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Road base void ratio specification

Short answer

Dry unit weight is 15.65 kN/m³ giving void ratio 0.692, which is below the specified 0.75, so the bill should be passed.

You are appointed as a supervisor for a road construction project. During the construction process, the contractor compacted the base course of the road and the average water content for the test samples was found to be 15%, the specific gravity of soil grains = 2.7 and unit weight of soil = 18 kN/m³. The specification requires that void ratio < 0.75. If you have to pass the bill for that task according to the specification, would you pass the bill for that work?

Given

w=15%w = 15\%, G=2.7G = 2.7, γ=18\gamma = 18 kN/m³, specified e<0.75e < 0.75. Take γw=9.81\gamma_w = 9.81 kN/m³.

Solution

Dry unit weight:

γd=γ1+w=181.15=15.65 kN/m3\gamma_d = \frac{\gamma}{1+w} = \frac{18}{1.15} = 15.65\ \text{kN/m}^3

Void ratio from γd=Gγw1+e\gamma_d = \dfrac{G\gamma_w}{1+e}:

e=Gγwγd−1=2.7×9.8115.65−1=0.692e = \frac{G\gamma_w}{\gamma_d} - 1 = \frac{2.7 \times 9.81}{15.65} - 1 = 0.692

Since e=0.692<0.75e = 0.692 < 0.75, the compaction meets the specification.

Decision: pass the bill for this base course work. (A check using the average of several samples is taken as given; individual samples should also be checked.)

✓ Answer checked by Claude Opus 5.5 (high effort)

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