Coupled hydro-mechanical interfaces to enable uplift modelling in offshore engineering

In many fields of geotechnical engineering, the numerical modelling of structure-soil interaction remains a fundamental but challenging topic. A key problem is the requirement of a versatile interface to account for the contributions from both the soil skeleton and the pore fluid between the contacting structure and soil. This is especially relevant for modelling uplift problems, where separation occurs and a gap is eventually formed, with suction sustained in the short term and dissipated gradually. Both the effective stresses of the soil skeleton and the pore fluid pressures must be modelled properly, including flow within the developing gap. There is a demand for coupled hydro-mechanical interfaces that address the mechanical and suction separation. This paper presents two coupled hydro-mechanical interfaces. For one, fluid flow is defined only in the transversal direction, while for the other, both longitudinal and transversal flows are accounted for. After verifying the two interfaces against established solutions, a systematic study of the uplift of a surface footing sitting on clay soil (modelled as Modified Cam Clay) for a range of uplift rates is described. The two interfaces have the potential to model many problems in offshore geotechnical engineering that involve lifting off the seabed.