1
SCHOOL OF ARCHITECTURE, COMPUTING &
ENGINEERING
Submission instructions
|
Online submission All pages to be numbered sequentially |
Module code | EG6102 | ||
Module title | Geotechnical Engineering Design | ||
Module leader | Dr John Walsh | ||
Assignment tutor | Dr John Walsh | ||
Assignment title | Exam Replacement Task – Coursework | ||
Assignment number | 2 | ||
Weighting | 50% | ||
Handout date | Wednesday April 1st May 2020 To be released on Moodle |
||
Submission date | Monday June 15th 2020 To be submitted online |
||
Learning outcomes assessed by this assignment |
1 – 13 | ||
Turnitin submission requirement |
Yes | Turnitin GradeMark feedback used? | No |
UEL Plus Grade Book submission used? |
No | UEL Plus Grade Book feedback used? | No |
Other electronic system used? |
No | Are totally electronic? submissions / feedback | No |
Additional information | None |
2
Form of assessment:
Individual work Group work
For group work assessment which requires members to submit both individual
and group work aspects for the assignment, the work should be submitted as:
Consolidated single document Separately by each member
Number of assignment copies required:
1 2 Other
Assignment to be presented in the following format:
On-line submission
Stapled once in the top left-hand corner
Glue bound
Spiral bound
Placed in a A4 ring bound folder (not lever arch)
Note: To students submitting work on A3/A2 boards, work has to be
contained in suitable protective case to ensure any damage to work is
avoided.
Soft copy:
CD (to be attached to the work in an envelope or purpose made wallet
adhered to the rear)
USB (to be attached to the work in an envelope or purpose made
wallet adhered to the rear)
Soft copy not required
Note to all students
Assignment cover sheets can be obtained at the HUB before submitting the
coursework at the desk.
All work has to be presented in a ready to submit state upon submission
at the HUB. Assignment cover sheets or stationery (including staplers)
will NOT be provided by HUB staff at the point of submission. This will
mean students will not be able to staple cover sheets at the HUB.
0
EG6102 Coursework Semester B 2019–20
Instructions:
You must answer ALL of the questions
Your submission must be hand written and/or word processed, scanned as necessary and
uploaded to Moodle on or before the submission deadline.
SUBJECT: EG6102 Geotechnical Engineering Design
School of Architecture Computing & Engineering 1
Q1 Figure Q1 shows the profile of a possible failure plane for a 5.5 metre high
slope in a soil for which the unit weight and long term strength parameters are
as follows:
bulk = 18.5 kN/m3; c’ = 2 kN/m2; ’ = 25°
Figure Q1
Table Q1 shows the relevant values of the various parameters required for the
analysis as derived from the section shown in Figure Q1.
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Write My Essay For MeWidth (m) |
(degrees) |
Weight (kN) |
Length of base, L (m) |
|
Slice 1 | 2.208 | 0.3 | 19.28 | 2.208 |
Slice 2 | 2.208 | 8.2 | 49.75 | 2.231 |
Slice 3 | 2.208 | 16.2 | 67.72 | 2.300 |
Slice 4 | 2.208 | 24.6 | 71.95 | 2.428 |
Slice 5 | 2.208 | 33.6 | 59.91 | 2.650 |
Slice 6 | 2.208 | 43.7 | 26.45 | 3.052 |
Table Q1
QUESTION CONTINUED ON NEXT PAGE
5.5 m
6 |
5 |
1
4
3
2
NOT TO SCALE
SUBJECT: EG6102 Geotechnical Engineering Design
School of Architecture Computing & Engineering 2
a) Assess the factor of safety for the slip circle shown in Figure Q1 using the
Ordinary Method assuming that the slope is completely dry.
[30% of Marks]
b) Re-assess the slope again using the Ordinary Method but in this case
assuming that the slope is fully saturated.
[20% of Marks]
c) Explain what is meant by the ru value used in your calculation in parts (a) and
(b). Discuss the factors that might cause this to alter in practice and explain
how and why changes in this value are likely to affect the stability of the slope.
[25% of Marks]
d) The answers to parts (a) and (b) represent two potential failure circles out of a
potentially infinite number for any given slope.
Discuss how a full slope design would be carried out to identify the appropriate
factor of safety against slope failure for the slope design.
Your discussion should include a comparison of the use of hand and software
calculation and identify some of the strengths and weaknesses of the design
process.
[25% of Marks]
SUBJECT: EG6102 Geotechnical Engineering Design
School of Architecture Computing & Engineering 3
Surcharge 12 kN/m2
0.30 m 4.20 m |
4.70 m |
0.50 m | Soil: ’ = 36° C’ = 0 b = 19.0 |
1.00 m |
5.20 m
kN/m3
Q2 a) Check the suitability of the wall design shown in Figure Q2 to resist sliding and
overturning using Eurocode 7 Design Approach 1 Load Combination 2
assuming that the angle of friction on the base is equal to 0.75 ’.
The unit weight of the concrete in the wall can be taken as 24.0 kN/m3, the soil
behind and underneath the wall is similar and the groundwater table is located
10 metres below the base of the wall. The surcharge represents a permanent
load applied behind the wall.
You must clearly indicate ALL partial factors which you have used in your
answer.
[50% of Marks]
NOT TO SCALE
Figure Q2
QUESTION CONTINUED ON NEXT PAGE
SUBJECT: EG6102 Geotechnical Engineering Design
School of Architecture Computing & Engineering 4
b) On the basis of your results from part (a) comment, explaining fully, whether
you feel that this is an efficient design.
If this were not an efficient design explain, again giving clear reasons, how you
would improve the efficiency of the design.
[25% of Marks]
c) The design you have carried out for part (a) uses EC-7 Design Approach 1
Load Combination 2. This Design Approach also requires that a further Load
Combination, Combination 1 be considered in the full design.
Describe the different approaches adopted when defining partial factors for
Load Combination 1 and Combination 2. Discuss whether you think this is a
sensible approach to define safety factors for a geotechnical structure.
[25% of Marks]
SUBJECT: EG6102 Geotechnical Engineering Design
School of Architecture Computing & Engineering 5
Q3 a) The parties to a site investigation will typically include the following:
The Client
The Designer
The GI Contractor
Explain what each of these parties is aiming to achieve from the site
investigation process and why there might be some conflict between them.
[25% of marks]
b) Ground investigation contractors will often offer to carry out “off the shelf”
ground investigations which offer a standard package of investigation
depending mainly on the area of the site. What are the potential disadvantages
to a Developer who may procure one of these for his site?
[25% of marks]
c) Explain what is meant by a conceptual foundation design and discuss the
importance of developing a conceptual foundation design at any given site
identifying at what stage during a project such a design might most suitably be
developed and how it might play a role in the development of the ground
investigation works.
[30% of Marks]
d) You are the Engineer responsible for the design of a large industrial “shed”
building
The desk study indicates that the site is expected to be underlain by a layer of
alluvium, which is in turn underlain by a thick layer of clay. Within this clay
horizon at a depth of about 6 metres below ground level there is expected to be
a claystone (rock) band, which the geological memoir for the area suggests will
vary in thickness between approximately 0.1 and 3.0 metres, although it may
also be absent in some places.
QUESTION CONTINUED ON NEXT PAGE
SUBJECT: EG6102 Geotechnical Engineering Design
School of Architecture Computing & Engineering 6
What problems might you anticipate if the conceptual design is for the use of
piles driven to bear on the claystone band?
State, given reasons, whether you would consider this to be an acceptable
design?
[20% of Marks]
SUBJECT: EG6102 Geotechnical Engineering Design
School of Architecture Computing & Engineering 7
Q4
Figure Q4a – Profile of Undrained Shear Strength with depth
a) Use an EC7 design approach to check whether a 12 metre long 450mm
diameter CFA pile installed in a clay soil with the strength profile shown in
Figure Q4a is adequate to carry a permanent vertical load of 700 kN given that
the piles are to be designed using a total stress approach, that the value of
for design can be taken as 0.42, that a total of 600 No. piles are to be installed
and that a full series of preliminary pile load tests is to be carried out.
[20% of Marks]
b) The partial factors used in the EC-7 design approach vary with the level of pile
testing carries out.
Critically assess the basis of this variation in partial factors and comment on
whether you believe this to be a reasonable approach.
[20% of Marks]
QUESTION CONTINUED ON NEXT PAGE
z
Cu |
60 kN/m2
Cu = 60 + 6z kN/m2
SUBJECT: EG6102 Geotechnical Engineering Design
School of Architecture Computing & Engineering 8
c) The piles designed in part (a) are to be used as the foundation for a bridge
abutment where each of the abutment foundations is to be made up of a group
of 9 No. piles installed as shown in Figure Q4b, where the length of each
individual pile will be equal to 12 metres.
Use your calculations from part (a) plus any additional analyses which may be
required to assess the probable mode of failure of the pile group and to
calculate the efficiency of each pile within the group.
[45% of Marks]
NOT TO SCALE
Figure Q4b
d) Use your answer to part (c) to comment critically on whether this is an efficient
pile group.
[15% of Marks]
700 mm 700 mm
700 mm
700 mm
700 mm
700 mm
SUBJECT: EG6102 Geotechnical Engineering Design
School of Architecture Computing & Engineering 9
Q5 A 3m x 3m square pad footing is to be constructed as shown in Figure Q5.
Figure Q5
The bearing capacity of the footing, which is to carry a permanent vertical load
of 5000 kN, has been checked for the sand layer by checking EC-7 Design
Approach 1 Load Combination 1 and Load Combination 2 analyses and has
shown to be acceptable for the short term case.
a) Explain with reasons what additional calculations, if any, you would require to
check the long term bearing capacity of the footing in the sand.
[20% of Marks]
b) Explain why it is not sufficient merely to carry out the checks that have been
detailed so far in order to fully check the bearing capacity of the foundation.
Explain what additional checks you would actually need to carry out to fully
verify that the factor of safety against bearing capacity failure of the foundation
is sufficient.
[30% of Marks]
c) Use you answer to part (b) to complete the necessary additional checks to
ensure that the bearing capacity of the foundation is sufficient assuming that
the load from the footing spreads at an angle of 1 horizontal to 2 vertical in each
direction and that the drained and undrained strength parameters of the clay
are as shown in Table Q5.
[50% of Marks]
QUESTION CONTINUED ON NEXT PAGE
Clay
Sand
1.
2 m |
3 m
5 m
SUBJECT: EG6102 Geotechnical Engineering Design
School of Architecture Computing & Engineering 10
Undrained | Cu = 80 kPa | u = 0 | bulk = 19.0kN/m3 |
Drained | C’ = 0 | ’ = 23° |
Table Q5
Note: It can be assumed that the groundwater table is at a significant depth below the
base of the clay and for purposes of simplicity you should assume that the
weight density of the Sand is equal to the weight density of the Clay
i.e. For the sand: bulk = 19.0 kN/m3
SUBJECT: EG6102 Geotechnical Engineering Design
School of Architecture Computing & Engineering 11
Q6 A 5m x 4m rectangular pad footing is to be constructed as shown in Figure Q6.
Figure Q6
a) Calculate the increase in vertical stress mid way through the thickness of the
clay layer directly under the foundation if a vertical load of 10,000 kN is applied
uniformly across the pad and it can be assumed that foundation stresses are
propagated through the soil at an angle of 2:1 (vertical: horizontal).
[10% of Marks]
b) Use your answer from part (a) to calculate the total expected consolidation
settlement of the foundation if the coefficient of volume compressibility, mv, of
the clay is equal to 0.50 m2/MN.
[10% of Marks]
c) Calculate the expected consolidation settlement:
i) 2 years after the initial application of the load
ii) 10 years the initial application of the load
The coefficient of consolidation of the clay, cv, is equal to 0.10 m2/year
The increase in pore water pressure at the top surface and at the base of the
clay layer on initial loading are both equal to 85 kN/m2.
[10% of Marks]
QUESTION CONTINUED ON NEXT PAGE
Clay
Sand
1.
2 m |
6.4 m
5.6 m
Sand
SUBJECT: EG6102 Geotechnical Engineering Design
School of Architecture Computing & Engineering 12
d) Assuming the same parameters as for part (c) calculate the time taken for 90%
of the total consolidation settlement to develop
[10% of Marks]
e) Explain why it is important to carry out each of the calculations in parts (b), (c)
and (d) in any foundation design.
What are the implications of your answer in part (c) if the foundation is for a
building with a design life of 25 years?
[35% of Marks]
f) Without doing any more calculations, assess what difference it would make to
your calculations if the clay layer shown in Figure Q6 were underlain by an
impermeable soil layer rather than the sand layer shown.
[25% of Marks]
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