Question

Soil Mechanics (300985) - Practice for final exam SESSION 2 SCC 2018 Question 1 a C The results of a dry-sieving test are given in Table 1. Plot the particle size distribution curve and give classification for the soil in accordance with USCS. (The standard graph paper and classification figure are paper). available at end of this exam Table 1. Sieve analysis sample Sieve analysis of a soil sample Mass Percent finer Sieve Mass by weight passing M(g) Sieve No. opening (mm) retained M (g) 0.00 4.750 2000 4 23 10 0.850 5.16 20 15 48 35 0 500 60 0 250 42 29 100 0.150 113.59 200 0.075 9.65 0.15 pan 190 55 The following may be useful in the calculation: D D: DgD

Answer 1

Sieve No.	Sieve openning (mm)	Mass retained (g)	Percentage mass retained = (Mass retained / Total mass)* 100	Cumulative percentage retained	Percentage finer
4	4.75	0	0.000	0	100.000
10	2	4.23	2.220	2.220	97.780
20	0.85	5.16	2.708	4.928	95.072
35	0.5	15.48	8.124	13.052	86.948
60	0.25	42.29	22.194	35.245	64.755
100	0.15	113.59	59.612	94.857	5.143
200	0.075	9.65	5.064	99.921	0.079
Pan		0.15	0.079	100.000	0.000
		Total mass = 190.55

Particle size distribution curve 120.000 100.000 80.000 60.000 40.000 20.000 0.000 0.01 0.1 10 1 Sieve opening (mm) Percentage finer (%

From the above graph we get,

D₁₀ = 0.155 mm (Refer X-axis value corresponding to the brown line)

D₃₀ = 0.18 mm   (Refer X-axis value corresponding to the yellow line)

D₆₀ = 0.24 mm   (Refer X-axis value corresponding to the green line)

Therefore,

Coefficient of uniformity (C_u) = D60 / D10

= 0.24/0.155

= 1.548

Coefficient of curvature (C_c) = D₃₀² / (D₁₀ * D₆₀)

= 0.18² / (0.155 * 0.24)

= 0.871

Classification of the above soil by USCS method:

Cumulative percentage retained on No.200 sieve = 99.92 % > 50 %

Therefore, the given soil is Coarse grained soil.

Cumulative percentage retained on No. 4 sieve = 0 % < 50 %

Therefore, the given soil is Sand.

Now,

For well graded sand: C_u$\geqslant$ 4 and C_c = 1 to 3

In comparison our obtained values are: Cu = 1.548 < 4 and Cc = 0.871 (is not between 1 and 3)

Therefore the given soil can not be well graded sand.

Hence the given soil is Poorly graded sand (SP)