Proctor-Compaction-Density by Sand Cone Method
DESCRIPTION AND PROCEDURE
The Proctor compaction test consists of compacting soil samples at a given water content in a standard mould with standard compaction energy. The standard Proctor test uses a 4-inch-diameter mould with the compaction of three separate layers of soil using 25 blows by a 5.5 lb hammer falling 12 inches.In the Proctor test, the soil is first air dried and and then separated into 4 to 6 samples. The water content of each sample is adjusted by adding water (3% – 5% increments or more depending on the type of the soil).
The soil is then placed and compacted in the Proctor compaction mould in three different layers where each layer receives 25 blows of the standard hamer. Before placing each new layer, the surface of the previous layers is scratched in order to ensure a uniform distribution of the compaction effects.
At the end of the test, after removing and drying of the sample, the dry density and the water content of the sample is determined for each Proctor compaction test. Based on the whole set of results, a curve is plotted for the dry unit weight (or density) as a function of the water content. From this curve, the optimum water content to reach the maximum dry density can be obtained.
SAND CONE-COMPACTION TEST
There are many types of Soil compaction tests which are performed on soil. Some of these are :-
1) The Sand Cone Method
One of the most common test to determine the field density of soil is the sand-cone method. But it has a major limitation that this test is not suitable for saturated and soft soils
The formula used are
Volume of soil, ft3 (m3)=[weight of sand filling hole, lb (kg)] /[ Density of sand, lb/ft3 (kg/m3)]
% Moisture = 100(weight of moist soil – weight of dry soil)/weight of dry soil
Field density, lb/ft3 (kg /m3)=weight of soil, lb (kg)/volume of soil, ft3 (m3)
Dry density=field density/(1 + % moisture/100)
% Compaction=100 (dry density)/max dry density
Maximum density is found by plotting a density-moisture curve.