Question

If the permeability, shrinkage and swelling of a compacted soil having same density on dry side of optimum moisture content is compared with compaction on wet side of optimum, the variation in these properties will be
1. more, less, higher
2. more, more, higher
3. more, more, less
4. less, less, higher

Answer 1

Correct Answer - Option 1 : more, less, higher

Explanation:

• For the same density, fine-grained samples compacted dry of optimum are more permeable than those compacted wet of optimum. This is so because soils have flocculated structure when compacted dry of optimum, and have dispersed structure (parallel orientation) when compacted wet of optimum. And flocculated structure has less permeability.
• For the same density, the soil sample compacted dry of optimum shrink appreciably less than the sample compacted wet of optimum. This is so because the soil particles having dispersed structure have nearly parallel orientation and can pack more efficiently.
• A clayey soil sample compacted dry of the optimum water content has high water deficiency and more random orientation and hence exert greater swelling pressure and swell higher to water content than the sample of the same density obtained from the wet side compaction.

•  The saturated sample of clay compacted wet side of optimum is more compressible than another sample of the same soil, having the same void ratio, but compacted dry of the optimum, when the applied pressure is in low range.
• this is so because the sample compacted dry of optimum has flocculated structure and requires extra pressure to cause the parallel orientation of particles.