Numerical study the effect of the ratio of distance between the center the central axis of the tunnel and center of structures to tunnel’s diameter parameter on the interaction of the tunnel-surface structures, Case Study- Niayesh Tunnel, Tehran

Abstract

Population growth in most cities increases the need for building surface and subsurface infrastructures. Tunneling causes the deformation of the surface and subsurface structures. Also the structures have effects on ground movements that caused by tunneling influence. Therefore, evaluating the interaction between tunnels and surface structures, which have the effect of surface structure on the rate of settlement and horizontal displacement that caused by tunneling is so crucial. In recent decades, researchers have conducted studies that focus on a variety of factors and in recent years, some researchers have examined the impact of geometric parameters separately on the interaction tunnels and surface structures. However, due to the influence of the geometric parameters on each other’s, Evaluation of combinations of these parameters with regard to the impact of each one’s to others seems necessary. In this paper, the influence of distance between the center the central axis of the tunnel and center of structures to tunnel’s diameter parameter on the settlement and horizontal displacement curves that cause by tunneling investigated. Therefore the numerical finite element method (FEM) has been used. Based on numerical modeling results, with decreasing of this ratio, the amount of settlement is reduced. It is also observed that by reducing of this the inflection point of the settlement curve’s, from a distance of 38 meters is reduced to 28 meters distance from the tunnel axis, which means reducing the impacted area of the settlement. The variations of this parameter, has no impact on the longitudinal settlement curves above the central axis of the tunnel, this is due to the distance from the central axis of the tunnel structures. With decrease in this ratio, in the center of the structure, the maximum of longitudinal settlement increased; so that the maximum amount of longitudinal settlement with a ratio of 1.45 is 3.5 mm that with the reduction in the this ratio to 0.84, the maximum amount of longitudinal settlement increased to 8 mm. Also with decreases in this ratio, the amount of horizontal displacement increased.