Compaction of Soil MCQs – Part 1

11 questions. Tap an option to check it instantly, then read the solution.

Practice SSC JE and other civil engineering exam questions on soil compaction: Proctor tests, optimum moisture content, maximum dry density, zero air voids, compaction energy and field rollers. Tap an option to check it, then open the full explanation for each question.

Question 1Medium

In compaction test 1, a 10 kg hammer falls 500 mm on each of 3 layers with 25 blows per layer. In compaction test 2, a 5 kg hammer falls 250 mm on each of 6 layers with 25 blows per layer. If the same mould is used, what is the ratio of the compaction energy of test 1 to that of test 2?

Full explanation

Answer: C. 2

E ∝ W·h·n·N. E₁ = 10×0.5×3×25 = 375; E₂ = 5×0.25×6×25 = 187.5; E₁/E₂ = 2.

Question 2Easy

Identify the behaviour study of soils in which the zero air void unit weight is found.

Full explanation

Answer: A. Compaction test

The zero-air-voids (100% saturation) line is plotted with the compaction curve in the Proctor compaction test.

Question 3Easy

For field compaction of cohesive soil, the combination of tamping action and kneading action on the soil is achieved by:

Full explanation

Answer: B. sheep foot rollers

Sheep-foot rollers have projecting feet that tamp and knead clay; they are the standard choice for cohesive soils.

Question 4Easy

Proctor compaction test is made to determine the moisture content at which soil will be compacted to obtain ______.

Full explanation

Answer: C. maximum dry density

The Proctor test finds the optimum moisture content (OMC) at which the soil reaches its maximum dry density.

Question 5Medium

The dry density decreases in cohesionless soil with an increase in water content due to which of the following reasons?

Full explanation

Answer: B. Bulking of sand

At low water contents, thin water films and surface tension hold sand grains apart (bulking), so the volume rises and dry density falls.

Question 6Easy

After compacting the subgrade by suitable methods, the tests to ensure that the desired compaction has been achieved is/are:

Full explanation

Answer: D. moisture content and field density determination test

Field compaction is checked by measuring in-situ dry density and water content and comparing with the laboratory MDD (relative compaction).

Question 7Easy

The optimum water content (OWC) is the moisture content at which the soil attains ______.

Full explanation

Answer: A. maximum dry density

OMC/OWC is the water content at the peak of the compaction curve, i.e. where dry density is maximum for the given effort.

Question 8Medium

In a compaction test, the dry unit weight stops increasing after optimum moisture content because:

Full explanation

Answer: D. water particles start occupying space of soil grains

Beyond OMC, the extra water fills voids that soil grains could have occupied; since water is nearly incompressible, the solids are pushed apart and dry density drops.

Question 9Medium

Study the following statements with respect to compaction of soils and identify the correct option. Statement A: Fine-grained soils attain a much higher density and lower optimum water content when compared to well graded coarse-grained soils. Statement B: Compacted density of soil increases as water content increased, till a maximum dry density is achieved.

Full explanation

Answer: A. Statement B is correct and A is incorrect

A is reversed: well-graded coarse soils give higher MDD and lower OMC. B correctly describes the dry side of the compaction curve.

Question 10Hard

A laboratory compaction test conducted on a soil sample having specific gravity equal to 2.65 gave a maximum dry density of 1.8 g/cm³ and a degree of saturation of 96%. Take density of water ρw = 1 g/cc. Find the optimum moisture content and air content.

Full explanation

Answer: A. 17.10%; 4%

e = 2.65/1.8 − 1 = 0.472; w = Se/G = 0.96×0.472/2.65 = 17.1%; air content ac = 1 − S = 4%.

Question 11Easy

The moisture content at which a specified amount of compaction produces maximum dry density is known as ______.

Full explanation

Answer: A. optimum moisture content

That water content is the optimum moisture content (OMC).