Mechanical analysis on four different samples designated as A, B, C and D were carried out in a soil laboratory. The results of tests are given below. Hydrometer analysis was carried out on sample D. The soil is non-plastic. Sample D: liquid limit = 42, plastic limit = 24, plasticity index =18

Question

Mechanical analysis on four different samples designated as A, B, C and D were carried out in a soil laboratory. The results of tests are given below. Hydrometer analysis was carried out on sample D. The soil is non-plastic.

Sample D: liquid limit = 42, plastic limit = 24, plasticity index =18

Classify the soils per the Unified Soil Classification System.

Samples	A	B	C	D
ASTM Sieve Designation	Percentage	finer than
63.0 mm	100		93
20.0 mm	64		76
6.3	39	100	65
2.0 mm	24	98	59
600 μ	12	90	54
212 μ	5	9	47	100
63 μ	1	2	34	95
20 μ			23	69
6 μ			7	46
2 μ			4	31

Accepted Answer

Grain size distribution curves of samples A, B, C and D are given in Fig. Ex. 3.21. The values of [latex]C_{u}[/latex] and [latex]C_{c}[/latex] are obtained from the curves as given below.

Sample	[latex]D_{10}[/latex]	[latex]D_{30}[/latex]	[latex]D_{60}[/latex]	[latex]C_{u}[/latex]	[latex]C_{c}[/latex]
A	0.47	3.5	16.00	34.0	1.60
B	0.23	0.30	0.41	1.8	0.95
C	0.004	0.036	2.40	600.0	0.135

Sample A: Gravel size particles more than 50%, fine grained soil less than 5%. [latex]C_{u}[/latex], greater than 4, and [latex]C_{c}[/latex] lies between 1 and 3. Well graded sandy gravel classified as GW.

Sample B: 96% of particles are sand size. Finer fraction less than 5%. [latex]C_{u}=1.8, C_{c}[/latex] is not between 1 and 3. Poorly-graded sand, classified as SP.

Sample C: Coarse grained fraction greater than 66% and fine grained fraction less than 34%. The soil is non-plastic. [latex]C_{u}[/latex] is very high but [latex]C_{c}[/latex] is only 0.135. Gravel-sandsilt mixture, classified as CM.

Sample D: Finer fraction 95% with clay size particles 31%. The point plots just above the A-line in the CL zone on the plasticity chart. Silty-clay of low plasticity, classified as CL.

Question 3.21: Mechanical analysis on four different samples designated as ...

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