Islamic University of Gaza

2nd

semester 2013/2014

Faculty of Engineering Instructors: Prof. Mohammed Awad

Civil Engineering department Dr. Jehad Hamad

Soil Mechanics ECIV 3351 T.A: Engr. Othman Tayeh

Engr. Samia Nassar

1

Q. No Maximum

mark Mark Notes

1 10

2 10

3 20

4 20

5 20

Total 80

Student Name ID

Soil Mechanics ECIV 3351

Time Allowed: 75 minutes

Mid-Term Exam 12/4/2014

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SHOW ALL WORK! This is close book exam: please enter answers with appropriate units. Partial

credit will not be given unless steps are shown. Correct answers must have supporting calculation.

All assumptions should be cited.

Write answer logically, neatly, and legibly

Question (1): (10 points)

The moist unit weight of a soil sample is 16.5KN/m3. Given that the w=15%

and Gs=2.7, find:

a) Dry unit weight (ɤd).

b) The porosity (n).

c) The degree of saturation (S).

d) The mass of water in Kg/m3 that must be added to reach full saturation.

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Question (2): (10 points)

a) Show the saturation moisture content is

wsat=

)

where

b) A geotechnical laboratory reported these results of five samples taken from a

single boring. Determine which are not correctly reported, if any, show your

work: where

Sample #1: w=30%, ɤd=14.9 KN/m3, ɤs=27 KN/m3,clay.

Sample #2: w=20%, ɤd=18 KN/m3, ɤs=27 KN/m3,silt.

Sample #3: w=10%, ɤd=16 KN/m3, ɤs=26 KN/m3,sand.

Sample #4: w=22%, ɤd=17.3 KN/m3, ɤs=28 KN/m3,silt.

Sample #5: w=22%, ɤd=18 KN/m3, ɤs=27 KN/m3,silt.

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Question (3): (20 points)

Classify the following soils (a & b) using the unified soil classification system.

(Give group Symbol & group Name).

a) A clayey soil sample weights 1.5 N. Its clay fraction 0.34, gravel fraction

0.15, sand fraction 0.2, silt fraction 0.31. If its liquid limit is 60%, and its

plastic limit is 26%.

b) The particle size distribution for a soil sample shown in the table below,

with LL=30% and PL=18%

Particle

size (mm)

% Finer

than

6 100

4.75 95

2.36 84

1.3 60

0.6 30

0.2 10

0.075 8

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Question (4): (20 points)

For the Figure shown below;

1.Find the Pressure head at the following points A – B – C – D – E.

Assume 2.5k1 = k2 = 1.5 k3 = 2k4=3 k5

2. Find the flow rate.

(Hint k1 = 3.5*10-2

cm/sec)

6 cm 5 cm 5 cm 5 cm

Soil 1

K1 Soil 2

K2

Soil 3

K3

Soil 4

K4 Soil 5

K5

Wat

er

Wat

er

B A C D

E

25 cm

17 cm

1.5 cm

1.5 cm

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Question (5): (20 points) For the flow net shown below, if the coefficient of permeability of the soil below the

dam is (5.2x10-3

cm/sec) and ɤsat = 18.2 kN/m3, find the following:

A- The rate of seepage (m3/sec /m).

B- The uplift force underneath the dam.

C- The effective stress at points L and N.

D- The driving head at point M.

10 m

8

m 8

m

1 m

6 m

30 m

Water table

Water table

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Useful formulas

)...(1

,

...

21)(

2

2

1

1

)( 21 nHHHeqH

n

n

eqH HkHkHkH

k

k

H

k

H

k

H

Hk

n

S.e=Gs w q= k i A

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