If a soil uniformity coefficient is less than 3, coefficient of curvature greater than 3 and having more than half of coarse fraction (+75 micron i.e. retained on 75 microns IS sieve) Is smaller than 4.75 mm IS sieve, then the classification of the soil is.

Question

Question

This question was previously asked in

HPPSC AE Civil 2016 (HPPTCL) Official Paper

Answer 1

Concept:

Soil classification:

% of fraction passing through 75 μ sieve	Gravel (G) ( > 4.75 mm)		Sand (S) ( 425 𝛍 to 4.75 mm)		Remarks
	Well Graded (W) If C_u > 4 C_c = 1 to 3	Poorly Graded (P) (Else)	Well Graded (W) If C_u > 6 C_c = 1 to 3	Poorly Graded (P) (else)
1. p < 5 %	GW	GP	SW	SP	Gradation only governs the properties
2. p (5 to 12 %)	GW – GC or GW – GM	GP – GC or GP – GM	SW – SC or SW – SM	GP – GC or GP - GH	Dual symbol check the presence of either clay (C) or silt (M), using plasticity chart
3. p > 12%	I_P < 7 %	I_P > 7 %	I_P < 4 %	I_P > 4 %	The presence of fine particles dominate the soil characteristics
3. p > 12%	GM	GC	SM	SC

Here,

C_u - Coefficient of uniformity

C_c - Coefficient of curvature

Explanation:

Given,

More than half of the coarse fraction < 4.75 mm IS sieve → Sand

C_u < 3 → Poorly graded

Hence,

The given soil is classified as Poorly graded sand.