Bearing capacity on sand overlying clay soils: experimental and finite element investigation of potential punch through failure
When a jack up spudcan foundation is installed on seabeds consisting of a sand layer overlying soft clay, the potential for 'punch through' failure exists. This happens as a result of an abrupt reduction in bearing resistance when the foundation punches a block of sand into the underlying soft clay in an uncontrolled manner. This paper details an extensive series of 30 tests of flat circular and spudcan foundations continuously penetrated through samples of sand overlying clay, and performed under relevant stress conditions using a drum centrifuge. The large testing area of the drum centrifuge was used advantageously to produce test results that could be compared directly with tests covering a sand thickness over foundation diameter of 0*21 to 1*12. Results from retrospective finite element analysis of the experiments are also described, with back calculated values of the stress level dependent friction and dilation angles in the sand during peak penetration resistance shown to fit correlations in the lit.