Correct Answer - Option 2 : Compaction increases the permeability of soil.
Concept:
The gradual decrease in volume of soil due to expulsion of air voids from it on application of load is called compaction of soil. This is significant in Granular soils like sand.
Effects of Compaction:
1. Due to compaction, soil particles comes closer to each other which in turn increases the mechanical interlocking in between them. Consequently increases angle of internal friction and hence, frictional resistance increases.
2. Due to increase in angle of internal friction of soil due to compaction its bearing capacity and shear strength also increases.
3. Due to reduction of air voids while compacting the soil, its permeability, porosity and void ratio reduces.
4. Compaction makes soil stiff; hence, tendency of settlement also got reduced.
