Punch-through during jack-up installation is governed by the interaction between the spudcan, the thickness and strength contrast of the soil layers, and the constitutive and kinematic assumptions adopted in the analysis. This study presents an application-specific, validation-based finite-element assessment of the SEA-20 Razmand jack-up spudcan in a stiff-over-soft clay profile. An axisymmetric PLAXIS 2D model with an undrained Mohr–Coulomb representation was first checked against the published circular-footing benchmark of Ibrahim; at 10 mm settlement, the numerical and reference pressures differ by approximately 3%. The verified modelling workflow was then applied to a 14 m diameter spudcan subjected to a design leg load of approximately 25 MN. The upper and lower clay layers have undrained shear strengths of 21 and 5 kPa, respectively, giving a strength ratio of 0.24 and therefore a pronounced susceptibility to punch-through. The computed response exhibits the characteristic peak–drop–recovery sequence as the foundation approaches and crosses the layer interface. Comparison with the SNAME mechanism provides an independent screening-level check. The contribution is primarily application-specific and methodological: it establishes a transparent workflow for preliminary installation-risk assessment while explicitly defining the limits of small-deformation, perfectly plastic modelling. Deep post-failure penetration, cavity evolution, soil backflow, and strain-softening effects require large-deformation and advanced constitutive analyses.