A soil has a dry density of 17.5kN/m³. It has densities corresponding to most compact and loosest state as 18.5 kN/m³ and 13 kN/m³ respectively. The relative density of the soil is ______
a) 0.871
b) 0.865
c) 0.869
d) 0.860

Answer: b
Explanation: Given,
Dry density γ_d=17.5 kN/m³
Maximum dry density γ_d,max=18.5kN/m³
Minimum dry density γ_d,mim=13kN/m³
Relative density I_D= \(\frac{(γ_d-γ_{d,min})γ_{d,max}}{((γ_{d,max}-γ_{d,min}) γ_d )}\)
I_D = \(\frac{((17.5-13)*18.5)}{((18.5-13)*17.5)}\)
I_D=0.865.