###### Abstract
(ii) Physical mechanism complexity--Simplified models cannot adequately account for coupled factors, including cavity formation mechanisms during penetration by varying spudcan geometries [4], the spatial variability of soil properties [5], interlayer interactions in stratified soils [6], and partial drainage effects in intermediate soils (e.g., silty sand and sandy silt [7]). Building upon this foundation, recent research on spudcan punch-through incidents has primarily focused on sand-over-clay seabeds prevalent in the North Sea and South China Sea. When a spudcan penetrates the sand layer, soil arching effects develop, achieving peak bearing capacity (\(q_{\text{p}eak}\)). Upon penetrating the underlying soft clay, the bearing capacity drops abruptly, triggering rapid platform subsidence [8; 9]. The severity of this phenomenon is predominantly influenced by three factors: (i) sand layer thickness, where thicker sand layers enhance soil arching effects, elevating \(q_{\text{p}eak}\)[3]; (ii) clay undrained shear strength (\(s_{u}\)), where lower \(s_{u}\) values correlate with greater reductions in post-peak resistance (\(q_{\text{p}eak\text{p}eak}\)) [10]; and (iii) the spatial heterogeneity of clay strength, where localized weak zones exacerbate punch-through risks [11]. Numerical prediction accuracy depends critically on the appropriate selection of soil constitutive models and the spatial distribution of sand relative density and clay \(s_{u}\)[12]. For stiff-over-soft clay seabeds in Southeast Asian waters (e.g., the Malay Basin and Java Sea) and the Gulf of Mexico, [PERSON] et al. [13] proposed spudcan design optimizations with peripheral skirts and perforations to mitigate punch-through risks. However, research on multi-layered seabed punch-through mechanisms remains unexplored. Existing studies on the global anti-sliding stability of jack-up platforms have primarily focused on pre-existing seabed footprints and seabed slope effects. [PERSON] et al. [14] demonstrated via CEL large-deformation analysis that spudcan reinstallation near seabed footprints induces significant horizontal loads and overturning moments, peaking at 15% of vertical loads. Additionally, [PERSON] et al. [15] developed parametric design tables using finite element limit analysis (FELA), incorporating the cone angle, embedment ratio, and strength gradient, providing quantitative criteria for anti-sliding design. Regarding seabed slope impacts, [PERSON] et al. [16] revealed via centrifuge tests that the anti-sliding capacity of mat foundations significantly decays with increasing seabed slope. When slope angles exceed \(5^{\circ}\), the anti-sliding capacity decreases by over 20%, though increasing the leg penetration depth can enhance platform stability. For individual spudcan foundations, [PERSON] et al. [17] employed a coupled material point-finite element method (MPM-FEM) model, demonstrating that inclined seabeds alter soil bearing mechanisms and failure modes, transforming symmetrical shear failure into asymmetrical flow, thereby compromising foundation stability. These studies confirm that seabed slope parameters must be incorporated into anti-sliding stability assessments, though existing research has not comprehensively integrated operational loads or anti-overturning stability considerations. Although scholars have achieved significant results in the fields of single-spudcan penetration resistance and punch-through analysis, providing theoretical support and engineering references for penetration prediction and risk assessment, systematic research and experimental validation on the jack-up stability of self-elevating platforms remain insufficient, with notable gaps particularly in the analysis of global anti-overturning and anti-sliding stability. To address this shortcoming, an entire four-legged centrifuge test at \(150\times g\) was conducted to investigate spudcan penetration mechanisms in typical clay and sand strata, along with the evolution of global sliding and overturning behavior.