Soil Mechanics ECIV 3351 Time Allowed: 75 minutes ... -...
Transcript of Soil Mechanics ECIV 3351 Time Allowed: 75 minutes ... -...
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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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