1. The minimum possible void ratio of uniformly graded spherical grains is _______
a) 0.20
b) 0.25
c) 0.30
d) 0.35
Discussion
Explanation: Consider a unit cube of soil having spherical particles of diameter d.
Volume of the solids Vs= (π/6)=0.5236
The total volume V=(1-cosα)*(√(1+2cosα))
Minimum void ratio is possible in densest state with α=60°
V=(1-cos60°)*(√(1+2cos60°))
V=0.7071
Volume of the voids Vv=V-Vs=0.7071-0.5236
Vv=0.1835
Voids ratio e= Vv/ Vs=0.1835/0.5236
e=0.35.
2. The volume if voids of a rhombohedral array of spherical grains with α=75° is _______
a) 0.4266
b) 0.7439
c) 0.3895
d) 0.3595
Discussion
Explanation: Given,
α=75°
The total volume V=(1-cosα)*(√(1+2cosα))
V=(1-cos75°)*(√(1+2cos75°))
V=0.9131
Volume of the solids Vs=(π/6)=0.5236
Volume of the voids Vv=V-Vs=0.9131-0.5236
Vv=0.3895.
3. The water content of a soil sample cannot be determined by _____ method.
a) oven drying
b) alcohol
c) calcium carbide
d) pipette
Discussion
Explanation: The pipette method is the standard sedimentation method used in laboratory for wet mechanical or sedimentation analysis.
4. In oven drying method, the soil sample is kept for about ______ hours in the oven.
a) 1
b) 2
c) 24
d) 48
Discussion
Explanation: For complete drying, sandy soil takes about 4 hours and fat clays take about 14 to 16 hours. To assure complete drying of sample, it is kept for about 24 hours.
5. An organic soil sample is kept in oven for its water content determination. The temperature preferred is ______
a) 60°
b) 80°
c) 105°
d) 110°
Discussion
Explanation: For organic soils like peat, a lower temperature of about 60° is preferable to prevent the oxidation of the organic matter.
6. ______ method is specially suited to a circumstance where water content is to be quickly determined for the purpose of proper field control.
a) Oven drying
b) Sand bath
c) Alcohol
d) Calcium carbide
Discussion
Explanation: Calcium carbide method is very quick as the result can be obtained in 5 – 10 minutes. The field kit contains the moisture tester, a small single – pan weighing balance, a bottle containing calcium carbide and a brush.
7. In pycnometer method of water content determination, it is necessary to accurately know the specific gravity G of soil whose water content is to be determined.
a) True
b) False
Discussion
Explanation: In pycnometer method, the water content is calculated from,
\(w=[(\frac{M_2-M_1}{M_3-M_4})*(\frac{G-1}{G})- 1]× 100\)
Where, M1=Empty mass of pycnometer with cap
M2= mass of pycnometer + 200g to 400g of soil sample
M3= mass of pycnometer +soil sample + water till hole of conical cap
M4= mass of pycnometer + water till hole of conical cap
G=Specific gravity.
8. An oven – dried soil of mass 400g is placed in a pycnometer where empty weight is 573g. The mass of pycnometer with soil is 973g. The total mass of pycnometer with water and soil inside is 1605g. The pycnometer filled with water alone has mass of 1480. The specific gravity of solids is 2.65. Its water content is ______
a) 40.456
b) 46.504
c) 23.236
d) 6.423
Discussion
Explanation: M1= 573
M2=973
M3=1605
M4=1480
G=2.65
\(w=[(\frac{M_2-M_1}{M_3-M_4})*(\frac{G-1}{G})- 1]× 100 \)
\(w=[(\frac{973-573}{1605-1480})*(\frac{2.65-1}{2.65})- 1]× 100 \)
=46.504%.
9. In calcium carbide method, the gas produced is______
a) methane
b) carbon dioxide
c) acetylene
d) oxygen
Discussion
Explanation: The acetylene gas is produced by the reaction of moisture of soil and the calcium carbide. The gas exerts pressure on a sensitive diaphragm attached to a dial gauge which reads the water content.
10. The water content of soil deposit in the in-situ condition is determinate by ______ method.
a) radiation
b) pycnometer
c) calcium carbide
d) oven – dry
Discussion
Explanation: The radiation method consists of 2 steel casings. A device containing some radio–active isotope is lowered in one caning and a detector in another. The neutrons emitted by the device are detected by the detector and the loss of energy of neutrons is equated to the water content.