Geotechnical Engineering MCQ Unit 1 | Basic Civil Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Geotechnical Engineering”.

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                                                               UNIT - 1


1. A soil mass in a three-phase system consists of ______
a) solids, water and air
b) sand, gravel and air
c) solids and water only
d) solids and air only
View Answer

Answer: a

Explanation: Solids and water, solids and air are two-phase systems. Sand, gravel and air are not the phases. Solids, water and air are considered to be a three-phase system of the soil mass.



2. When the soil is fully saturated, then there are no air voids present in it.
a) True
b) False
View Answer

Answer: a

Explanation: The air voids get filled with water leaving no air voids when the soil is fully saturated. When the soil is completely dry, then the soil will contain only air voids.



3. The volume of voids Vv is equal to the sum of ______
a) the volume of air and volume of solids
b) the volume of air and volume of water
c) the volume of water and volume of solids
d) the volume of water and the weight of water
View Answer

Answer: b
Explanation: The voids in soil mass are occupied by air and water. Hence, the volume of voids equals to the volume of air and volume of water.



4. The phase diagram is also known as _______
a) soil grain diagram
b) block diagram
c) constituents diagram
d) element diagram
View Answer

Answer: b
Explanation: It is always convenient to show the constituents occupying separate spaces as blocks. In the phase diagram, the soil occupies the bottom position. Water and air occupy the middle and top positions.



5. The weight of total voids is equal to the weight of Water.
a) True
b) False
View Answer



6. In the phase diagram, volumes are represented on the ________
a) left side
b) right side
c) top
d) bottom
View Answer

Answer: a
Explanation: Volumes are represented on the left side whereas weights are represented on the right side of the block diagram.



7. The volume of solids is represented as _______ in the phase diagram.
a) Vv
b) VW
c) VS
d) Va
View Answer

Answer: c
Explanation: The volume of voids, water and air are represented as Vv, VW and Va. The volume of solids is represented as Vd or VS in the phase diagram.



8. The weight of solids is represented as _______
a) Wd
b) WW
c) Wa
d) W
View Answer

Answer: a
Explanation: The weights of Water, air and total weight are represented as WW, Wa and W. The weight of solids is represented as Wd or WS in the phase diagram.



9. The total weight of the moist sample is the sum of _______
a) WW+Wd
b) Wa+WW
c) Wa+Wd
d) Wv
View Answer

Answer: a
Explanation: The sum of the weight of voids Wv and weight of solid is the total weight. The weight of total voids is equal to the weight of Water and weight of air. Since the weight of air is considered to be negligible, the weight of total voids is equal to the weight of Water. Therefore, the total weight of the moist sample is the sum of WW+Wd.



10. For a fully saturated soil sample, the volume of voids is equal to _______
a) volume of air
b) volume of water
c) the volume of air and volume of water
d) the volume of water and volume of solids
View Answer

Answer: b
Explanation: In a fully saturated sample, the volume of voids gets completely filled by water leaving no air voids present in the sample. Hence, volume of voids equals the volume of water.



11. A soil sample weighs 190kN. After oven drying it weighs 150kN. What will be the weight of Water before oven drying?
a) 35 kN
b) 40 kN
c) 30 kN
d) 45 kN
View Answer

Answer: b
Explanation: Given,
Weight of soil sample W=190kN
Weight after oven drying Wd=150kN
Weight of Water WW=W-Wd
WW=190-150
WW=40kN.



12. In wet soil mass, air occupies one-seventh of its volume and Water occupies one- eighth of its volume. What will be the ratio of volume of voids with respect to the total volume?
a) 0.329
b) 0.279
c) 0.432
d) 0.286
View Answer

Answer: d
Explanation: Given,
Volume of Water Va= (1/7) total volume V
Volume of Water VW= (1/8) total volume V
Volume of voids Vv= Va + VW
Vv=(1/7)V+(1/8)V
Vv=(15/56)V=0.268V.

This set of Soil Mechanics Interview Questions and Answers for Experienced people focuses on “Void Ratio, Porosity and Degree of Saturation”.


1. What will be the porosity of a soil sample whose void ratio is 0.35?
a) 19.5%
b) 40.65%
c) 25.9%
d) 30%
View Answer

Answer: c
Explanation: Given,
Void ratio e=0.35
Porosity n=e1+e
n=0.351+0.35
n=0.351.35
n=0.259
In percentage n=25.9%.



2. ______ is independent of the total volume of the soil mass.
a) Bulk unit weight
b) Dry unit weight
c) Submerged unit weight
d) Unit weight of solids
View Answer

Answer: d
Explanation: The unit weight of solids is a function of the volume of solids, which does not change with water or moisture content. Whereas, bulk, dry and submerged unit weights are functions of total volume.



3. Void ratio is the ratio of _____
a) volume of voids to total volume
b) volume of voids to volume of solids
c) volume of solids to volume of voids
d) volume of soil mass to volume of voids
View Answer

Answer: b
Explanation: The volume of voids to the volume of solids is void ratio. The volume of voids to total volume is porosity. The volume of voids includes the volume of air voids as well as the volume of water present.



4. If the porosity of a soil sample is 22%, then what will be its void ratio?
a) 0.3
b) 0.27
c) 0.28
d) 0.25
View Answer

Answer: c
Explanation: Given,
Porosity n= 22%= 0.22
Void ratio e = n/(1-n)
e= 0.22/(1-0.22)
e= 0.28



5. For a soil sample, the ratio of saturated unit weight to dry unit weight is equal to 1.2 and specific gravity of solids G is 2.65, then its void ratio will be _____
a) 0.58
b) 0.66
c) 0.53
d) 0.94
View Answer

Answer: b
Explanation: Given,
The ratio of saturated unit weight to dry unit weight is equal to 1.2
γsat/γd= 1.2
Specific gravity of solids G is 2.65
γsat = (G+e)1+eγwandγd=G1+eγw
→ γsat/γd= (G+e)1+eγw/G1+eγw
γsat/γd = (G+e) / e
→(G+e) / e = 1.2
e = 1.2*G – G
e = 1.2*2.65 – 2.65
e = 0.53.




6. For a fully saturated soil sample, the degree of saturation is ______
a) 0
b) 0.5
c) 0.8
d) 1
View Answer

Answer: d
Explanation: For a fully saturated soil sample, the volume of water is equal to the volume of voids and hence the degree of saturation is equal to one.



7. The percentage void 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
View Answer

Answer: a
Explanation: The percentage void ratio is defined as the ratio of the volume of air voids to the total volume of the soil mass. It is expressed as percentage. na = (Va/v) * 100.



8. If air content and degree of saturation are represented as ac and S respectively, then the relationship between them is ________
a) ac= 1/S
b) ac=1-S
c) S=1+ac
d) S=ac
View Answer

Answer: b
Explanation: Air content is the ratio of the volume of air voids (Va) to the volume of voids (Vv). The degree of saturation (S) is the ratio of the volume of water (VW) to the volume of voids (Vv) in a given soil mass.
ac=Va/Vv
S=VW/Vv
Since Va=Vv-VW
ac=1-VW/Vv
ac=1-S.



9. 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
View Answer

Answer: b
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. ac= Va/Vv.



10. For a perfectly dry sample, the degree of saturation is equal to zero.
a) True
b) False
View Answer

Answer: a
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.



11. 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
View Answer

Answer: a
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.



12. 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)
View Answer

Answer: b
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)
∴ 1-n=1/(1+e).



13. The range of degree of saturation is between 0 and 0.25 for a humid soil sample.
a) True
b) False
View Answer

Answer: a
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.



14. 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%
View Answer

Answer: c
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%.



15. 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
View Answer

Answer: b
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.




This set of Basic Civil Engineering Multiple Choice Questions & Answers (MCQs) focuses on  “Geotechnical Engineering”.


1. Water content is given by:
a) Weight of water/mass of soil
b) Mass of water/mass of solid
c) Mass of water/mass of soil
d) Mass of water/weight of solid
View Answer

Answer: b
Explanation: In Geotechnical Engineering, water content is an important parameter for analysing the soil. It is expressed as mass of water divided by mass of solids. It is denoted by w and expressed in %.



2. Who is the father of Geotechnical Engineering?
a) Christian Otto Mohr
b) Clausius Cleyperon
c) John Smith
d) Karl Von Terzaghi
View Answer

Answer: d
Explanation: He was an Austrian civil engineer and geologist. Most of the findings in geotechnical engineering and soil properties are done by him.



3. According to Darcy’s Law:
a) q=iA
b) q=kA
c) q∞iA
d) q∞kA
View Answer



4. Triaxial compression test is used to find __________ of soil.
a) Compressive strength
b) Permeability
c) Specific gravity
d) Shear strength
View Answer



5. ____________ index is used to find settlement of soil.
a) Compression
b) Expansion
c) Recompression
d) Reloading
View Answer

Answer: a
Explanation: A plot is made between void ratio (e) and log effective stress (logσ). It shows different curves corresponding to loading, unloading and reloading of soil. Compression index Cc= – ∆e⁄∆logσ





6. Which of the following does not happen when compaction is done?
a) Permeability decreases
b) Water content increases
c) Shear strength decreases
d) Compressibility decreases



7. ____________ is the measure of loss of strength with remoulding, with water content unchanged.
a) Compressibility
b) Sensitivity
c) Stability
d) Thixotropy



8. In Geotechnical Engineering, soil is considered as a _________ phase material.
a) 3
b) 2
c) 1
d) 4
View Answer

Answer: a
Explanation: Soil is a 3 phase material. It consists of solids, water and air voids. It is represented in a 3 phase diagram with volume on left side and mass on the right side.



9. Fine particles are those particles with size less than _______ mm diameter.
a) 0.023
b) 0.090
c) 0.075
d) 4.75



10. The mass density of water at 4oC is:
a) 1000g/ml
b) 1kg/m3
c) 1000Mg/m3
d) 1000kg/m3
View Answer

Answer: d

Explanation: Mass density is the ratio of mass of water to volume of water. At 4oC, it is 1g/ml or 1000kg/m3 or 1Mg/m3.



11. Percentage air voids is denoted as:
a) v
b) na
c) s
d) av
View Answer

Answer: b
Explanation: Percentage air voids are the ratio of volume of air in voids to total volume of soil. It is denoted by na and expressed as a %.



12. Porosity and void ratio are related by:
a) e = n⁄(1-n)
b) n = e⁄(1-e)
c) 1-e = n
d) (1+n)⁄n = e-1
View Answer

Location: India

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