Compaction

compaction test

General

Granular soil is compacted with a standard amount of energy over a range of moisture contents to identify the optimum moisture content for maximum compaction.

Fills for highways and buildings must be compacted to attain appropriate strength and minimize settlement. The most common method of specifying compaction is to require a certain percent of the maximum that can be attained in proctor compaction tests.

The original moisture-density test was developed by R.R. Proctor and is commonly referred to as the Standard Proctor Test, Proctor Test, or Standard Moisture-Density Test. The Modified Proctor or Modified Moisture-Density Test is performed the same way but in a larger mold with higher compactive energy. Each of the approximately 8 different variations of standard and modified proctor se can produce different results, so contract documents must specify which procedure is to be used.

Apparatus

Standard Proctor (5.5 lb, 12-in. drop) Hammer; Standard Procotor (1/30 ft³=944cm³) Mold; Moisture cups; Straight Edge; Spatula; Sprinkler Bottle; Paint Brush; Large Mixing Pan; #4 sieve Scale accurate to 0.01g for water content samples; Scale accurate to 0.01 lb. or 1 g for weighing mold

Procedure

Procedure

Take 2kg of sample and add 2% of water by weight and mix thoroughly.
Record the empty weight of mold.
Place the extension collar on the mold and put the sample to approximately half of the mold height. This is to ensure that the sample will reach one third of the height of the mold after compaction.
Compact the sample in three layers at the rate of 25 blows per layer
Remove the extension collar and trim the sample even with the top of the mold using the straight edge.
Record the weight of mold with sample.
Remove the entire sample and place it in a can whose weight has been recorded. Take the weight of can with sample. Then, place it in a n oven to determine the moisture content.
Repeat the above steps with increasing water contents of 4,6,8,10 and 12 percentages.
Calculate the dry unit weight and plot it with water content. Find the optimum water content from the plotted graph.

NOTE:

	Final compacted sample height should not be less than the mold height.
	Make sure to remove the collar before taking weight.
	A minimum of 4 tests on dry side of optimum and two on wet side of optimum should be performed.

Data Sheets [right-click | "save target as" Excel 2000]

References

Report Format

Results

Al-Khafaji & Andersland (1992), pages 530-539.

Lambe (1951), 43-51.

Your report should include the following:

1.A description of the soil.

2.A sample of the calculations used to determine dry density and moisture content.

3.A plot showing the variations of dry density with moisture content for both hammer weights (draw both sets of data on the same graph).

4.On the same plot draw the zero-air voids line for this soil.

5.The optimum moisture contents and maximum dry densities.

6.A comment on the effects of increasing compactive effort observed in the experiment.

7.Discussion of the benefits of increasing compactive effort in engineering practice. Are there any disadvantages?

8.Calculate the degree of saturation of the soil at the optimum moisture content.