1. The air content ratio is defined as the ratio of _____
a) volume of air voids to total volume of the soil mass
b) volume of air voids to volume of total voids
c) volume of air voids to volume of water
d) volume of voids to total volume of the soil mass
Discussion
Explanation: The air content is defined as the ratio of the volume of air voids to the volume of total voids. It is related with the degree of saturation S as ac=1-S.
2. For a perfectly dry sample, the degree of saturation is equal to zero.
a) True
b) False
Discussion
Explanation: For a perfectly dry, hence the degree of saturation is equal to zero. Sample the volume of water present is equal to zero. For a fully saturated sample, the degree of saturation is equal to one.
3. The degree of saturation is defined as the ratio of _____
a) volume of water to total volume of voids
b) volume of air voids to volume of total voids
c) volume of air voids to volume of water
d) volume of voids to total volume of the soil mass
Discussion
Explanation: In a soil sample, some space is occupied by water and the rest by air. The degree of saturation is defined as the ratio of the volume of water to the total volume of voids.
4. The relationship between porosity n and void ratio e is given by _______
a) 1+n= 1/(1+e)
b) 1-n= 1/(1+e)
c) n= 1/e
d) n= 1/(1+e)
Discussion
Explanation: The porosity n and void ratio e are given by,
e = Vv/Vs = n/(1+n)
n= Vv/V = e/(1+e)
n= e*(1-n)
So, 1-n=1/(1+e).
5. The range of degree of saturation is between 0 and 0.25 for a humid soil sample.
a) True
b) False
Discussion
Explanation: The range of degree of saturation is between 0 to 0.25 for humid, 0.25 to 0.5 for damp, 0.5 to 0.75 for moist and 0.75 to 1 for wet soil sample.
6. What will be the degree of saturation of a soil sample whose specific gravity G=2.7, void ratio e=0.66 and water content w=20%?
a) 85.88%
b) 90.91%
c) 81.81%
d) 92.92%
Discussion
Explanation: Given,
G=2.7
e=0.66
w=20%=0.2
Since the degree of saturation is S=wG/e
S=(0.2*2.7)/0.66
S=0.8181
In percentage S=81.81%.
7. In wet soil mass, air occupies one-seventh of its volume and water occupies one- eighth of its volume. The void ratio of the soil is ______
a) 0.25
b) 0.36
c) 0.43
d) 1
Discussion
Explanation: Given,
Volume of water Va= (1/7) total volume V
Volume of water VW= (1/8) total volume V
Void ratio e= Vv/VS
Vv= Va + VW
Vv=(1/7)+(1/8)
Vv=(15/56)=0.268
VS= V-Vv
VS=1-0.268=0.732
e= 0.268/0.732
e=0.36.
8. The term density index ID is used for cohesion-less soil only
a) True
b) False
Discussion
Explanation: The term density index ID is not applicable to cohesive soil because of uncertainties in the laboratory determination of the voids ratio in the loosest state of the soil (emax).
9. The formula for density index ID is ______
a) (emax – e)
b) \(\frac{(e_{max} – e)}{(e_{min}-e)}\)
c) \(\frac{(e_{max} – e_{min})}{(e_{max}-e)}\)
d) \(\frac{(e_{max} – e)}{(e_{max}-e_{min})}\)
Discussion
Explanation: The density index is defined as the difference between the voids ratio of the soil in its loosest state emax and its natural void ratio e to the difference between the voids ratio in the loosest and densest state.
ID=\(\frac{(e_{max} – e)}{(e_{max}-e_{min})}\).
10. When the natural state of cohesion-less soil is in its loosest form, its density index ID is equal to ____
a) 0
b) 0.5
c) 1
d) 1.5
Discussion
Explanation: Cohesion-less soil is in its loosest form will have its void ratio e=emax.
Since ID=\(\frac{(e_{max} – e)}{(e_{max}-e_{min})}\)
ID=\(\frac{(e_{max} – e_{max})}{(e_{max}-e_{min})}\)
ID=0.