Correct option is D
Smear Zone: It is a zone in sand or a free fabricated vertical drain is created by the remolding of clay during the operation of building it.
Due to the formation of smear zones, the effectiveness of soil drains is reduced.
The compressibility of surrounding soils is increased and which in turn leads to the reduction of their permeability.
Due to this reduction in permeability of soils, it takes a longer time to complete the consolidation process.
The radial distance from the center line of the drain well to the farthest point on the smear zone is equal to the radius of the smear zone.
