OCD27 UNIVERSITY OF BOLTON WESTERN INTERNATIONAL COLLEGE FZE BENG (HONS) CIVIL ENGINEERING SEMESTER TWO EXAMINATION 2016/2017 GROUND AND WATER STUDIES 2 MODULE NO: CIE5005 Date: Saturday 27 May 2017 Time: 10.00 am to 1.00pm INSTRUCTIONS TO CANDIDATES: There are SIX questions on this paper. Answer any FIVE questions. Answer SECTION A and SECTION B on separate answer books. All questions carry equal marks. Marks for parts of questions are shown in brackets. This examination paper carries a total of 100 marks. Formula sheet/supplementary information is provided at the end of each section. All working must be shown. A numerical solution to a question obtained by programming an electronic calculator will not be accepted.
Page 2 of 18 SECTION A Question 1 (a) The triaxial compression test is the most widely used shear strength test for soils; the consolidated-drained triaxial test being the slowest among the different types. A consolidated-drained triaxial compression test carried out on three specimens (each 38mm in diameter and 76mm long) of the same soil yielded the following results : Test number 1 2 3 Cell Pressure (kpa) 100 200 300 Deviator stress at failure (kpa) 210 438 644 Draw the shear strength envelope on the Graph (Figure Q1a) provided on page 1 and determine the peak strength parameters with respect to effective stress, c and Φ, assuming that the pore pressure remains constant during the axial loading stage. (10 marks) Question 1 is continued over to the next page
Page 3 of 18 Question 1 continued Candidate Number 600 Shear Stress (kn/m²) 500 400 300 200 100 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 Normal Stress (kn/m²) FIGURE Q1a PLEASE ATTACH THIS SHEET TO YOUR ANSWER BOOKLET Question 1 is continued over to the next page
Question 1 continued Page 4 of 18 (b) On a certain site a surface layer of silty sand is 5m thick and overlies a layer of peaty clay 4m thick, which in turn is underlain by impermeable rock. Draw the effective and total stress profiles for the following conditions: (i) Water table at the surface as shown in FigureQ1b. (5 marks) (ii) Water table at a depth of 2.5m from the ground level within the layer of the silty sand (5 marks) FIGURE Q1b Total 20 marks Please turn the page
Question 2 Page 5 of 18 (a) A flexible foundation of length 5m and breadth 3m is to exert a uniform load of 6.5MN. The foundation is to be constructed on the surface of a layer of soil of finite vertical extent of 12m with a bulk unit weight of 18kN/m 3. (i) (ii) Determine the immediate settlement under the centre and at the corner of the foundation if the undrained elastic soil stiffness (Eu) is assumed to be 16MN/m 2 (Use Figure Q2a) (7 marks) For the above foundation, determine the potential damage due to differential settlement (3 marks) (b) Shear stresses in a soil mass are only produced when shear strains can occur. As the shear stress is applied the soil structure distorts. Sketch out the typical stress-strain curves for different soils. State why the maximum shear stress is not considered the soil shear strength during foundation design. Indicate the following points on the curves and define them: (i) Yield point (ii) Peak shear strength (iii) Ultimate strength (iv) Critical state strength (v) Residual Strength (10 marks) Total 20 marks Q2 continued over the next page
Page 6 of 18 Question 2 continued Figure Q2a. Influence values for immediate settlement Total 20 marks Please turn the page for supplementary information for SECTION A
Formula Sheet Page 7 of 18 END OF SECTION A Please turn the page for Section B
Page 8 of 18 Western International College FZE SECTION B Question 3. (a) Using flow balancing method, determine the approximate distribution of flow in the pipe network system A shown in Figure.Q3. (a) Using the information given in Table Q3-1, i. Make a sensible first estimate for the head at the pipe junction J in System A. Briefly explain the reasons for your selections. (3 marks) ii. Ascertain a first estimate of the level of error in your initial assumption using Table Q3-2 attached. Explain how you have determined the errors and what the errors mean. Candidates should complete Table Q3-2 attached and hand in with the answer. HRS tables are provided. (12 marks) Figure Q3.(a )Pipe Network system A Question 3 continued over the Page
Question 3 continued. Reservoir Water Level m AOD Page 9 of 18 Table Q3-1 Pipe Diameter (mm) Length (m) Ks(mm) A 100 A-J 300 900 1.5 B 92 J-B 200 1000 1.5 C 80 J-C 225 1500 1.5 (b) A 300mm diameter concrete sewer (ks = 1.5mm) is required to deliver 88 litres/sec. Determine the minimum gradient at which the sewer should be laid for it not to be surcharged. Comment on the velocity of flow for the same (HRS Table is provided). (5 marks) Question 4. Total 20 marks (a) Propose a possible drainage system which can be adopted for a country with occasional heavy rain fall which will last only for afew days in a year. Outline its operational benefits and drawbacks as compared to other sewerage systems. (5 marks) (b) Details of an existing surface water sewer system are given in Table Q4-1 in Page 10. The pipes in the system have pipe roughness coefficient ks of 1.5mm and the time of entry for surface water is 3 minutes. Using the Rational method, complete Table Q4-2 provided and comment on the adequacy of system if it has to withstand a storm of 1 in 2 years return period. Rainfall Table and HRS tables are provided. (15 marks) Question 4 continued over the Page
Page 10 of 18 Question 4 continued Table Q4-1 Pipe Ref No Pipe Length, L (m) Pipe gradient (1 in ) Imp. Area (ha) Pipe dia. (mm) 1.00 52 45 0.07 150 1.01 42.5 31 0.21 225 2.00 105 31 0.1 100 2.01 115 59 0.15 250 1.02 85 67 0.05 275 Total 20 marks Question 5. (a) An old tuberculated water main in normal condition with a slight degree of attack, having a ks value of 1.5mm, has a diameter of 200 mm and is 750m in length. When the flow rate Q is 20 litres/sec, the pressure recorded at the inlet is 3 bar and the pressure recorded at the outlet is 1.5 bar. Using Barr's equation, determine the value for the Darcy friction factor, λ and then determine the frictional head loss across the pipeline. Also determine the difference in the pipe levels at the inlet and outlet. Take the coefficient of kinematic viscosity for water as 1.14 x 10-6 m 2 /sec. (12 marks) (b) Sketch out the general shape of the Moody diagram for flow through pipes and briefly explain the factors which affect the value of the Darcy friction factor λ in each of the zones. (8 marks) Total 20 marks Please turn the page
Page 11 of 18 Question 6. (a) A 300 mm diameter pipe 2340 m long is discharging to a distribution system and is connected with a reservoir whose surface is 36m above the discharging end of pipe. The pressure at the start of the distribution system is 3 bar. If for the last 1170 m, a second pipe of the same diameter and friction coefficient to be laid beside the first and connected to it, what would be the increase in the discharge? Take λ= 0.02. Neglect all minor losses and assume the frictional head loss remains the same across the first pipe. (14 marks) (b) A foul sewer, with pipe surface roughness coefficient, ks of 1.5mm, is to be designed to serve 1325 houses. For a housing occupancy of 3 persons per dwelling and water consumption of 200 litres/head/day, determine a suitable pipe diameter and gradient. Assume appropriate estimates for design factor and infiltration. Justify your assumptions. HRS tables are provided (6 marks) Total 20 marks END OF QUESTIONS Please turn the page for supplementary information for SECTION B
Formulae Sheet hf = So L Page 12 of 18 z v 2g P g v 2g P g 2 2 1 1 2 2 1 z2 hf Q = A v hf = L v 2 2 g d hf = L Q 2 12.1 d 5 Re = v d = v d 1 ks 2log 3.7d 5.1286 0. Re 89 Q = 2.78 Ap i Please turn the page
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Table Q3-2. Flow balancing 1 st estimate Hj = m Pipe hf across SO Q Pipe (m) (1 in) (litre/s) A B C Error in Q =.. l/s TO BE HANDED IN WITH ANSWER BOOK Candidates ID No... Please turn the page
Page 18 of 18 Western International College FZE Table Q4-2. 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) 1.00 52 45 0.07 150 1.01 42.5 31 0.21 225 2.00 105 31 0.1 100 2.01 115 59 0.15 250 1.02 85 67 0.05 275 TO BE HANDED IN WITH ANSWER BOOK END OF SECTION B END OF PAPER Candidates ID No...