Section 4: Soil and Water Conservation Engineering
Soil Mechanics
Subtopic: Index properties of soils
Question Statement:
A soil has bulk density and particle density of 1.48 Mg m⁻³ and 2.64 Mg m⁻³, respectively. The saturated volumetric moisture content of soil is 36%. The porosity and void ratio of the soil are
Options:
(A) 0.36 and 0.56
(B) 0.44 and 0.79
(C) 0.79 and 0.44
(D) 0.56 and 0.36
Official Answer Key:
B
Step-by-Step Solution & Explanation
Porosity n = 1 − (bulk density/particle density) = 1 − (1.48/2.64) = 1 − 0.5606 = 0.4394 ≈ 0.44. Void ratio e = n/(1−n) = 0.4394/0.5606 = 0.7838 ≈ 0.79. This gives 0.44 and 0.79 → option (B) (the saturated volumetric moisture content, 36%, is a distractor value not needed for this particular calculation since bulk and particle densities alone define porosity/void ratio). Option (C) swaps n and e; (A)/(D) mix up the given 36% figure with the computed porosity.
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