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A CASE STUDY OF WESTERMOST ROUGH OFFSHORE WIND FARM
Alastair Muir WoodLead Geotechnical Engineer, DONG Energy
Presentation to Danish Geotechnical Society 24 September 2015
DESIGNING MONOPILES IN CHALK
Reference / Acknowledgement
From DONG Energy:• Michael Mygind• Kris Wessel Andersen• Christian LeBlanc Thilsted • Morten Albjerg Liingaard
From Fugro Geoconsulting:• Brian Mackenzie• Darren Burbury• Mike Rattley
From University of Southampton• Chris Clayton
Muir Wood A., Mackenzie B., Burbury D., Rattley M., Clayton C.R.I., Mygind M., Wessel Andersen K., LeBlanc Thilsted C. and Alberg Liingaard M. (2015) Design of large diameter monopiles in chalk at Westermost Rough offshore wind farm in Meyer eds. Frontiers in Offshore Geotechnics III Taylor & Francis Group, London, vol 1 pp 723-728.
Location and Key Information Turbine Array Detail
Westermost Rough (WMR) offshore wind farm
3
Prevailing wind direction
p
p
H
M
S
Conceptual geological model
From: Lord et al., 2002
Load
PileIntact
Chalk
Remoulded Chalk
Chalk pile interface model
Behaviour dominated by Remoulded Chalk
10
P P P
yr ys y
Cyclicdegradation
Chalk remoulded due to pile driving
Structured chalk(fractured or assumed intact)
Combined behaviour(yr + ys)
Total pile displacementWeak rock modelReese (1997)
Model based on plateloading tests of
Remoulded Chalk
Load response of remoulded chalk
11
P
yr
𝑦𝑟 𝑚𝑎𝑥= ??
𝑃
𝑦𝑟= ??
762mm pile
Load
100x100x12mm
angular channel
welded to pile
Remoulded chalk
13
Load response of remoulded chalk
14
P
yr
𝑦𝑟 𝑚𝑎𝑥 = tr ≈𝑡
2𝑃
𝑦𝑟= ??
pile
Load
Remoulded chalk
PD
tr
𝑃
𝑦𝑟=𝐷
𝑡𝑟×𝑀
Constrained modulus
Load response of remoulded chalk
16
P
yr
𝑦𝑟 𝑚𝑎𝑥 = tr ≈𝑡
2
𝑃
𝑦𝑟=𝐷
𝑡𝑟×𝑀
Final design at Westermost Rough
A CASE STUDY OF WESTERMOST ROUGH OFFSHORE WIND FARM
Alastair Muir WoodLead Geotechnical Engineer, DONG Energy
Presentation to Danish Geotechnical Society 24 September 2015
DESIGNING MONOPILES IN CHALK