Relationship between reactive soil movement and footing deflection: A coupled hydro-mechanical finite element modelling perspective

Supporting footings of lightweight buildings on reactive soils are susceptible to damage induced by the cyclic shrink-swell movement of the ground, causing extensive financial damage. Due to this issue and limitations of existing analytical methods, the main aim of this study is to investigate the interaction between shrink-swell soils and raft footings (i.e., stiffened rafts and waffle pod rafts), by performing parametric simulations using a simplified three-dimensional hydro-mechanical finite element model. The developed model considers the link between soil saturation, soil suction and volumetric soil strain. Stiffened rafts and waffle pod rafts were observed to interact differently with reactive soils. Stiffened rafts formed complex soil profiles induced by the obstruction of soil moisture flow provided by in-ground beams. This had a significant effect to changes in soil suction and formation of soil profiles in the covered ground. Waffle pod rafts performed better on swelling soils, while stiffened rafts were more robust on shrinking soils due to the additional support provided by the in-ground beams counteracting applied line loads. A developed improved design guideline based on the performed parametric simulations, considering the influence of geometry, suggests that raft footings require stiffer sections than a traditional method.