Zero air voids lines
A-line, which shows the relation between water content and dry density of compacted soil having a constant percentage of air voids is known as air void lines, which may be represented by as,
ɳa = Percentage of air voids
W = water content of compacted soil
ˠw = unit weight of water
The theoretical maximum compaction of soil for any given water content corresponding to zero-air voids condition i.e. ɳa = 0.
For a compacted soil the lines showing the relation between the water content and the dry density of the soil for a constant degree of saturation (s%) is known as saturation lines and which may be represented by as,