How Do Soil Bearing Capacity Tests Support the Construction of Offshore Wind Turbine Foundations?

As offshore wind energy expands, the design of wind turbine foundations becomes increasingly critical. These massive structures must endure not only the weight of the turbine but also extreme environmental loads from waves, currents, and wind. Soil bearing capacity tests¹ serve as the backbone of foundation design, helping engineers understand how different types of marine soil respond to stress. By applying advanced testing techniques, project teams can confidently select and optimize foundation systems—ensuring safety, efficiency, and long-term performance at sea.

Static Plate Load Tests to Evaluate Seabed Soil Capacity for Monopile Foundations

Monopile foundations are widely used in offshore wind farms, especially in shallow to moderate water depths. To ensure they won’t excessively settle or tilt, engineers conduct static plate load tests² on the seabed to evaluate soil strength and deformation behavior³ under real-time loading.

How It Works:

• A steel plate is placed on the prepared seabed.
• Incremental loads are applied using hydraulic or ballast systems.
• Settlement is recorded at each load step until bearing failure or design load.

This test helps verify whether the seabed can safely support large-diameter monopiles without unacceptable vertical displacement.

Cone Penetration Tests in Soft Marine Soils for Jacket Foundation Design

Jacket foundations—used for deeper waters—rely on piles driven into soft or layered marine soils⁴. Cone Penetration Tests (CPTs)⁵ are essential for profiling these sediments and ensuring pile embedment depth and stiffness⁶ are sufficient.

CPT Features:

• Measures tip resistance, sleeve friction, and pore pressure.
• Performed from floating or jack-up platforms.
• Provides continuous data with depth—ideal for variable marine deposits.

CPT data allows engineers to simulate lateral pile behavior and ensure jacket legs resist dynamic wind and wave forces.

Borehole Shear Tests to Analyze Soil–Structure Interaction of Suction Caisson Foundations

Suction caisson foundations function like inverted buckets⁷, using negative pressure to anchor into the seabed. To assess their interface behavior and lateral capacity, borehole shear tests (BSTs)⁸ are used during geotechnical investigations.

How BSTs Work:

• Conducted in a pre-drilled borehole using a cylindrical probe.
• Shearing occurs radially along the borehole wall.
• Measures in-situ shear strength without removing the sample.

BSTs offer localized shear data vital for mooring, anchoring, and overturning resistance of suction caissons.

Seismic Soil–Foundation Interaction Tests for Earthquake-Resistant Design of Offshore Wind Turbines

Offshore wind farms near tectonic zones—like Japan or California—require design consideration for seismic events. Specialized tests assess how soil and foundation systems respond together under cyclic or dynamic loads.

Key Testing Methods:

• Cyclic triaxial testing of marine clays and sands.
• Shake table testing of soil–foundation models.
• Numerical simulations calibrated with test data.

These tests ensure turbine foundations can withstand seismic loading without loss of capacity, safeguarding both structure and grid reliability.

Conclusion

Soil bearing capacity tests are the silent engineers behind every offshore wind turbine foundation. From plate load testing of monopiles to seismic assessments of soil–structure systems, each method plays a vital role in ensuring safety, performance, and environmental resilience. As offshore wind continues to grow, these tests will remain key to anchoring our renewable energy future—firmly and sustainably.