Footprint on Clayey Seabed from Spudcan Installation and Immediate Extraction

The extraction of a spudcan inevitably leaves a footprint on the seabed. Despite existing field measurements and centrifuge tests on footprint geometry, systematic studies addressing factors such as clay sensitivity and soil strength are lacking. In this study, spudcan footprints were generated through spudcan installation and immediate extraction using the large deformation finite-element (LDFE) method in ABAQUS/Explicit (version 6.14), employing the Coupled Eulerian-Lagrangian (CEL) method. The numerical model was validated with existing centrifuge test data on spudcan footprints. After the validation and before a parametric study, the footprint measurement methods were reviewed. The soil crater (SC) method determines the footprint boundary based on the shape of soil depression, distinguishing it from the soil disturbance (SD) method, which considers the disturbed soil zone. The SC method was confirmed to be more consistent than the SD method. In the parametric study, normally consolidated and overconsolidated clays with strain softening were analyzed. The influencing factors on spudcan footprints formation included spudcan diameter D, spudcan initial installation depth, and soil strength parameters, such as clay heterogeneity coefficient, soil strength ratio, and soil softening parameters. Based on all the LDFE analysis results, using the SC measurement method, all spudcan footprints were largely classified into three categories: C1: 2D-shallow, C2: 1D-medium, and C3: 1D-deep (D is the spudcan diameter). The spudcan footprint category was only influenced by clay heterogeneity coefficient, soil strength ratio, and soil softening parameters. The installation depth had no effect as long as the installation depth was deeper than 0.67D. A prediction framework on spudcan footprints was established and verified against existing centrifuge test data, which can be used in engineering practice for initial desktop studies.