Spudcan Reinstallation Close to Natural Footprints Considering Strength Reduction: Insights from Single-Factor and Orthogonal Experiments

In offshore jack-up operations, it is common to reinstall spudcans close to existing footprints, which could result in asymmetric soil distribution and potential instability risks. This study investigates the mechanical behavior and stability of spudcans during reinstallation, focusing on the influence of footprint geometry, spudcan type, and offset distance. The coupled Eulerian–Lagrangian (CEL) method in ABAQUS is utilized together with soil strength reduction to assess stability. Both single-factor and orthogonal experimental designs are employed to systematically evaluate parameter effects. Results show that the footprint diameter has a greater impact than the depth, increasing the peak horizontal force by 33.4% and the moment by 10.9% due to enhanced soil asymmetry. Rectangular spudcans with tapered bases generate twice the vertical resistance and exhibit 8.8% smaller lateral displacements compared to circular spudcans. Offset distance significantly affects reinstallation performance, with adverse conditions occurring at 0.5 times the diameter of the spudcan. Orthogonal analysis further confirms that the offset distance has the greatest influence among the factors studied. These findings emphasize the necessity of considering footprint geometry, spudcan design and positioning to ensure safe and stable reinstallation, and provide guidance for engineering design and risk assessment of repeated spudcan operations.