NPK C2D - Page 25

NPK
- 20 -
SOIL DENSITY TESTING
Standard Proctor Test. A Standard Proctor soil test is conducted as follows:
A soil sample is taken from the job location and placed in a container equal to 1/30
cubic foot. A 5-1/2 pound weight with a striking face of 3.1 square inches is dropped 12
inches for 25 blows on each of the three equal layers. The soil material is then
weighed, less the mold, and recorded as wet weight/cubic ft. The material is then oven
dried for 12 hours in order to evaluate the water content.
Modified Proctor Test. The Modified Proctor test is done in much the same way as
the Standard Proctor test, except a 10 pound hammer is used and dropped from a
distance of 18 inches for 25 blows. The material is placed in five equal layers in a
container 1/30 cu. ft. The compaction effort produced is 56,200 foot pounds while the
Standard Proctor test produces 12,400 foot pounds. The Modified test is normally used
in testing materials for higher shearing strength, which would likely be used in
supporting heavier loads.
Fig. 3
STANDARD PROCTOR TEST
Fig. 4
MODIFIED PROCTOR TEST
cp12
Soil Sample 1/30 cu. ft. – 3 layers
cp13
Soil Sample 1/30 cu. ft. – 5 layers
cp14
Compaction Energy 12,400 ft. lbs. (16,740 Nm)
cp15
Compaction Energy 56,200 ft. lbs. (75,870 Nm)
cp16
25 Blows per Layer