How to Test Soil Compaction

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.

2) California Bearing Ratio
The California bearing ratio (CBR) is used as a determine the quality of strength of a soil under a pavement. It also measures the thickness of the pavement, its base, and other layers.
CBR = F/F_o
where
F = force per unit area required to penetrate a soil mass with a 3-in² (1935.6-mm² ) circular piston (about 2 in (50.8 mm) in diameter) at the rate of 0.05 in/min (1.27 mm/min)

F₀ = force per unit area required for corresponding penetration of a standard material.

3) Soil Permeability
Darcy’s law is applicable in determining the soil permeability. Darcy law states that
V = kiA

where
V = rate of flow, cm³ /s,
A = cross-sectional area of soil conveying flow, cm²
k = Coefficient of permeability which depends on grain-size distribution, void ratio and soil fabric. The value varies from 10 cm/s for gravel to less than 10^–7 for clays.