(a) Particle size distribution curves for 3 soil samples collected from the fiel
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Question
(a) Particle size distribution curves for 3 soil samples collected from the field are shown in Figure 4.1 below. Based on the figure, (i) Give the best laboratory techniques to obtain particle size distribution curves for these3 types of soils. (1.5 marks) (ii) Name the 3 soils according to the USCS (Unified Soil Classification System) standard. (1.5 marks) (iii) Is soil A uniform or distributed? Justify your answer with a uniformity coefficient (1 mark) calculation. 200 14010070504030 20 12 5 4 * *l" 1 200150 1007252352534107*.1·1. 100 90 80 70 60 50 40 30 20 10 _Soil A Soil B Soil C 2 0010002006 0.01 0.0t 0.1 2 05 10 Equivalent Particle Size (mm) MedumCoarse MediumCoarse Clay ravel CoarseStone or Figure 4.1 (b) A soil sample collected in a summer season is fully dry and has 260 g of total mass, 200 cm of total volume and specific gravity of 2.6; (i) What is the sample void ratio? Base your answer on a phase diagram analysis. 4 marks) (ii) What is the sample dry density? Base your answer on a phase diagram analysis (2 marks)Explanation / Answer
(a)
(i) The best laboratory techniques to obtain this kind of particle size distribution of soil is the Sieve Method
The percentage of particular grain size is calculated by:
Pa= (Ma/Mt)*100
where, Ma and Mt are the masses of grain A and total soil respectively
(ii) According to the USCS, Soil A is ML
Soil B is SP
Soil c is GW
(iii) Coefficient of uniformity = D60/D10 = 0.0017/ 0.0015 = 1.133 which implies the Soil A is uniformly distributed.
(b)
Void Ratio= Volume of void/ Volume of Solid
to find the voulme of solid= Mass of soild/ (Specific gravity*density)
= (.260)/(2.6*1000)
=.0001 m3=Vs
Volume of void= Total volume- Volume of soil
= (0.0002-0.0001)= 0.0001 m3= Vv
Void ratio= Vv/Vs = 1
(ii) Sample dry density= Mass of soil/ Volume
.260kg/.0002 = 1300 kg/m3
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