3D Behaviour of Buildings due to Tunnel Induced Ground Movement

Abstract

Ground subsidence from tunnel excavation below existing buildings may result in building distortion and develop structural damage. Previous case histories have shown that buildings may deform three-dimensionally when the tunnel alignment is orientated to the building facade. The authors incorporated a three-dimensional distortion parameter called twist into damage assessment by extending the current beam model to three dimensions. In this study, the new method is reviewed, and the concepts of the local and global twists are discussed. Results of a 3D Finite Element (FE) parametric study of global and local twist deformations of buildings due to tunnel-induced ground movement are compared in temporary and permanent cases during and after the construction of the tunnel. To investigate the behaviour of a twisted building, varying building stiffness, building geometry, and orientation angle are considered in the analyses. Comparison of the global and local twist shows that the global twist is not always the maximum twist during or after excavation of the tunnel. However, because of the temporary nature of the local twist, the global twist is still considered more critical than the local twist in terms of damage to the building. A new modification factor for the twist for different building stiffness factor is being proposed in the form of design graph. The design graph is included in the current three-stage procedure for assessing potential building damage. The modified procedure is used to predict the performance of a case study building affected by tunnel construction.