###### Abstract  
Although wind turbine installation vessels (WTIVs) are increasingly operating in deep-water complex geological areas with larger scales, systematic research on and experimental validation of platform jack-up stability remain insufficient. This study aimed to establish a comprehensive evaluation framework encompassing penetration depth, anti-overturning/sliding stability, and punch-through risk, thereby filling the gap in holistic platform stability analysis. An entire four-legged centrifuge test at 150\(\times\)\(g\) was integrated with coupled Eulerian-Lagrangian (CEL) numerical simulations and theoretical methods to systematically investigate spudcan penetration mechanisms and global sliding/overturning evolution in clay/sand. The key findings reveal that soil properties critically influence penetration resistance and platform stability: Sand exhibited a six-times-higher ultimate bearing capacity than clay, yet its failure zone was 42% smaller. The sliding resistance in sand was 2-5 times greater than in clay, while the overturning behavior diverged significantly. Although the horizontal loads in clay were only 50% of those in sand, the tilt angles at equivalent sliding distances reached 8-10 times higher. Field validation at Guangdong Lemen Wind Farm confirmed the method's reliability: penetration prediction errors of <5% and soil backflow/plugging effects were identified as critical control factors for punch-through risk assessment. Notably, the overturning safety factors for crane operation at 90\({}^{\circ}\) outreach and storm survival were equivalent, indicating operational load combinations dominate overturning risks. These results provide a theoretical and decision-making basis for the safe operation of large WTIVs, particularly applicable to engineering practices in complex stratified seabed areas. spudcan penetration; centrifuge model test; soil plug effect; backflow; punch-through 2025202515797119  
areas and have a significantly increased leg installation/extraction frequency due to the dense distribution of WTG sites. Recent trends toward increased individual WTG capacities, expanded wind farm scales, and offshore distances have resulted in the significant escalation of variable loads (e.g., leg-encircling crane operations) and environmental loads during elevated operational phases. In this context, the leg-spudcan system is the only load-bearing structure during jack-up operations. It is necessary to make the load of each leg gradually approach the design target value via a diagonally opposite leg preload, finally enabling the whole platform to reach the stable state of static equilibrium [1]. This process is critical for ensuring the global stability of the platform under complex geological conditions and extreme loading scenarios. Spudcan penetration resistance and depth analysis (i.e., foundation bearing capacity prediction based on soil strength profiles) constitute the fundamental basis for assessing global jack-up platform stability. This involves complex geomechanical challenges, including large-deformation failure mechanisms, soil flow patterns, and backfill evolution. Recent systematic studies on spudcan penetration resistance and bearing capacity prediction in stratified seabeds have faced two primary challenges:  
(i) Theoretical limitations--Conventional SNAME/ISO standards employ shallow foundation bearing capacity formulas based on the \"projected area method\" and \"punch-through shear method,\" relying on oversimplified assumptions (e.g., linear interpolation of the transition layer bearing capacity). These approaches fail to capture critical mechanisms such as progressive soil failure (e.g., sand dilatancy effects and clay strain softening) and post-punch-through soil plug retention [2], leading to significant prediction errors in peak resistance and punch-through depth [3].