63
3
rd
quartile (d 25) : Size of sieve which separates 75 percent of coarser
material.
Screen size : Size of sieve which separates 40 percent of coarser materials.
Effective size (d10) = Size of sieve which separates 90 percent of coarser
materials.
Sorting co-efficient = d75 / d25
Uniformity Co-efficient = d 60 / d10
The above statistical information are helpful in respect of aquifer materials to be
tapped during construction of well.
Fig. 6.3. Cumulative Curve of grain size distribution
(After Karanth, 2004)
