Question

A soil sample has a dry density of 8.5 kN/m^3, specific gravity of solids G as 2.7 and voids ratio of 0.6. If the unit weight of soil is 50% saturated, then its bulk unit weight will be ______

(a) 19.274 kN/m^3

(b) 23.034 kN/m^3

(c) 20.554 kN/m^3

(d) 21.428 kN/m^3

I got this question by my college director while I was bunking the class.

The query is from Functional Relationships topic in division Preliminary Definitions and Relationships of Geotechnical Engineering I

Answer 1

Right option is (c) 20.554 kN/m^3

The explanation is: Given,

Dry density γd = 18.5 kN/m^3

Specific gravity G=2.7

Void ratio e= 0.6

Degree of saturation = 50% = 0.5

Since, e = (W*G)/S

W = (e*S)/G=(0.6*0.5)/2.7=0.111

Bulk unit weight γ=γd(1+W)

γ=18.5*1.111=20.554 kN/m^3.