Combined loading capacity of spudcan footings on loose sand

Abstract

Experimental observations on the capacity of a spudcan footing model on loose sand subjected to combined vertical, horizontal and moment loads at stresses relevant for modern jack-up drilling units are presented. The observations are developed from drum centrifuge experiments using an apparatus capable of independently translating and rotating the footing. The results are interpreted within the framework of strain-hardening plasticity theory previously used to develop force-resultant models from flat circular footing experiments conducted at 1g. The complete combined loading yield surface for spudcan foundations on loose sand has been successfully derived through seven specially designed swipe tests. An empirical equation previously derived to describe the yield surface of flat footing is recalibrated for spudcans. A three-dimensional sliding surface that intersects the traditional yield surface has been experimentally recorded and an analytical expression derived. With model parameters being refined and the sliding surface added, the theoretical yield surface describing circular spudcan footing on loose sand is complete.