An H-M contact model to simulate soil-structure interactions under tension in offshore environments

Abstract

An efficient soil-structure interaction interface is developed in this paper as a gap that can be filled with water to model the whole process of structure separation from soil (i.e. losing effective mechanical contact with suction sustained). This hydro-mechanical interface is formulated as node-to-face contact, using lubrication theory to describe the gap water motion, while both the structure and the soil are generalised as porous media obeying mass and momentum balances. Continuities of water pressure, flux, and stresses are enforced at the boundaries between the structure, gap, and soil. Incremental forms of governing equations are derived to accommodate material nonlinearity, and finite element formulations are detailed. The interface is validated by three examples. The first two consider a two-layer soil subjected to compression and tension, respectively, with the interface embedded in the middle. The numerical results agree well with the derived analytical solutions using Laplace transform. The third example models lifting a square footing off Modified Cam-Clay seabed at varying rates. Numerical results agree well with available centrifuge data.