SKIRTED SPUDCANS AND PERFORATION DRILLING FOR INSTALLATION OF SPUDCANS CLOSE TO EXISTING FOOTPRINTS

摘要

The large footprints that remain on the seabed after offshore mobile jack-up platforms have completed operationsrnpresent hazardous conditions for any future jack-up installation at that site. The slope of the footprintrncauses detrimental horizontal and moment loads to be induced on the spudcan during the preloading processrnwhere only vertical loads are expected. This paper reports model tests exploring the efficiency of innovativernspudcan foundations and perforation drilling to mitigate this issue. The soil conditions tested simulate softrnseabed strength profiles close to the mudline, varying the undrained shear strength. The most critical reinstallationrnlocation and existing footprint depth were investigated. In all of the experiments, an initial footprintrnwas created. Skirted, innovative and generic spudcan models were then offset and reinstalled on nonperforatedrnand perforated sites, with the vertical and moment loads on the spudcan recorded using a highly instrumentedrnshaft. The innovative spudcan and the removal of soil inside the spudcan perimeter, with an arearnof 9% perforated, reduced the induced moment significantly.