Relative Density Test

5. RELATIVE DENSITY TESTS

5.1.1 OBJECTIVE

To determine the relative density of given coarse grained soil

5.1.2 Learning Outcomes

Understand the Principle of relative density

Maximum, minimum and natural densities and unit weights and methods of determining them (ASTM D 4253 & ASTM D 4254)

Perform the tests

Calculate relative density of the given soil sample

Write a report on the test exercise

5.1.4 Need and Scope

Relative density is an arbitrary character of sandy soil deposits. In real sense, relative density expresses the ratio of actual decrease in volume of voids in a sandy soil to the maximum possible decrease in the volume of voids i.e. how far the sand under investigation is capable to further densification beyond its natural state. Relative density and percent compaction are commonly used for evaluating the state of compactness of a given soil mass. Its determination is helpful in evaluating safe bearing capacity of sandy deposits. The engineering properties, such as shear strength, compressibility, and permeability, of a given soil depend on the level of compaction.

5.1.5 Principle

For a soil in its densest condition, its void ratio is the lowest and it exhibits the highest shear strength and the greatest resistance to compression. Porosity of a soil depends on the shape of graind, uniformity of grain sizes and condition of sedimentation. Hence porosity itself does not indicate whether a soil is in a loose or dense state. The compactness or denseness of granular soils can be evaluated quantitatively by the relative density (D_r). Relative density or density index is the ratio of the difference between the void ratios of a cohesionless soil in its loosest state and existing natural state to the difference between its void ratios in the loosest and densest states, Adeyeri (2015) and is defined