The Standard grain size analysis test determines the relative proportions of different grain sizes as they are distributed among certain size ranges.
Need and Scope:
The grain size analysis is widely used in classification of soils. The data obtained from grain size distribution curves is used in the design of filters for earth dams and to determine suitability of soil for road construction, air field etc. Information obtained from grain size analysis can be used to predict soil water movement although permeability tests are more generally used.
Notice: The balance to be used should be sensitive to the extent of 0.1% of total weight of sample taken.
|sieve #||Sieve size (mm)||Mass of each sieve (mm)||Mass of each sieve + retained soil||Mass of soil
Percentage on each sieve Rn
|Cumulative percent retained S Rn||% finer, 100- S Rn|
|Pan||S = W1=|
Column 5 = Column4 - Column3
Column 6 = Column5 / (Total mass in step 3)
Calculate the cumulative percent of soil retained on the nth sieve,
= S Rn
Calculate the cumulative percent passing through the nth sieve,
= Percent finer = 100 - S Rn or 100 - Column 7
Interpretation and Reporting the Results:
Draw graph of log sieve size vs % finer. The graph is known as grading curve. Corresponding to 10%, 30% and 60% finer, obtain diameters from graph these are D10, D30, D60, using these obtain Cc and Cu which further represent how well the soil is graded i.e whether the soil is well-graded, gap-graded or poorly graded.
A sample Calculation is given here;