Aggregate Size Analysis by Wet Sieving Method

MWD is equal to the sum of the products of (I) the mean diameter (di) of each size fraction and (ii) the proportion of the total soil sample weight (wl) occurring in the corresponding size fraction, where the summation is carried out over all n size fractions including the one which passes through the finest sieve. [The entire soil sample must be passed through a 8 mm sieve prior to analysis]. 

Y = percent of soil particles 0.25 mm in diameter obtained by wet sieve aggregate analysis method. 

Stability index (S.I) is usually evaluated by measuring the area between the curves of aggregate distribution and primary particles distribution on the coarser side of intersection (Fig. 2.3a). 

Area of coarse side of intersection (measured by planimeter) 

Aggregate Index (A.I.) is obtained by measuring the area between the two curves obtained by plotting the percentage of soil particles below a size range against that size class 

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