OFFSHORE SKIRT PENETRATION IN CLAY IN THE GEO-CENTRIFUGE

To study the fundamental mechanism of skirt penetration in clay, tests were performed in the large centrifuge at Delft Geotechnics. AN idealised prototype skirt pile having an inside diameter of 10.5m, a wall thickness of 1.27 m and a length of 36 m was scaled 1:150 and 1:300. The skirt models were penetrated into the clay in-flight CPT-tests were performed to measure the undrained shear strength. During penetration the force and the heave inside and outside the skirt were measured. The generated excess pore pressures in the clay were measured as well together with the dissipation afterwards. The forces, heave and excess pore pressures measured in the different tests are compared. The measured results are furthermore compared with the results of calculation models. In this paper attention is paid to the generated excess pore pressures during penetration and the dissipation afterwards. It appeared that the penetration force as well as the initial pore pressures just after penetration can be described with existing calculation models. The models on heave and consolidation need some further study.