This paper aims to develop a relatively simple approach to examining the interaction among multiple foundation systems for closely spaced high-rise structures, termed here "urban forests", and to assess the extent to which this interaction can influence the foundation performance of a building within this "forest". To simplify the analysis and avoid undue numerical complexity, each foundation system is modelled as an equivalent pier, representing the deep foundations, the connecting mat or raft, and the soil contained within the piled raft system. The behaviour of a single equivalent pier is considered first, with the surrounding foundations being represented by an axisymmetric smeared ring outside the pier. After examining some general behavioural characteristics, a simplified approach using the concept of interaction factors is developed to facilitate estimation of settlement interaction between multiple adjacent foundations. The accuracy of this simplified approach is assessed via comparison with the axisymmetric approach. The significance of the interaction among foundations is examined for some simple cases. It is found that the settlement interaction depends largely on the characteristics of the foundations surrounding the building being examined. When all buildings are supported on foundations extending to a relatively stiff layer, the interaction effects tend to be relatively small. However, if one or more of the buildings is founded on a relatively short foundation system, interaction effects may be more significant. An example is provided to illustrate the application of the approach.
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