Application of Probabilistic Method in Development of PRSM

Abstract

Regional Suitability Mapping (PRSM) was initiated in 2013 with the aim of optimising operational cost efficiency and minimising potential incidents during jack-up emplacement, particularly incidents due to punch through failure. In the later stage of PRSM, a pilot study was carried out to assess punch through failure using probabilistic method. The proposed approach is found to be readily applied to multiple locations by using a standardised computational model. The probabilities of punch-through at 100 locations in Malaysian Waters were studied using this approach for Keppel FELS B Class jack-up rig in strong clay over weak clay scenario. The study indicates that the majority of boreholes fell into the extremes, either having less than 10 % probability of punch-through, or more than 90 % probability of punch-through. It was concluded that the proposed probabilistic approach enables the probability of punch-through in strong clay overlying weak clay profiles to be quantitatively computed such that the risk can be objectively evaluated. This is an advantage as compared to the standard industry practice which is to perform deterministic leg penetration analysis based on two design strength profiles corresponding to the low and high estimates.