Question

a)

A Standard Penetration Test (SPT) is conducted to measure the in situ strength of A-7-6 subgrade soil. The number of blows required to drive the split spoon sampler into the ground were as follows

b)

The maximum dry density for a soil obtained in the lab at 11% moisture content is 122.4 pcf If the measured field bulk density was 131.6 pcf at 10% water content, what is the percent compaction achieved for this soil in the field?

C)

If an HMA sample core density is 133.5 pcf, and the maximum theoretical density determined at the lab was 143.1 pcf, the percent air voids for this sample is most nearly

Answer 1

a) A Standard Penetration Test (SPT) is conducted to measure the in situ strength of A-7-6 subgrade soil. The number of blows required to drive the split spoon sampler into the ground is the sum of the number of blows required to drive the sampler for one foot into the ground (second 6 in blows + third 6 in blows).

b) The maximum dry density for a soil obtained in the lab at 11% moisture content is 122.4 pcf.

The measured field bulk density was 131.6 pcf at 10% water content.

Field dry density = Bulk density/(1+(0.01 * water content)) = 131.6/(1+0.01*10) = 131.6/1.1 = 119.636 pcf

% Compaction = Field dry density/Lab dry density * 100 = 119.636/122.4 *100 = 97.74%

C) HMA sample core density = 133.5 pcf

Theoretical density = 143.1 pcf

Percent air voids = (Theoretical density - core density)/Theoretical density * 100

= (143.1 - 133.5)/143.1 * 100 = 6.71 %