ASSIGNMENT GUIDANCE SHEET FOR COURSEWORK GEOTECHNICAL ENGINEERING 4 Semester I

STANDARD COURSEWORK RULES:

1. The School’s coursework cover sheet must be used, which can be downloaded from the School’s website.

2. The threshold grade for each problem of the coursework is Grade E. Students who fail to achieve the threshold will have to re-submit the coursework to be awarded credits for Geotechnical Engineering 4. Re- submitted work is capped at Grade D3.

3. Penaltiesforlatesubmissionareapplied.

REQUIREMENTS FOR THE FORMAT:

The submission of the coursework is in two parts:

1. Youareprovidedwithanexceltemplateforyourparameterisation/axial

capacity calculation. You may modify this to suit your chosen design solution. This is to be submitted in PDF format. The template should have minimum text size of arial 11.

2. Your assumptions, assessment of limitations and uncertainty (bullet point format) and workflow sketch in max. two A4 pages. You may include additional figures to support your analyses. Font size 11 (including figures), page margins 2.5cm for all four sides, line spacing 1.15. Reference lists are not included in the page count. This should be submitted in PDF format.

MARKING CRITERIA

1. Developmentofdesignparametersandaxialcapacitycalculationbased on the available information [35%]

2. Choice of assumptions, consideration of limitations and uncertainty. Workflow for optimisation across the windfarm [35%]

3. Presentation[20%]

4. Qualityofwriting[10%]

DEADLINE FOR SUBMISSION: 10th November 2022

You are encouraged to read some literature (textbooks and research papers).

If you have questions related to the coursework, please contact me via email.

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Geotechnical Engineering 4 - Coursework

Background information: This problem is based on ultimate limit state pile design for an offshore wind turbine to be installed in an area with water depth >40m. A total of 70 wind turbines are planned. The wind turbines will be supported by a lattice steel (jacket) structure founded on multiple driven tubular steel piles embedded into the soil beneath the seabed. Lateral wind and wave induced overturning moments are transferred through the jacket and resisted by axial push-pull (tension-compression) loading on the piles. The foundations must be sized to provide sufficient capacity to resist the ultimate loads. Typical geometries include diameters typically between 2 and 3m, embedded length to diameter ratios (L/D) of ≈7 to 20 and diameter to wall thickness ratios (D/t) of around 100.

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The problem: You have been asked by a client to carry out a concept design for the pile foundations. Your design must include defendable design parameters, and final pile geometry (embedded length, diameter and wall thickness). You are told that:

• The jacket applies net loads of 17MN in compression and 3MN in tension under each of its four legs.

• A full site investigation is not yet available but you have been provided with sufficient information to classify the soil and carry out a concept design, namely; CPTs, classification testing, and relevant laboratory element test results. Where information you require is missing, you should make reasonable assumptions based on your reading.

• You may use any design method covered in this course, as long as you can rigorously justify its use

Your work should include the following:

(a) Parameterisation and axial pile capacity calculations using the provided template. You should ensure that your final pile capacities are sufficient to support the loads applied by the jacket.

(b) A list of your necessary assumptions, assessment of limitations and uncertainty. This should be in the form of a bullet point list with supporting figures and references if necessary.

(c) A sketch of the workflow you would suggest to the client to optimise the pile design across the windfarm when the full site investigation is available.

You may assume that:

(a) The jacket legs are sufficiently widely spaced such that there are no interaction effects between their foundations.

(b) Any lateral loads or moments can be ignored and vertical axial loading only drives the design.

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