📋 Case Study

Offshore Wind Turbine Monopile Foundation in Glacial Till

Uncertain socket depth due to variable till strength and presence of soft seams affecting lateral capacity and scour sensitivity

🏗️ Project Overview

North Sea wind farm, UK sector with stiff glacial till and interbedded silt lenses

🎯 Challenge

Uncertain socket depth due to variable till strength and presence of soft seams affecting lateral capacity and scour sensitivity

🔧 Design Approach

Integrated vibrocore + T-bar + seismic cone testing; probabilistic design using Monte Carlo simulation of undrained shear strength profiles

📐 Design Diagram

AI-generated project design illustration

📐 Key Calculations

Monopile lateral capacity (p-y curve)

p = k × yⁿ (API RP 2GEO)

Result: pₘₐₓ = 1.8 MN/m

Controlled pile head deflection < 15 mm

Scour depth estimation (Harris formula)

yₛ = 2.0 × d₅₀⁰·³ × Uᶜ⁰·⁴

Result: 4.2 m

Directed scour protection design

Probability of failure (Pf)

Monte Carlo simulation of 10,000 realizations

Result: 1.2×10⁻⁴

Met target reliability index β = 3.8

📊 Results

As-built socket depth matched predicted 22.5 m ± 0.4 m; no unplanned rework during installation

💡 Lessons Learned

• •T-bar penetration resistance correlates strongly with su in overconsolidated till
• •Probabilistic modeling justified cost premium for enhanced CPT density

✅ Key Takeaways

• 1T-bar penetration resistance correlates strongly with su in overconsolidated till
• 2Probabilistic modeling justified cost premium for enhanced CPT density