Rock solid challenges: how jack-ups are adapting to tougher seabeds

As offshore wind energy expands from the sandy soils of the North Sea to new frontiers like the North Atlantic, Japan, and Australia, the industry faces a hidden but formidable challenge: rock-hard seabeds. These tougher environments test the limits of jack-up vessels, demanding cutting-edge engineering, smarter digital tools, and a deep understanding of seabed interaction.

GustoMSC, with its long-standing expertise in jack-up design, is at the forefront of enabling this transition, translating practical knowledge into innovative solutions for safe and efficient operations on hard soil and rock.

The Shift to New Offshore Frontiers

Developers are venturing into uncharted waters with unique environmental conditions. Unlike the cohesive soils of the North Sea, new sites often present dense glacial tills, coral limestone, or exposed bedrock.

• Operational Complexity: Combining greater water depths, dynamic sea states, and harder seabeds adds significant complexity to construction.
• New Challenges: Lowering jack-up legs onto these surfaces requires precise management to avoid structural damage 1.

Installing on Hard Seabeds: A Finely Balanced Dance

On paper, installation seems simple: lower the legs until the spudcans touch the seabed, then jack up. In reality, hard soils change the story dramatically.

• Impact Risks: The initial contact can trigger sudden peak loads that reverberate through the legs and hull, risking structural overstress 2.
• Uneven Terrain: Rocky seabeds often feature ridges, slopes, or cavities, introducing eccentric loads and sliding risks.
• Resonance Issues: Long-period swell waves can excite the vessel at its natural frequency, leading to high-energy impacts upon seabed contact 3.

Operating with Minimal Penetration

Once installed, the lack of deep embedment creates further challenges:

• Concentrated Pressure: Contact pressures are concentrated over smaller areas, increasing local damage risks.
• Reduced Stiffness: Minimal penetration reduces the seabed's ability to resist tilting, crucial for stability during storms.
• Sliding & Scour: Low frictional resistance on rock increases sliding risks, while scour can erode what little sediment exists 4.

However, hard seabeds do offer high bearing capacity, eliminating concerns about sinking or uneven settlement.

Engineering Insight: From Simulation to Site Support

Mitigation starts long before deployment. GustoMSC engineers use advanced time-domain simulations to model jack-up behavior under combined wave and soil interactions.

• Predictive Modeling: These models predict impact loads and structural stresses, defining safe operating envelopes.
• Practical Guidance: Results translate into clear recommendations for onboard teams, defining safe weather windows and jacking speeds 5.

Digital Tools: Operating Smarter

Digitalization bridges the gap between design and field operations. Integrated sensors monitor real-time leg loads and hull motions, allowing operators to compare actual behavior with engineering models. This feedback loop helps validate assumptions and improve accuracy for future campaigns.

Design Evolution and Collaboration

Physical mitigation measures, such as seabed preparation or alternative spudcan geometries, are also being explored. GustoMSC collaborates closely with operators and classification societies to harmonize standards and develop best practices for these new environments.

As offshore wind continues its global march, the lessons learned in Japan or the US will shape the next generation of jack-ups. Through innovation and collaboration, the industry is proving that even the hardest ground can provide a strong foundation for future growth.