SSC JE Civil Engineering 23-Mar-2021 Shift 1 Paper

Concept:
Dry Unit Weight (γd):
It is a measure of the weight of solid particles per unit volume.
γd=Ws∕V
Where Ws= weight of solid particles, V= Volume of solid particles
Now the relationship between the specific gravity of solid particles, void ratio, and dry unit weight
γd=

Gγw

(1+e)

where G = specific gravity of solid particles, e = void ratio
Calculation:
GivenData:
The mass of a chunk of moist soil = 20 kg
The dry density of soil (γd)=1500‌kg∕m3
Specific gravity (G)=2.50
The density of water (γw)=1000‌kg∕m3
Using the relationship between the specific gravity of solid particles, void ratio, and dry unit weight
γd=

Gγw

(1+e)

1500=

2.50×1000

(1+e)

(1+e)=

2.50×1000

1500

e = 0.6667
The void ratio is 66.67%