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 jackups 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 (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 layers compared to that for a silica sand layer, in spite of the higher critical state friction angle of the carbonate sand.