TW58 UNIVERSITY OF BOLTON SCHOOL OF ENGINEERING BENG (HONS) CIVIL ENGINEERING SEMESTER ... · 2017-10-10 · Page 4 of 17 School of Engineering BEng (Hons) Civil Engineering Semester

TW58

UNIVERSITY OF BOLTON

SCHOOL OF ENGINEERING

BENG (HONS) CIVIL ENGINEERING

SEMESTER 2 EXAM 2015/2016

GROUND & WATER STUDIES 2

MODULE NO: CIE5005 Date: Tuesday 17 May 2016 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 17 School of Engineering BEng (Hons) Civil Engineering Semester Two Exam - 2015/2016 Ground and Water Studies 2 Module No: CIE5005

SECTION A

Question 1

i. With the aid of sketches explain what is meant by the boundary layer and it’s importance in pipeline hydraulics. (5 marks)

ii. The discharge of water passing through a horizontal 225Φ pressurised main varies from 0.4l/s to 22l/s.

a. Sketch the pipeline velocity profile for these maximum and minimum flows, taking the dynamic viscosity µ to be 1.14x10-3 kg/ms. (8 marks)

b. Determine the headloss is each case if the pressurised main is 80m long and has a ks

value of 1.3mm. (7 marks)

1

√λ= −2log (

ks3.7d

+5.1286

Re0.89)

Total 20 marks

Question 2

i. Explain the term ‘Sustainable Urban Drainage System’, giving some examples of the technique. (8 marks)

ii. Using the Rational Method of design, check the suitability of the drainage design in Table Q2 and select a suitable pipe diameter for pipe 1.2. The rainfall return period is 1 in 10 years, the time of entry is 6.0 minutes and the pipe roughness ks is 1.5mm. HRS tables and a rainfall table are provided. nb (12 marks)

Total 20 marks

Please turn the page


Question 3 A pipe network System A is shown below in Fig Q3a. Using the information given in Table Q3b

i. State the basic hydraulic principles which apply in water network analysis. (4 marks)

ii. Make a sensible first estimate for the head at the pipe junction in System A. Briefly explain

the reasons for your selections. (2 marks)

iii. Ascertain a first estimate of the level of error in your initial assumption using Table Q3c. Explain how you have determined the errors, what the errors mean. (12 marks)

iv. Determine the correction factor for pipe junction height. (2 marks)

Fig Q3a System A

Pipe Length

(m) Diameter

(mm) Roughness

(mm) Reservoir

Water level AOD (m)

A 720 300 1.5 1 305

B 560 200 1.5 2 289

C 650 200 1.5 3 284

Table Q3b

Total 20 marks


A

B

C

1

2

3


Question 4

i. A 300Φ sewer, length 220m and roughness ks of 1.5mm, is laid at a gradient of 1 in 125. Determine the ‘full bore’ capacity of the pipe and the height of surcharge in the upstream manhole when the flow in the sewer is 111 litres/sec. (HRS tables are provided)

(8 marks)

ii. Water flows through a 200mm diameter pipe at a rate of 40litres/sec. The pipe is 400m long and has a Darcy friction factor λ of 0.022. It is proposed to increase the flow through the pipeline to 55litres/sec, without increasing the friction loss, by the addition of a parallel pipeline of the same diameter and λ value as the existing pipeline. Determine the length of pipe required. (12 marks)

Total 20 marks



Pipe 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)

Cum. Imp. Area

AP (ha)

Flow Q

(l/s)

Pipe dia.

(mm)

Pipe

Capacity

(l/s)

1.0 95 83 0.08 150

1.1 69 67 0.13 225

2.0 150 83 0.18 225

2.1 110 56 0.12 225

1.2 76 50 0.14

Table Q2

TO BE HANDED IN WITH ANSWER BOOK Candidates ID No.………………………………



Pipe hf across

Pipe (m)

SO

(1 in)

Q

(litres/s)

Q

(m3/s)

A

B

C

Error in Q

Table Q3c

TO BE HANDED IN WITH ANSWER BOOK Candidates ID No............................................






END OF PART A QUESTIONS



SECTION B

Question 5 i) 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.

(5 marks)

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

Test Number 1 2 3

Cell Pressure (kN/m2) 30 60 120

Vertical Stress at Failure (kN/m2) 121 154 215

Using a sheet of graph paper and constructing Mohr’s stress circles, determine the shear strength parameters of the soil sample and thus describe the soil strength using geotechnical terminology.

(8 marks)

iii) Describe the full range of shear strength testing methods available for testing clays in the field and in the laboratory.

(4 marks)

iv) Using load versus deformation plots justify what you would expect to observe when carrying out a laboratory shear box test on both a loose and a very dense sand.

(3 marks)

Total 20 marks



Question 6 i) A flexible foundation of length 4m and breadth 3m is to exert a uniform pressure of

150kN/m2 on the surface of an 8m layer of soil. 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)

ii) A flexible foundation of length 4m and breadth 3m is to exert a uniform pressure of 150kN/m2 on the surface of a layer of soil of assumed infinite thickness. Using Figure Q6b, determine the total stress at a depth of 5m beneath the centre of the foundation.

(5 marks)

iii) The following results were obtained from an oedometer test on a specimen of saturated clay

Applied Stress (kN/m2)

0 25 50 100 200 400 800

Void Ratio 0.985 0.950 0.921 0.880 0.833 0.784 0.737

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

35kN/m2 to 140kN/m2. (6 marks)

b) Calculate the consolidation settlement for a 6m thick layer of this clay, when

the effective stress changes from 35kN/m2 to 140kN/m2. (3 marks)

Total 20 marks



Figure Q6a



Fig Q6b



Question 7

i) Explain the difference between ‘compaction’ and ‘consolidation’ using geotechnical terminology. You should in your explanation refer to void ratio, pore water pressure, total stress, effective stress and soil mineralogy along with any other parameters you deem relevant.

(6 marks)

ii) 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 14m below ground level. The water table is located at a depth of 5m below ground level within an 8m thick deposit of sandy gravel overlying 6m of clay.

(14 marks)

Total 20 marks



Sandy Gravel Bulk Unit Weight = 18kN/m3 5m Saturated Unit Weight = 20kN/m3

Water Table

3m Clay

Bulk Unit Weight = 19kN/m3 6m Saturated Unit Weight = 21kN/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 ) / d

2

END OF PAPER

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TW58 UNIVERSITY OF BOLTON SCHOOL OF ENGINEERING BENG (HONS) CIVIL ENGINEERING SEMESTER ... · 2017-10-10 · Page 4 of 17 School of Engineering BEng (Hons) Civil Engineering Semester