# Soil Mechanics Questions and Answers – Modified Proctor Test and Harvard Miniature Compaction Test

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This set of Soil Mechanics Questions & Answers for Exams focuses on “Modified Proctor Test and Harvard Miniature Compaction Test”.

1. The air voids line contains ___________
a) constant percentage air voids
b) water voids
c) varying percentage air voids
d) specific gravity of solids

Explanation: A line that shows the water content – dry density relation for the compacted soil containing a constant percentage air voids is known as air voids line.

2. The zero air voids line is also known as ___________
a) density line
b) saturation line
c) specific gravity line
d) unit weight line

Explanation: When the voids present in between the soil particles are completely filled by the moisture or the water, then it has no air entrapped in it or has no air voids. Therefore, the zero air voids line is also known as saturation line.

3. The theoretical maximum compaction for any given water content corresponds to ______
a) least specific gravity
b) maximum specific gravity
c) zero air void condition
d) only air voids present without the presence of water

Explanation: Compaction is a process by which the soil particles are artificially rearranged into a closer state. This arrangement reduces the voids ratio. When the voids present in between the soil particles are completely filled by the water, then it has no air voids. This zero air void condition, corresponds to the theoretical maximum compaction for any given water content.

4. The zero air void line shows the _________
a) dry density as a function of water content for soil containing no air voids
b) saturated density as a function of water content
c) partially saturated density as a function of water content
d) dry density as a function of specific gravity

Explanation: When the dry density is plotted as a function of water content, then for soil containing no air voids is represented by a line that is known as the zero air void line.

5. The zero air voids line is established by equation of __________
a) $$ρ_d=\frac{G}{1+wG}$$
b) $$ρ_d=\frac{Gρ_w}{wG}$$
c) $$ρ_d=\frac{ρ_w}{1+wG}$$
d) $$ρ_d=\frac{Gρ_w}{1+wG}$$

Explanation: The dry density in relation to the water content can be given by the equation,
$$ρ_d=\frac{Gρ_w}{1+wG},$$
where, ρd=dry mass density
ρw= mass density of water
G=specific gravity.
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6. For a line showing the relation between water content and dry density for a constant degree of saturation is __________
a) $$ρ_d=\frac{G}{1+wG}S$$
b) $$ρ_d=\frac{Gρ_w}{wG}S$$
c) $$ρ_d=\frac{ρ_w S}{1+wG}$$
d) $$ρ_d=\frac{Gρ_w}{1+\frac{wG}{S}}$$

Explanation: For a line showing the relation between water content and dry density for a constant degree of saturation is given by,
$$ρ_d=\frac{Gρ_w}{1+\frac{wG}{S}},$$
where, ρd=dry mass density
ρw= mass density of water
G=specific gravity
S=degree of saturation.

7. The Modified Proctor test was standardised by ____________
a) IS
b) AASHO
c) ASCE
d) CBR

Explanation: The Modified Proctor test was standardised by the American Association of State Highway Officials and the Modified Proctor test is also known as the AASHO test.

8. In Modified Proctor test the number of layers of the soil is compacted is ___________
a) 1
b) 2
c) 5
d) 3

Explanation: In Modified Proctor test the number of layers of the soil is compacted is five. While in Standard Proctor test the number of layers of the soil is compacted is three.

9. The weight of rammer in Modified proctor test is ______________
a) 4.5 kg
b) 2.5 kg
c) 18 lb
d) 22 lb

Explanation: In Standard Proctor test, the layers of the specimen are tested with a free fall of rammer of weight 2.5 kg or 5.5 lb. The test consists in compacting at various water contents. Whereas in Modified proctor test, the layers of the specimen are tested with a free fall of rammer of weight 4.5 kg or 10 lb.

10. The free fall height of rammer in Modified Proctor test is __________ inches.
a) 5
b) 12
c) 16
d) 18

Explanation: In Modified Proctor test, the layers of the specimen are tested with a free fall of rammer of weight 4.5 kg or 10 lb with the height of free fall being 18 inches. The free fall height of rammer in Standard Proctor test is 12 inches.

11. The Modified Proctor test curve of the water content – dry density curve lies __________ the SPT curve.
a) above
b) below
c) left side
d) right side

Explanation: The compactive energy given to the soil is more in the Modified Proctor test than the Standard Proctor test due to the weight of the rammer and the height of the free fall. The Modified Proctor test curve of the water content – dry density curve lies above the SPT curve.

12. The Modified Proctor test has its peak relatively towards ____________ in water content – dry density curve.
a) right
b) left
c) centre
d) near origin

Explanation: The compactive energy given to the soil is 27260 kg-cm per 1000 cm3 of soil for which the Modified Proctor test has its peak relatively towards left in water content – dry density curve.

13. For same soil, the effect of heavier compaction is in ________
a) increase in the maximum dry density
b) decrease in the maximum dry density
c) decrease in stability
d) decrease in strength

Explanation: For same soil, the effect of heavier compaction is in increase in the maximum dry density. Compaction reduces the voids ratio and hence there is decrease in the porosity. Due to this, the dry density of the soil sample is increased.

14. For same soil, the effect of heavier compaction is to ________
a) decrease the optimum water content
b) decrease in the maximum dry density
c) decrease in stability
d) decrease in strength

Explanation: Compaction reduces the voids ratio and hence there is decrease in the porosity. Hence, for same soil, the effect of heavier compaction is to decrease the optimum water content.

15. In Harvard miniature compaction test, the soil is compacted by _______
a) vibration
c) impact
d) dynamic

Explanation: In Harvard miniature compaction test, the soil is compacted by kneading action of a cylindrical tamping foot that has a diameter of 0.5 inch or 12.7 mm. The soil is compacted in small cylindrical mould.

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