The effect of surface structures on soil deformations due to tunnelling in sand

In urban tunnelling projects, surface buildings interact with tunnelling-induced ground movements. Understanding this interaction aids when predicting the behaviour of buildings above tunnelling works. However, much uncertainty still exists about the impact of structures on tunnelling subsidence and thus current design practice is widely based on empirical methods that neglect this soil-structure interaction. To refine current modelling assumptions and reduce uncertainty, more detailed knowledge of the influence of buildings on tunnelling-induced ground displacements is needed. This paper presents results from an experimental investigation that seeks to provide a more thorough understanding of this soil-structure interaction problem using more realistic surface structures. In particular, it focuses on the effect of surface structures on the ground surface and subsurface soil displacements. Three centrifuge tests with building models placed in different regions of the tunnelling-induced settlement trough were compared to a greenfield case. The ground model consisted of a dense, dry sand and the building was 3D printed. Results showed how the structure alters the vertical and horizontal soil displacements associated with tunnel excavation. Soil deformation mechanisms were notably influenced by the position of the building model relative to the tunnel, causing different magnitudes of vertical and horizontal ground movements above and next to the tunnel, widening of the surface and subsurface settlement troughs and localised failure beneath building corners.