CIVE5975 Foundation Design
5975/CW1/2023 Foundation Design – Foundations for a wind turbine
Introduction This is an outline scheme for the foundation for a wind turbine.
Aim • to interpret site investigation data
• to identify potential hazards and failure mechanisms
• to design suitable foundations for a wind turbine
Skills • interpret site investigation data to select design parameters
• produce effective, economic design of foundations
• develop an understanding of methods used to calculate ultimate limit state and
serviceability limit state for foundations
Outcome • design of suitable foundations considering the soil conditions, the loading conditions, and
the effect of environmental loading
• an economical design
Brief Outline
A new 4MW wind turbine is to be installed near Barmston, Driffield. The mast will be 72.5m
high and support 105m diameter blades.
Requirements
You must produce design calculations for three foundation schemes for a new wind turbine.
The ground profile and the properties of the soils are listed in the table below. At this stage, a
feasibility report is all that is required. You must suggest a suitable range of foundations for
the proposed structure, which must include a shallow foundation, a deep foundation and
ground improvement schemes. The design should be technically sound, economic and safe.
Soil Conditions
A summary of the findings from a ground investigation is given below.
Depth below
ground level
m
Soil type Unit
weight
kN/m³
Cohesion
kPa
Angle of
shearing
resistance
Undrained*
shear
strength
kPa
SPT
N
Coef. of
volume
change
m²/MN
0 – 0.3 topsoil 16 0 25 - - -
0.3 – 3.0 Sandy clay 17 0 25 0.3σv
’
3.0 – 7.9 Sandy silty clay 21 0 38 0.3σv
’
7.9 – 9.4m Fine to medium gravel 20 0 27 - 18 -
9.4 – 15.4m Stiff sandy clay 21 5 37 100 + 10z - 0.1
15.4 – 17.2m Very stiff sandy clay 22 5 39 160 + 20z 0.05
17.2 – 21.8m Dense sand and gravel 21 0 45 - 30
21.8 – 26.4m Very stiff clay 22 5 39 220 - 0.05
>26.4m Chalk
* z measured from the top of the layer
Costs
The piling contractor will use either British Standard Universal Bearing Piles at £1050 per
tonne or cfa piles (300mm, 450mm, 600mm and 750mm diameter) at £750 per tonne. Shallow
foundations, foundations for pile caps and other associated excavations will cost:
Item Unit Cost
excavation in sand including disposal m3 80
excavation in clay including disposal m3 120
excavation in gravel and made ground including disposal m3 150
Excavation below water table (additional cast) m3 50
Imported fill m3 80
mass concrete m3 60
reinforced concrete m3 120
formwork support for foundations and pile caps m2 50
1200mm deep cement/soil mixing m2 120
1200mm reinforced gravel raft m2 120
Stone columns m3 70
Imported fill for preloading and disposal m3 120
Wick drains m 5
If you wish to consider other items, please request a rate.
Report There are three tasks to complete. The first two tasks will be formative, i.e. they will not be
marked but will be used to give you feedback. You need to complete these tasks to design the
foundations.
The first is an overview of the hazards including the loads and ground conditions you will
consider when designing your foundations. In addition to the hazards, you should also include
your calculations for the loads. The submission should be in the form of a fully labelled cross
section, table of hazards and calculations out in an approved manner submitted to the VLE by
the 3rd November 2023.
The second is a list of assumptions that you will make to produce the design covering the client
and statutory requirements, the technical aspects of the design (e.g., combinations of actions,
soil properties) and possible conceptual designs. You can use sections 1 to 7 of the final report
as a guide. This must be submitted to the VLE by the 10th November 2023.
You must provide at least three alternative designs with supporting calculations in your final
report. It is recommended that you consider a shallow foundation, a deep foundation and
ground improvement schemes.
The design calculations can be typed or handwritten. If you choose to submit typed
calculations, they should be presented in a similar manner to the hand calculations and be fully
explained. No matter which method you use, the presentation of the calculations will be
assessed. This must be submitted to the VLE by 15th December 2023.
The design report should include the following:-
1. A cover sheet including the title, date and name of authors
2. Summary (up to 300 words)
3. Contents list
4. Introduction including clearly stated requirements
5. Description of the load combinations
6. Description of the assumptions
7. Overview of the design methodology
8. Overview of the design
9. References
10. Appendices containing the handwritten design calculations
The body of the report (Sections 1 to 9) should be typed in Times New Roman 11pt with single
line spacing. Headings should be in bold and numbered 1, 1.1, 1.2, 2 etc. and should be
preceded by one line. Paragraphs must be single line spacing, left justified with a single line
between the paragraphs. Margins should be 2.54cm top, bottom and right and 3.17cm left.
The Harvard system should be used for references.
All tables and figures in the body of the report must have a title and be numbered. It is
important to include figures as they help the explanation. However, if a figure is included then
you must ensure that it is discussed in the report.
The calculations should be attached as an appendix. All assumptions and sources of
information should be clearly stated. Calculations should be supported by figures.
The body of the report (Sections 4 to 8) must not exceed five pages.
Marking The first two reports are formative to give you feedback on your design. No marks will be
given for late submission. The marking schedule for the final report will be as follows:-
1. Presentation 10%
2. Statement of assumptions 10%
3. Hazard identification 10%
4. Load combinations 10%
5. Design method and conceptual design 20%
6. Calculations 20%
7. Overall design 20%
You must demonstrate that your design satisfies the ultimate limit state and serviceability
criteria. In addition, you must produce a Bill off Quantities.
This final design must be submitted to the VLE by 15th December 2023.
B G Clarke
September 2023
