated under both static and dynamic conditions. Moreover, in order to investigate the influence of surrounding soil and concrete lining characteristics, a parametric study was carried out on the essential parameters including the soil stiffness and cohesion as well as the damping parameters and the concrete lining thickness. It has been shown that the ground surface settlements and the peak point of the tunnel deformations decrease with the increase of the soil stiffness. It is also shown that amplifying the soil material cohesion and damping leads to the decrease of induced deformations and internal forces of the concrete lining segments. Furthermore, an increase of the concrete lining thickness will decrease the settlement of the upper soil mass and the tunnel lining deformation, whereas it will increase the magnitude of internal forces of the lining elements.