4. The total exam value is I 00 marks

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1 PROFESSIONAL ENGINEERS ONTARIO NATIONAL :EXAMINATIONS -May CIV-A4 GEOTECHNICAL MATERIALS AND ANALYSIS 3 HOURS DURATION NOTES: 1. This is a closed book examination. 2. Read all questions carefully before you answer 3. Should you have any doubt regarding the interpretation of a question, you are encouraged to complete the question submitting a clear statement of your assumptions. 4. The total exam value is I 00 marks 5. One of two calculators can be used: Casio or Sharp approved models. 6. Drawing instruments are required. 7. All required charts and equations are provided at the back of the examination. 8. YOU MUST RETUR.i~ ALL EXAMINATION SHEETS.

$reasons to JUSTIFY THE STATEMENT IN YOUR ANS\VER BOOK.$ $(i) A uniformly graded soil has a good and equal representation of all pa1ticle sizes from the largest to smallest size of that particular group T F (ii) T F Seepage"" q-= kl\., (;;) (wldf~).$

2 NATIONAL EXAMINATIONS -Mav CIV-A4 GEOTECHNICAL MATERIALS AND ANALYSIS Question 1: ANSWER ALL QUESTIONS (4 x 5 == 20 marks) State the correct answer for each of the questions below and provide reasons to JUSTIFY THE STATEMENT IN YOUR ANS\VER BOOK. (i) A uniformly graded soil has a good and equal representation of all pa1ticle sizes from the largest to smallest size of that particular group T F (ii) T F Seepage"" q-= kl\., (;;) (wldf~). Figure 1 The seepage below the dam using the flow net and the other information shown in Figure 1 is equal to 3 m 3 /day perm width. (iii) The pore-water pressure in an over consolidated clay is negative when it is subjected to a loading that is less tltan its preconsolidation pressure. T F (iv) The degree of saturation of both compacted sand and clay specimen at optimum moisture content is always lower than 100%. T F (v) Both the triaxial test and the direct shear test equipment can be used to determine the effective shear strength parameters ( c' and ~ ') of sands and as well as clays under drained loading conditions (i.e. CD tests). T F 2

3 NATIONAL EXAMINATIONS-May CIV-A4 GEOTECHNICAL MATERIALS AND ANALYSIS Q uestion 2: (10 marks) Rriefly explain the three different "limit,, lateral earth pressures (i.e., at-rest, active, and passive conditions) that can act on a retaining wall. Also, show the Mohr circle for each condition (Note: You arc expected to draw simple sketches of retaining walls and Mohr failure envelopes for the lhree cases; Fignre 2 is shown below as an example without providing the key details). f Figure 2 Question 3: (10 marks) As a junior engineer, you are asked to estimate the settlement that would arise due to the construction of a structure on a soil that predominantly has organic material such as peat. What test or tests do you unde11akc? What are the key properties or parameters would you derived from these tests. Also, how would you proceed with your analysis for estimating the settlement? Question 4: (Value: 20 marks) Figure 3 shows the plan view of a 5 story condominium structure. Determine the increase in vertical stress Acrz due to the load, at depths of 2 and S m vertically below point A (Use superposition method). Comment on the stress values determined at different depths and how this information is useful for a geotechnical engineer. The load on foundation of the building (.shaded area) will be approximately equal to l 0 kpa per story. 3

4 NATIONAL F:XAMINATIONS-May CIV-A4 GEOTECHNICAL MATERIALS AND ANALYSIS -~ 10ml-50m-fl f 50m r x ai ah ag af ae ad Figure 3 Question 5: For a cutoff wall shown in Figure 4 (Value: 20 marks) a. Establish the flow nets (i.e. flow and equipotential lines) following alj the rules (draw on Figure 4). (10 marks) b. Calculate the effective stress at point A (back of the piling) (r.a1 = 20 kn/m 3 ). (10 marks) Effective stress ( u' ) = Total stress ( u ) - Pore water pressure ( u) u=(h - z)rw 4

5 NATIONAL EXAMINATIONS -May ClV-A4 GEOTECHNICAL MATERIALS AND ANALYSIS r 3m 3m A l1m r 2m l 3m L k = 2.0 x 10 5 m/s IMPERMEABLE LA YER Figure 4 Question 6: (Value: 20 marks) A series of drained triaxial tests was carried out on specimens of a sand prepared at the same porosity and the following results were obtained at failure. All-round pressure (kn/m 2 ) 100 I 200 I 400 l 800 l Principal stress difference (kn/m 2 ) 452 I 908 l 1810 l 3624 l Determine the value of the angle of shearing resistance 'analytically and also draw the Mohr circles to verify your result. 5

6 NATIONAL EXAMINATIONS-Mav CIV-A4 GEOTECHNICAL MATElUALS AND ANALYSIS 6

7 NATIONAL EXAMINATIONS-May CIV-A4 GEOTECIINICAL MATERIALS AND ANALYSIS 7

8 NATIONAL EXAMINATIONS - May ~CIV-A4 GROTECHNICAL MATERIALS AND ANALYSIS - ~ q./ z,,,,-- x JP o.2s x , ~ 0 28 I I m.= _..., I o m =., m = oo I tt::+:t:b1-:'~m~*ef rr 1.8~ ~::; - - m = 3.o 0.24,A ~ _ 0.24 m = l.s Q.18 1 I LJ.J,... Q 18 0,01 0, v / /.m = 0.7 II Iv./ I I I I I 0.16 ~--+--t f mjv "' 1"'1-' ->'/c; +--t-m ""' 0.6.._ 0.16 ' z Oz Load q 0 x per unit of area y m=-z;n = z- m and n are interchangeable #'. ~-- 'wr:...--m = 1.2,_ 0.22 ~v ~'='rb -- ~~, :~ m"' 0.9.._ , /~f'-~-t--". t;n = Q.8 '"" I/...- I l I , H~ 1 J~I/ v,,.- _J,.,-'-+++~.---m = 1.4 m ::: Value of n 8

9 NATIONAL EXAMINATIONS -May CIV-A4 GEOTECIINICAL MATRRIALS AND ANALYSIS Depth scale 9

10 NATIONAL EXAMINATIONS - May CIV-A4 GEOTECHNICAL MATERIALS AND ANALYSIS G = Ps s P.. a = yd P='LN'+uA P IN' - =--+u A. A o-=a-'+u (or) o-'=cy-u For a.fully submerged soil ()' = y' D (i'ormula Sheet r (Se+G.J rw l 1-e wg.,,.., Se v = ki; where i = h/l; q = kia; N q = k-h.., f_(width) ; Nd h = n" h P N w d Boussinesq 's equation for detennining vertical stress due to a point load 5i 2 3Q a =--' z 2;r z2 ( )2 1+ ;. Determination of vertical stress due to a re<.:tangular loading: az =q le (Charts ajso available) m = Biz and n :::: Liz (both m and narc interchangeable) Approximate method to determine vertical stress, er z = ( q ~t ) B + z L +z Equation for dctcnnination vertical stress using Newmark's chart: a z = N q r f =c' + (a--uw )tan~'; a- 1 ' =a- 0 3 tan 2 ( 45 + ~' ) + 2c'tan( 45 + ~' ) 1 ( ' t ) Mohr's circles can be represented as stress points by plotting the data - \CY 1 - a ( ),t.,1 -I ( '). d 1 Q against - \a- 1 +a 3 ; r =sm tan a an c =-- 2 cos ' 6.e 1 +e C a'1 6.e ( 1 ) 1 ( e - e1 ] - =- -o ; s~ =ll-c-log-. ; Sc =µsod; m1,=-- --, =---.a. tiff H 0 l+e 0 a 0 l+e 6.o- 1+e ao 10

11 NATIONAL EXAMINATIONS -May CIV-A4 GEOTECIINICAL MATERIALS AND ANALYSIS I lab (field dlah 2 = ( H field / 2 ) 2 T == c J T = n U 2 (for U < 60%) v d2 ' 4 T, == log (l - U) (for U > 60%) Cc e -e 0 (<T 1 ');also, Cc """' 0.009(LL -10); log - 1 o-o 11

Page 1 of 10. PROFESSIONAL ENGINEERS ONTARIO NATIONAL EXAMINATIONS Mav CIV-A4 GEOTECHNICAL MATERIALS AND ANALYSIS 3 HOURS DURATION

Page 1 of 10. PROFESSIONAL ENGINEERS ONTARIO NATIONAL EXAMINATIONS Mav CIV-A4 GEOTECHNICAL MATERIALS AND ANALYSIS 3 HOURS DURATION Page 1 of 10 PROFESSIONAL ENGINEERS ONTARIO NATIONAL EXAMINATIONS Mav 2015 3 HOURS DURATION NOTES: 1. This is a closed book examination. 2. Read all questions carefully before you answer 3. Should you