500 g of dry soil was used for a sieve analysis. The masses of soil retained on each sieve are given below:

Question

US standard sieve	Mass in g	US standard sieve	Mass in g
2.00 mm	10	500 μ	135
1 .40 mm	18	250 μ	145
1.00mm	60	125 μ	56
		75 μ	45

Plot a grain size distribution curve and compute the following:

(a) Percentages of gravel, coarse sand, medium sand, fine sand and silt, as per the Unified Soil Classification System, (b) uniformity coefficient (c) coefficient of curvature.

Comment on the type of soil.

Accepted Answer

Computation of percent finer
US standard sieve	Diameter, D of grains in mm	Mass retained in g	% retained	Cumulative % retained	% finer P
2.00 mm	2	10	2	2	98
1 .40 mm	1.4	18	3.6	5.6	94.4
1.00mm	1	60	12	17.6	82.4
500 μ	0.5	135	27	44.6	55.4
250 μ	0.25	145	29	73.6	26.4
125 μ	0.125	56	11.2	84.8	15.2
75 μ	0.075	45	9	93.8	6.2

(a) Percentage coarse to medium sand = 98 - 48 = 50 percent

Percentage fine sand = 48 - 6.2 = 41.8 percent

Percentage silt and clay = 6.2 percent.

(b) Uniformity coefficient [latex]C_{u}=\frac{D_{60}}{D_{10}}=\frac{0.58}{0.098}=5.92[/latex]

(c) Coefficient of curvature [latex]C_{c}=\frac{\left(D_{30} ight)^{2}}{D_{10} imes D_{60}}=\frac{(0.28)^{2}}{0.098 imes 0.58}=1.38[/latex]

The soil is just on the border line of well graded sand.

Question 3.12: 500 g of dry soil was used for a sieve analysis. The masses ...

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