Pile-tunnel interaction: a conceptual analysis

The underground space of densely populated cities contains parts of buildings, utility installations, deep foundations and tunnels. It is possible that new tunnels will be built within close proximity of existing pile foundations. Therefore pile tunnel interaction (PTI) must be assessed so that it is possible to ensure safety for both the tunnel construction and the pile-supported structures. This paper presents a simple model to evaluate the pile settlements and increment of axial force due to tunnel excavation. The displacement field around the tunnel can be used to estimate the pile displacement and the differential displacements around the pile-soil interface. Based on an example plane strain calculation of an unlined tunnel, different possible pile locations were evaluated. The results were compared to six studies from the literature and considerable agreement was obtained for the trends of ratios of pile to surface settlement and increment of axial stress on the pile