To determine the uniformity coeffient of sand (from a chosen source):
First: Take a small sample of the sand and determine the sand grain size (wire mesh hole size opening) at which 60% of this small sample‘s weight passes through the holes in a sifting appratus such as wire mesh, and 40% of it does not pass through the holes in that same sifting apparatus.
Second: Then take another small sample of the same sand. Make sure it is the same weight as the first small sample. Then determine the sand grain size (wire mesh hole size opening) at which 10% of this small sample‘s weight passes through the holes in a another sifting appratus such as wire mesh, and 90% of it does not pass through the holes in the same sifting appratus used in this second sifting operation.
Use the same mesh pattern for the first and second operation. However, the mesh opening sizes in the first operation will be different than the mesh opening sizes in the second operation.
Then know that for an equal weight of sand the uniformity coefficient equals:
the sand grain size at which 60% goes through and 40 % is retained
divided by
the sand grain size at which 10% goes through and 90% is retained