TW25 UNIVERSITY OF BOLTON SCHOOL OF ENGINEERING … · Page 13 of 18 School of Engineering BEng(Hons) in Civil Engineering Semester 2 Examination 2016/2017 Ground and Water II Module

TW25

UNIVERSITY OF BOLTON

SCHOOL OF ENGINEERING

BEng(HONS) IN CIVIL ENGINEERING

SEMESTER 2 EXAMINATION 2016/2017

GROUND AND WATER II

MODULE NO: CIE5005 Date: Tuesday 16 May 2017 Time: 10.00 – 1.00 INSTRUCTIONS TO CANDIDATES: There are TWO Sections; A and B. You will be supplied with TWO Answer

Booklets by the Invigilator. Answer Section A in ONE Answer Booklet, and Section B in the other.

Section A : Q1 to Q4 (Answer THREE

Questions from four). Section B : Q5 to Q7 (Answer TWO

Questions from three). Formulae and Definitions are provided. Lined Graph Paper and Supplementary

Answer Sheets are available for your use.

Ensure that you write your Candidate

Number or Desk Number on each Figure, Supplementary Sheet or Sheet of Graph Paper you use to answer the selected questions.

All questions carry equal marks. Marks for parts of questions are shown

in brackets.

Page 2 of 18 School of Engineering BEng(Hons) in Civil Engineering Semester 2 Examination 2016/2017 Ground and Water II Module No. CIE5005

SECTION A

1a) With the aid of sketches explain the importance of water tower locations and their importance in a water distribution network.

(6 marks)

b) Determine the flows in each pipe in the distribution network shown below and calculate the available pressure head node B and C if the pressure at Node A is 400KPa. Table Q1b is provided. Perform no more than two iterations.

Fig Q1.1b

Pipe Length (m)

Diameter (mm)

Darcy Friction Factor (λ)

A - B 500 225 0.0337

B - C 400 200 0.0354

A - D 300 225 0.0337

C - D 550 200 0.0353

Fig Q1.2b

(14 marks)

Total 20 marks

Please turn the page


2

a) With the aid of sketches explain what is meant by the laminar sub-layer and how it varies with Reynolds Number.

(8 marks)

b) Water flows at 11l/s through a 100mm diameter uncoated cast iron pipeline,

175m long. Using appropriate methods determine the headloss across the pipe. Assume a dynamic viscosity µ=0.0014kg/ms.

Blasius Equation

λ = 0.316Re−0.25

Barr Equation

89.0

e

s

R

1286.5

d7.3

klog2

1

(12 marks)

Total 20 marks

3 a) List the rules commonly used for pipe network analysis

(5 marks)

b) A service reservoir provides water to a reservoir through a 450mm diameter, 750m long pipeline at a rate of 350l/s. The pipe material is unglazed clayware with sleeved joints, for which a Darcy friction factor λ=0.0132 can be assumed. After 15 years the flow demand has risen to 530l/s. To ensure that the new water demand is met a 525mm diameter clayware pipe λ=0.0130 is to be laid in parallel to the original pipeline. Assuming the water levels to the reservoirs remain unchanged; determine the length of the parallel pipeline.

(15 marks)

Total 20 marks



4

a) Briefly explain the principles behind ‘Source Control’. Give some examples of techniques which are currently in use.

(8 marks)

b) Details of an old storm sewer are given below. Using the information provided verify that the drainage system can cope with a 1 in 5yr storm assuming a time of entry of 8 minutes. Table Q4b, HRS tables and a rainfall table are provided.

Pipe No

Pipe length

(m)

Pipe gradient (1 in )

Catchment Area (Ha)

1.0 120 83 0.05

2.0 90 91 0.1

1.1 75 118 0.05

3.0 100 100 0.3

1.2 80 154 0.2

Fig Q4.1b

(12 marks)

Total 20 mark


Pipe Length Diameter

1st estimate

2nd estimate

(m) (mm) Q1

(m3/s)

hf across

Pipe (m) hf/Q1

Q2

(m3/s)

hf across

Pipe (m) hf/Q2

A - B

500 225

B - C

300 200

A - D

400 225

D - C

550 200

Table Q1b. To be handed in with answer book Candidate ID No …………………………………

Pipe

length

ref No

Pipe

Length

(m)

Pipe

gradient

(1 in )

Vel

(m/s)

Time

of

flow

(min)

Time

of

Conc.

(min)

Rate of

rainfall

i

(mm/hr)

Imp.

Area

(ha)

Cumulative

Imp. Area

AP

(ha)

Flow

Q

(l/s)

Pipe

dia.

(mm)

1.0

120 83 0.05 150

2.0

90 91 0.1 225

1.1

75 118 0.05 225

3.0

100 100 0.3 225

1.2

80 154 0.2 300

Table Q4b. To be handed in with answer book Candidate ID No .......................................................





END OF SECTION A QUESTIONS



SECTION B 5. a) Explain the purpose of “Mohr’s stress circles”. Sketch a Mohr’s stress circle

diagram for the situation where a triaxial compression test on a cylindrical clay

sample has a hypothetical shear plane inclined at an angle of from the horizontal. Ensure that you label all axes and key points on your sketch diagram and denote the direction of the principal stresses so that your diagram clearly indicates the purpose of having plotted the diagram.

(4 marks)

b) A series of ‘quick’ unconsolidated undrained triaxial tests were conducted on a sample of clay with the results obtained being as follows:

Test Number 1 2 3

Cell Pressure (kN/m2) 40 80 160

Vertical Stress at Failure (kN/m2) 111 156 235

Using a sheet of graph paper and constructing Mohr’s stress circles, determine the shear strength parameters of the soil sample and then using these values describe the clay soil being tested.

(8 marks)

c) Describe the full range of shear strength testing methods available for different soil types used in the field. Ensure that your discussions address the advantages and limitations of the methods presented.

(4 marks)

d) Explain the significance of the term ‘peak’ and ‘residual’ shear strength in a “sensitive” clay for geotechnical design situations, providing one example of a civil engineering situation in which these parameters might affect the design.

(4 marks)

Total 20 marks



6. a) A flexible foundation of length 4m and breadth 3m is to exert a uniform pressure of 175kN/m2 on the surface of a 10m layer of soil with a bulk unit weight of 21kN/m3. Using Figure Q6a, determine the immediate settlement under the centre of the foundation if the elastic soil stiffness (E) is assumed to be 4MN/m2.

(6 marks)

b) A flexible foundation of length 4m and breadth 3m is to exert a uniform pressure of 175kN/m2 on the surface of a layer of soil of assumed infinite thickness with a bulk unit weight of 21kN/m3. Using Figure Q6b, determine the total stress at a depth of 5m beneath a corner of the foundation.

(5 marks)

c) The following results were obtained from an oedometer test on a specimen of saturated clay obtained at a depth of 3m below ground level:

Applied Stress (kN/m2)

0 25 50 100 200 400 800

Void Ratio 0.990 0.955 0.926 0.885 0.838 0.789 0.743

i) Determine the value of mv for an effective stress range from

60kN/m2 to 175kN/m2. (6 marks)

ii) Calculate the consolidation settlement for a 6m thick layer of this

clay, when the effective stress changes from 60kN/m2 to 175kN/m2.

(3 marks)

Total 20 marks



Figure Q6a



Fig Q6b



7. a) Briefly explain the following terms;

i) N-C Clay (1 mark)

ii) O-C Clay (1 mark)

b) Explain in detail the process referred to as ‘consolidation’ using full geotechnical reference to all parameters you deem relevant and ensuring that you include the reasons for time dependency of this process in different soil types. You are required to use appropriate geotechnical terminology throughout your explanation.

(6 marks)

c) Using Figure Q7c determine the total stress, pore water pressure and

effective stress at each strata change and at the location of the water table and hence plot a graph to illustrate their variation with depth from ground surface to a depth of 15m below ground level. The water table is located at a depth of 5m below ground level within a 9m thick deposit of sandy gravel overlying 6m of clay.

(12 marks)

Total 20 marks



Sandy Gravel

Bulk Unit Weight = 19kN/m3 5m

Saturated Unit Weight = 20kN/m3

Water

Table

4m

Clay

Bulk Unit Weight = 19.5kN/m3 6m

Saturated Unit Weight = 21.5kN/m3

NOTE: Assume that Unit Weight of Water = 10kN/m3

Figure Q7c



Formulae

i = qB . I

Eu

e = H . (1 + eo) mv = e . (1)

H (1 + eo)

v' = v - u H = mv v

' H

v = q I

Tv = ( cv t ) / d2

END OF PAPER

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TW25 UNIVERSITY OF BOLTON SCHOOL OF ENGINEERING … · Page 13 of 18 School of Engineering BEng(Hons) in Civil Engineering Semester 2 Examination 2016/2017 Ground and Water II Module