Concept:

a) The maximum dry density obtained increases with increase in compaction effort. The higher compaction energy applied, closer will be packing of materials leading to high dry density and low Optimum moisture content.

b) Since IS heavy compaction test (modified proctor test) imparts more compaction energy n IS light compaction test (standard proctor test), so option a) is correct.

c) Fine soils have relatively more OMC but less maximum dry density compared to coarser soil because due to high specific surface is more water is required for lubrication, hence showing a higher OMC.

d) Fine-grained soils have a higher void ratio, occupying more volume and hence shows a lesser value of maximum dry density compared to coarser soil. Hence option b) is incorrect and d) is correct.

e) Zero air voids line is line that indicates an imaginary situation where re is no air in soil and hence air content in soil is 0and  unit weight corresponding to this condition is called zero air void unit weight and  Sr (Degree of saturation) + Ac (Air content) = 1, So degree of saturation will be 1 for zero air content.

Therefore, option c) is also correct.

Explanation:

(i)The Indian Standard Equivalent of Standard Proctor Test is called light compaction test (IS: 2720 Part VII - 1974).

(ii) The Indian Standard Equivalent of Modified Proctor Test is called heavy compaction test (IS: 2720 Part VIII - 1983).

In compaction test:

Concept:

Compaction Equipment:

• It is often got by using a vibrating or non-vibrating steel drum roller, a pneumatic-tire roller, a grid or cleated roller, or a sheep-foot roller.

Pneumatic tyred rollers:

• Suitable for soil type: Non-plastic silts and fine sands, not suitable for uniformly graded soil
• Nature of Project: Base, sub-base, and embankment compaction for highways, airfields, etc.

Different compaction equipment with suitable soil is as follows:

In Jodhpur mini compaction test, mould has effective height of 60 mm and internal diameter of 79.8 mm. Therefore volume of cylinder is,
?r² h=?*79.8²*60 mm³=0.3 litres.

In Standard Proctor test, test equipment is a cylindrical metal mould that has an internal diameter of 4 inches or 10.15 cm.

The attainment of maximum density at full saturation is due to reduction of effective pressure between soil particles by hydrostatic pressure.

The initial water content may be taken as 4 % for coarse-grained soils and 10 % for fine-grained soils as quantity of water to be added for first test depends on probable optimum water content for soil.

In Jodhpur mini compaction test, soil is compacted in 2 equal layers. In Modified Proctor test number of layers of soil is compacted is five. While in Standard Proctor test number of layers of soil is compacted is three.

In Standard Proctor test, test equipment is a cylindrical metal mould that has an internal effective height of 4.6 inches or 11.7 cm.

The vibrators consist of vibrating unit of eir out-balance weight type or a pulsating hydraulic type mounted on a screed, plate or roller.