Leg Penetration Analysis (LPA) and installation

A Leg Penetration Analysis (LPA) is performed to determine expected penetrations and indicate any risks associated with installation of the jack-up. It is typically performed as part of an SSA, but can be performed stand-alone as well. LPAs are performed strictly in compliance with ISO 19905-1:2023, including complex multi-layer interaction, squeezing and punch-through mechanisms.

The following key items are addressed:

• Seabed features inc. footprints
• Rapid penetration and Punch-through
• Hang-up
• Backfill
• Settlements
• Scouring
• Leg extraction
• Expected penetrations

The dedicated 2-page or 3-page report includes lower-bound and upper-bound penetration resistance graphs, a risk assessment with recommended mitigative measures and recommended preloading guidance. All information is presented in tables and graphs to ensure high readability.

LPAs are offered at a short delivery time and include unlimited revisions to accommodate to any changes in the project.

A Leg Extraction Analysis (LEA) is performed to determine the required pulling force for leg extraction. It is used to provide operational guidance for a smooth leg extraction and, in the worst cases, to address the risk of the jack-up being unable to independently vacate the site.

The report presents the upper-bound and lower-bound extraction resistance curves as well as the active and passive leg pulling capacity. Cases with and without a functioning jetting system are assessed.

The analysis is performed in accordance with state-of-the art industry practice, taking into account resistance of soil above and below the spudcan as well as side-friction and effects related to the duration of the stay.

Operational guidance with respect to leg extraction is provided in addition to a risk assessment and proposed mitigative measures.

A punch-through tolerance assessment addresses the consequences of an unmitigated punch-through event including the risk of progressive structural failure of the jack-up. It presents detailed preloading guidance to minimize the risks, including mitigative measures such as leg-by-leg preloading and stepwise preloading whilst maintaining a draft.

The analysis addresses the following items:

• Leg travel
• hull tilt
• resulting freeboard
• leg moments and forces
• structural strength

Punch-through tolerance assessment reports are offered to address and mitigate risks associated with punch-through or rapid penetration during jack-up installation. The reports are suitable for third-party review. The proposed guidance is suitable for direct implementation on-board.

A geotechnical risk assessment is an in-depth analysis of geotechnical risks associated with going-on-location, preloading, elevated operation, storm survival and going-off location of a jack-up at a specific site. The aim of the geotechnical risks assessment is to classify risks, quantify mitigative measures, support ALARP risk operations and to be included in HAZOP studies.

Geotechnical causes of risks include presence of boulders and unexploded objects (UXO), irregular bathymetry and footprints, loose or weak top soil, rocky seabed, seismic activity (earthquake), insufficient geotechnical data and complex or irregular soil layering. Geotechnical risks include scouring, liquefaction, settlement, punch-through, sliding and leg-splay leading to leg moments and Rack-Phase Difference (RPD).