ABSTRACT

The foundation of jack-ups is not custom-designed for a specific site. Therefore, they must be designed to remain stable, regardless of the soil conditions (Poulos, 1988). When a spudcan is installed in strong soil layer overlying weak soil layer such as sand overlying clay where there is a potential of reduction in bearing resistance as a spudcan penetrates, punch-through risk exists. Punch-through happens when the spudcan penetrates uncontrollably through the strong layer into the underlying weak layer, resulting in excessive tilting of the structure. The hull tilting condition can be worsened by additional distributed weight due to shifting of the centre of gravity of the hull towards the punchedthrough leg.A punch-through may subject the leg(s) to very large stresses and cause significant damages to the structure and equipment onboard. This is likely to cause heavy losses in terms of time and cost. A point to note is that punch-through has been occurring at an alarming rate of once per year (Osborne & Paisley 2002). This indicates the needs for improved procedures in identifying and managing such risk.