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Islamic University of Gaza Faculty of Engineering Engineeri ng
2 semester 20 13/2014 Instructors: Prof. Mohammed Awad Dr. Jehad Hamad T.A: Engr. Othman Tayeh Engr. Samia Nassar
Civil Engineering department
Soil Mechanics ECIV 3351
Soil Mechanics ECIV 3351 Time Allowed: 75 minutes Mid-Term Exam 12/4/2014
Student Name
Q. No
Maximum mark
1
10
2
10
3
20
4
20
5
20
Total
80
ID
Mark
1
Notes
Mid-Term Exam
Soil Mechanics ECIV 3351
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) 3 The moist unit weight of a soil sample is 16.5KN/m . 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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Mid-Term Exam
Soil Mechanics ECIV 3351
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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Mid-Term Exam
Soil Mechanics ECIV 3351
Question (3): (20 points) Classify the following soils (a & b) using the unified soil s oil 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 is 26%.
b) The particle size distribution for a soil sample shown in the table below, with LL=30% and PL=18% Particle % Finer size (mm) 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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Mid-Term Exam
Soil Mechanics ECIV 3351
Question (4): (20 points) For the Figure shown below; 1.Find the Pressure head at the following points A – B B – C C – D D – E. E. Assume 2.5k 1 = k 2 = 1.5 k 3 = 2k 4=3 k 5 2. Find the flow rate. -2 (Hint k 1 = 3.5*10 cm/sec)
1 7 c m
6 cm
r e t a W E
Soil 5 K5
5 cm
5 cm
Soil 3 D K3
C
Soil 4 K4
5
Soil 2 K2
5 cm
Soil 1 B K1
r e t a W
A
2 5 c m
1.5 cm 1.5 cm
Mid-Term Exam
Soil Mechanics ECIV 3351
Question (5): (20 points) For the flow net shown below, if the coefficient of permeability per meability of the soil below the dam is (5.2x10-3 cm/sec) and ɤsat = 18.2 kN/m3, find the following: 3
A- The rate of seepage (m /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. 30 m Water table
m 0 1
Water table 1m
m 8
6m
m 8
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Mid-Term Exam
Soil Mechanics ECIV 3351
Useful formulas k H ( eq )
H
H H 1 H 2 ... n k 1 k 2 k n
S.e=Gs w
, k H ( eq )
1 H
(k H 1 H 1 k H 2 H 2 ... k H n H n )
q= k i A
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