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Lars Beuth, Deltares
Numerical Studies of Offshore Monopile Installation
1. Offshore wind turbine foundations
2. Monopile installation simulations – FLOW NS-VIP
3. Next steps
In coming years hundreds of wind turbines installed in European offshore wind farms.
Cost reduction is crucial to raise profitability of billion € investments.
Currently, about 25 % of wind farm investment is spend on foundations.
Deltares and a large group of offshore companies realized high potential to
optimize foundation design and installation for reducing wind farm costs.
2015 estimate 10 % reduction of foundation costs possible. (faster installation, less noise, lower installation loads)
better understanding of pile installation process numerical studies.
Vibrating 10 times faster
than hammering.
Hammering, same location
Source: VIBRO
Pile drivability When can a pile be vibrated into the seafloor, when is impact
driving necessary?
How do factors such as sand density, vibrator frequency,
hammer load, pile diameter influence installation speed?
Soil response to wind and wave loading How does installation influence
lateral pile-soil stiffness? (for different sand densities, vibrator frequencies, hammer
loads, pile diameters)
Rotation over lifetime limited to 1°
Regulatory
bodies informed
2014 VIBRO consortium
2014 VIBRO project
• 3 monopiles vibrated, 3 monopiles hammered in Cuxhaven sandpit.
• Changes of soil density measured through CPT before and after installation.
• Lateral load tests on monopiles to investigate difference in lateral stiffness between
vibrating and hammering.
Source: VIBRO
2015 FLOW NS-VIP project
Extend Cuxhaven study through numerical analyses of pile installation.
Source: VIBRO
1. Offshore wind turbine foundations
2. Monopile installation simulations – FLOW NS-VIP
3. Next steps
• Large soil deformations
• Dynamic and cyclic loading under high frequencies
• Saturated sand
• Generation and dissipation of excess pore water
pressures
• Liquefaction along vibrated pile
• Sand is complex material with stiffness, strength, dilation
depending on density and stress, a wide range of soil
stresses occurs
• Soil-structure interaction along monopile surface
Requirements numerical analyses
Stresses
Simulation of pile installation with the Material Point Method (MPM)
AL-Kafaji, 2013
• Arbitrary large soil deformations
• Advanced modeling of water-saturated soil
• Modeling of soil-structure interaction
Excess pore pressures
MPM is unique in simulating 3D dynamic and quasi-static problems
involving …
Ceccato, 2014
Initial position of material points
Final position of material points
deformed mesh at true scale
Updated Lagrangian FEM (UL-FEM) MPM
MPM is advancement of the Finite Element Method
Better suited for simulating large deformations
Soil density change
Nguyen, 2014
MPM analyses of CPT for calibration of model parameters
Consideration of 20° slice of axisymmetric problem
F
Pile installation Lateral load test
Extrapolation of results onto larger soil volume
Drained quasi-static small deformation analyses
Soil density in cross-section
Stresses during lateral loading,
installation effects considered
MPM well suited numerical studies cost reductions through improved design
tools, regulations, pile designs, installation procedures
First results of vibratory and hammered installation and lateral loading
1. Offshore wind turbine foundations
2. Monopile installation simulations – FLOW NS-VIP
3. Next steps
…
2016 TKI Wind op Zee R&D proposal
JIP SIMON - Simulation of Installation of Monopiles
MPM for fast and accurate predictions of
offshore pile drivability
soil response to pile loading
Recommendations for optimized and novel pile designs and
installation techniques based on extensive numerical studies
Cost reductions in wind farm
construction
Future opportunities :
• Innovation push (offshore installations, numerical studies)
• Future (large-scale) research collaborations
• Increased competitiveness of involved companies on global market
2016 TKI Wind op Zee R&D proposal
2-year JIP SIMON project
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