Twist deformation of buildings from ground movements due to skewed-tunnel excavation

Abstract

Substantial ground settlements from tunnel excavation near existing buildings may result in building distortion and increase the risk of structural damage. Current studies on building-tunnel interaction are usually limited to the plane-strain analyses that neglect the out-of-plane deformation behaviour of a structure. When tunnels are orientated (skewed) to the building, additional three-dimensional deformation such as out-of-plane ground movements and building twist may lead to further building straining. Estimation of the twist is not always straightforward as the building stiffness modifies the greenfield displacements induced by tunnelling. In this paper, the results of a three-dimensional numerical parametric study on the influence of existing surface structure on the twist deformation are presented. The buildings are represented by elastic shell elements where their in-plane geometries, stiffnesses, and rotation angles with respect to the tunnel axis are varied. The results show that in most of the cases, presence of the building reduce the global twist deformation in comparison to those of greenfield condition, except in the case of low building stiffness, and when the tunnel is excavated with skew angle less than 30° relative to the existing buildings.