Spudcan Foundations On Multi-Layered Soils With Interbedded Sand And Stiff Clay Layers

The ‘spudcan’ foundations for mobile drilling rigs continue to exhibit a high failure rate in the offshore oil and gas industry. Contributing to this is the more frequent use of larger jack-ups in regions with highly stratified seabeds and continual exploration in deeper and untested environments. This paper reports centrifuge modelling of spudcan foundations penetrating through multi-layered soils with interbedded stronger layers. The soil conditions tested simulate offshore strength profiles that have reported punch-through failures. The effect of soil type (and hence drainage conditions) in the critical strong layer on the likelihood of punch-through is discussed. The experimental results show that the failure was less severe for a carbonate sand layer sandwiched by soft clay layer compared to that for a silica sand layer, in spite of the higher critical state friction angle of the carbonate sand.