CIVE5975 Foundation Engineering
CIVE5975/CW1/2024 Foundation design for a cable car pylon
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 public transport cable car system, is to be constructed in Kingston upon Hull along the northern bank of Humber river. The system will have a total of 8 cars with a capacity of carrying 8-10 persons/car and will stretch over 4km. Each car is 2mx 1.8mx 2m and attains a maximum speed of 8m/s. Towers are located 300m apart, and each tower has an overhang of 3m on either side with cables (thickness of 1.5inches) for cars in opposite directions.
You are required to design the foundation for an intermediate tower/pylon of 2m diameter and 28mhigh, on top of a concrete pedestal (2.5mx 2.5m) of 2m height. The area around each tower is made of 0.5m thick block paving such that the surface of the block paving is at the original ground level. Assume an imposed traffic load of 5kPa from the surrounding traffic.
Requirements
You must produce design calculations for three foundation schemes for an intermediate twor/pylon. 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
|
Soil type
|
Unit weight
|
Cohesion
|
Angle of shearing resistance
|
Undrained*
shear
strength kPa
|
SPTN
|
Coef. of volume change
|
|
m
|
|
kN/m³
|
kPa
|
|
|
|
m²/MN
|
|
0 – 0.3
|
Topsoil
|
16
|
3
|
20
|
-
|
-
|
-
|
|
0.3 – 2.1
|
Firm clay
|
19
|
0
|
25
|
0.6σv’
|
-
|
0.1
|
|
2.1 – 5.3
|
Soft silty clay
|
17
|
0
|
20
|
0.3σv’
|
-
|
0.5
|
|
5.3 – 6.2
|
Medium dense sand
|
17
|
0
|
27
|
-
|
15
|
-
|
|
6.2 – 13.5
|
Firm clayey silt
|
21
|
10
|
30
|
90 + 20z
|
-
|
0.09
|
|
13.5 – 18.4
|
Stiff to very stiff clay
|
22
|
20
|
39
|
225+3z
|
|
0.05
|
|
>18.4 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/ sandy silt including disposal
|
m3
|
80
|
|
Excavation in clay/ clayey silt including disposal
|
m3
|
120
|
|
Excavation in gravel and made ground including disposal
|
m3
|
150
|
|
Excavation below water table (additional cost)
|
m3
|
50
|
|
Imported fill
|
m3
|
80
|
|
Mass concrete
|
m3
|
60
|
|
Reinforced concrete
|
m3
|
120
|
|
Steel piles
|
tonne
|
1050
|
|
CFA piles
|
tonne
|
750
|
|
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
|
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 1st November 2024.
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 15th November 2024.
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 20th December 2024.
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 Black, Times New Roman, 11pt with single line spacing. Headings (Blue/Black, Times New Roman, 11/12pt) 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 in A4 size.
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 identification 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.