ENEN20002 Earth Processes for Engineering Page 1 of 13
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Final 2019
Earth Processes For Engineering (University of Melbourne)
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Final 2019
Earth Processes For Engineering (University of Melbourne)
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Department of Infrastructure Engineering
ENEN20002 Earth Processes for Engineering
End of Semester 1 2019
Reading Time: 15 minutes – no writing or annotating allowed anywhere
Writing time: 120 minutes
This paper has 15 pages including this page and any Appendices.
Instructions to Students
• No annotating is allowed in reading time or after the end of writing time.
• Possible marks total 120 in 120 minutes of examination.
• Questions are NOT of equal weight. The numbers in parentheses at the end of each question
indicate the marks allocated to that question. Note that these are NOT percentage marks.
• ALL 6 questions should be attempted.
• Candidates should attempt questions 1 to 2 and questions 3 to 6 in two SEPARATE SCRIPT
BOOKS.
• Start the answer to each question on a new page in the script book and write the question number
in the top right-hand corner.
• Ensure your student number is written on all script books and answer sheets during writing time.
• On the front cover (top left-hand corner) of each script book, tick the numbers of questions
that have been attempted.
• Answer all questions on the right-hand lined pages of the script book. The left-hand unlined pages
of script books are for draft working and notes and will not be marked.
• Candidates need to ensure that the relevant student enrolment number is provided at the top right-
hand corner of the graph on pages 14 & 15 when it is submitted as part of your answer for
Question 6.
• Mobile phones, tablets, laptops, and other electronic devices, wallets and purses must be placed
beneath your desk.
• All electronic devices (including mobile phones and phone alarms) must be switched off and
remain under your desk until you leave the examination venue. No items may be taken to the toilet.
Exam Paper MUST NOT be lodged with Baillieu Library
Instructions to Invigilators
• This exam paper MUST NOT leave the exam venue
• Two 14 page script books are to be provided to each candidate; each candidate should attempt
questions 1 to 2 and questions 3 to 6 in two SEPARATE SCRIPT BOOKS.
• Provide extra script books on request
Authorised Materials: Drawing instruments including scale rules, compasses and protractors may be
used.
Calculators: Casio fx82 or fx100 calculators are permitted
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Page 2 of 15
***** ATTEMPT QUESTIONS 1 TO 2 IN A SEPARATE SCRIPT BOOK *****
Question 1
(a) Which one or more of the following four statements provides information about weather (as
opposed to climate)?
A. The average monthly rainfall in April at Melbourne Airport is 43.0 mm.
B. The rainfall at Melbourne Airport on the 15th of April 2019 was 5.8 mm.
C. On average April is the sixth hottest month at Melbourne Airport.
D. The maximum daily temperature at Melbourne Airport on the 7th of April 2019 was 22.8 ºC
(2 marks)
(b) Draw a diagram of the vertical global atmospheric circulation cells, name the cells and briefly
explain why the circulation forms this way.
(7 marks)
(c) The following diagram shows the seasonal pattern of extraterrestrial radiation at the top of the
atmosphere above four locations (A, B, C and D) on the Earth’s surface.
(i) Which of these locations are in the Northern Hemisphere (list between zero and four
locations by letter)? Briefly explain your answer.
(3 marks)
(ii) Which of these locations is closest to one of the Poles (could be either North or South
Pole). Briefly explain your answer?
(2 marks)
(Question 1 continued on the next page)
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Page 3 of 15
(d) The following diagram shows the actual vertical temperature profile (environmental lapse rate)
of the atmosphere and the lifting condensation level at a location. The diagram also shows a
parcel of air in the atmosphere and the dry adiabatic lapse rate (the rate of cooling the parcel of
air would follow if the parcel were to rise higher).
(i) Does this diagram show stable or unstable atmospheric conditions? Briefly explain your
answer.
(2 marks)
(ii) If the parcel of air were to rise to the lifting condensation level, provide a brief
explanation of how rainfall would be generated in this situation.
(4 marks)
(Question 1 continued on the next page)
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Page 4 of 15
(e) A house in Singapore (latitude 1.28º north, longitude 103.83º east) has an eave over a south
facing window as shown in the diagram below. For this house, what would the smallest (most
negative) and largest (most positive) solar noon zenith angles be over the year (the Tropic of
Cancer is located at 23.5º north, the Equator at 0º and the Tropic of Capricorn at 23.5º south)?
Would the window be fully shaded by the eave at the height of summer? Would sunlight shine
through the window in winter? Justify your answer.
(5 marks)
(f) In terms of atmospheric processes, describe briefly how the greenhouse effect works? Distinguish
between the greenhouse effect and the enhanced greenhouse effect.
(5 marks)
(Total marks for Question 1 = 30)
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Page 5 of 15
Question 2
(a) Draw a diagram of the catchment water cycle and label the important fluxes and stores of water.
(7 marks)
(b) For the last 76 years, the average annual rainfall for the Entwash River catchment was 1,250
mm, the average annual potential evapotranspiration was 2,200 mm and the average annual
runoff from the catchment was 125,000 ML. The Entwash River catchment area is 250 km2.
(i) What was the average annual runoff depth in mm?
(2 marks)
(ii) Estimate the runoff coefficient (also known as the runoff ratio).
(1 mark)
(iii) Estimate the average annual actual evapotranspiration in mm.
(1 mark)
(iv) What assumption did you make in answering (iii)?
(1 mark)
(Question 2 continued on the next page)
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(c) You have a one store catchment model that represents baseflow, evapotranspiration and surface
runoff due to saturation excess. The following information is available.
• The initial soil water storage, S, (i.e. at the start of the day) is 160 mm.
• The soil water storage capacity, Smax, is 320 mm.
• The rainfall for the day is 60 mm.
• 30% of the catchment area is saturated.
• All rainfall falling on the saturated area can be assumed to runoff as surface runoff and it
can be assumed that the saturated area does not change during the day.
• The potential evapotranspiration (PET) for the day is 4 mm.
• The actual evapotranspiration can be calculated as AET = PET × S / Smax
• The baseflow for the day is 6 mm.
• The catchment area is 250 km2.
(i) Estimate the actual evapotranspiration for the day.
(1 mark)
(ii) Estimate the surface runoff depth for the day.
(2 marks)
(iii) Estimate the total runoff volume for the day.
(2 marks)
(iv) Estimate the soil water storage at the end of the day.
(3 marks)
(Total marks for Question 2 = 20)
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Page 7 of 15
***** ATTEMPT QUESTIONS 3 TO 6 IN A SEPARATE SCRIPT BOOK *****
Question 3
(a) Draw a diagram linking together and labelling the three main rock types and two
intermediate stages between those rock types. Label the processes that link these rock types
and stages together.
(6 marks)
(b) Briefly explain the four factors that influence the degree of ground surface movement in
response to a nearby earthquake.
(4 marks)
(Total marks for Question 3 = 10)
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Page 8 of 15
Question 4
(a) A soil specimen is 40 mm in diameter and 80 mm long and in its natural condition weighs
180.57 g. When dried completely in an oven the specimen weighs 130 g. The value of
specific gravity is 2.6. What is the degree of saturation of the specimen?
(6 marks)
(b) A soil sample was taken from a building construction site to investigate the suitability of the
ground for a planned construction. Laboratory tests confirmed the following physical
properties of the soil sample;
Total density = 2000 kg/m3
Moisture content (on dry mass basis) = 40%
Specific gravity = 2.75
(i) Explain (without any calculation) why it is more meaningful to use dry density in
engineering construction compared to total density?
(1 mark)
(ii) Engineers’ predictions show that the ground needs at least 1500 kg/m3 dry density to
confirm the required stability for the construction. Is this ground suitable for the
planned construction under natural ground conditions? Discuss and provide the
required calculations.
(5 marks)
(iii) How can you improve the ground to achieve the required stability? Explain how that
method improves the ground stability without any calculation.
(1 mark)
(c) Explain the major differences between Montmorillonite and Kaolinite clay minerals? Which
one is more reactive and why? Explain the answer using their layer structures.
(2 marks)
(Total marks for Question 4 = 15)
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Question 5
(a) What are the two water retention mechanisms in soil? Why is fine-grained soil more capable of
retaining water than coarse-grained soil?
(2 marks)
(b) A sample of soil has been taken 1 m above an existing water table. Would you expect this
sample to be saturated? Explain your answer.
(1 mark)
(c) A sand castle can stand up stable when the sand is slightly moist. It would collapse if the sand is
saturated, and it will not be stable either when the sand is completely free of water. Explain the
above.
(2 marks)
(d) Figure 5.1 shows a vertical cross-section beneath a site where clay and sandy soils have been
separated along a vertical interface. The moisture content (by dry mass)/suction characteristic
curves for both soils have been determined in the laboratory and are shown in Figure 5.2.
(Question 5 continued on next page)
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(i) If there is no moisture movement within the ground and the moisture content of the
sand is 15%, determine the moisture content of the clay.
(2 marks)
(ii) During a wet season, the moisture contents of the sandy soil and clay increased by 8%
and 2% respectively. Do you expect any flow of water from one soil type to the other?
If yes, which direction would water flow, and why?
(3 marks)
(Total marks for Question 5 = 10)
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Question 6
(a) Explain why drainage influences shear strength? Provide an example to demonstrate that the
shear strength of a saturated soil of low permeability can be improved by actively promoting soil
water drainage.
(2 marks)
(b) How does liquefaction occur during an earthquake? Explain using the effective stress principle.
(2 marks)
(c) The following results were obtained from a consolidated drained triaxial test conducted on
saturated clay specimens.
Test Number Confining Stress (cell pressure) Deviator Stress at Failure
1 100 kPa 332 kPa
2 150 kPa 380 kPa
3 175 kPa 395 kPa
Table 6.1
Determine the shear strength parameters of the clay (cohesion, c’ and friction angle, ’). Show
the graphical part of your answer in Figure 6.2.
(8 marks)
(d) It is required to build an indoor stadium on the given ground in Figure 6.1 and it is decided to
build the stadium on top of a 6 m × 6 m raft foundation. The anticipated load on the foundation
from the stadium is 2880 kN. As shown in Figure 6.1, the ground consists of a 4 m thick coarse-
grained sand layer resting on a 4 m thick clay layer. Stable soil is found below the clay layer.
The water table is located 4 m below the ground surface (Figure 6.1). Some of the physical
properties of the coarse-grained sand and the clay available in the ground were obtained from
laboratory experiments and are given in Table 6.2.
Soil Type The lateral
earth pressure
coefficient at
rest condition
(Ko)
Drained
cohesion
(C’)
Drained
friction
angle
(’)
Dry density
(d)
Saturated
density
(s)
Coarse-grained
sand
0.4 10 kPa 32o 1600 kg/m3 1800 kg/m3
Clay 0.5 12 kPa 20o 1500 kg/m3 2000 kg/m3
Table 6.2
(Question 6 continued on next page)
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In order to check the stability of the ground against the construction, a soil element (A), located at
the centre of the clay deposit was considered for stability analysis (see Figure 6.1). With taking the
ground surface as horizontal and gravitational acceleration (g) as 10 m/s2;
(i) Calculate the total vertical and horizontal stresses applying on the soil element under
the natural ground condition and draw the relevant Mohr circles in Figure 6.3.
(4 marks)
(ii) Calculate the total vertical and horizontal stresses applying on the soil element after the
stadium construction and draw the relevant Mohr circles in Figure 6.3.
(3 marks)
(iii) If a 20 kPa temporary pore water pressure increment happens in the considered soil
element just after the stadium construction, draw the effective stress Mohr circles for
the soil element for both short-term and long-term after the construction conditions in
Figure 6.3.
(4 marks)
(iv) Check the stability of the ground after the stadium construction.
(2 marks)
(v) Find the directions of the failure planes.
(3 marks)
(vi) Find the directions of the planes that exhibit a 10 kPa shear stress.
(4 marks)
(vii) Find the shear stresses acting on a plane 30o to the horizontal direction.
(3 marks)
(Question 6 continued on the next page)
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Note:
• All graphical parts of your answers should be drawn in Figures 6.2 and 6.3. Figures 6.2 and 6.3
should be detached and submitted with your answer book. Make sure you put your student number
at the top right-hand corner of the pages.
• Please clearly name each of your Mohr circles in Figure 6.3.
(Question 6 continued on next page)
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Student No.
Figure 6.2
(Question 6 continued on next page)
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Student No.
Figure 6.3
(Total marks for Question 6 = 35)
Total marks for examination = 120
END OF EXAMINATION
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