Soil Testing Required for Road Construction
Generally, when it come to construction on soils, tests should be performed to understand the nature of soil that the building is going to be constructed on.
In this article, the basic tests required for the construction of roads and highways are briefly mentioned.
Common test are: Soil classification, particle size distribution, moisture content determination, specific gravity, liquid limit and plastic limit tests. Moisture content, particle size and specific gravity tests.
In almost all soil tests natural moisture content of the soil is to be determined. The knowledge of the natural moisture content is essential in all studies of soil mechanics. To sight a few, natural moisture content is used in determining the bearing capacity and settlement. The natural moisture content will give an idea of the state of soil in the field.
Specific gravity of soil
The knowledge of specific gravity is needed in calculation of soil properties like void ratio, degree of saturation etc. It is the ratio of the weight of soil in air of a given volume at a standard temperature to the weight in air of an equal volume of distilled water at the same stated temperature.
Particle Size Distribution
Particle size distribution, also known as gradation, refers to the proportions by dry mass of a soil distributed over specified particle-size ranges. Gradation is used to classify soils for engineering and agricultural purposes, since particle size influences how fast or slow water or other fluid moves through a soil.
This soil compaction test also called as Proctor test is used for the determination of the mass of dry soil per cubic metre when the soil is compacted over a range of moisture contents, giving the maximum dry density at optimum moisture content. Thus this test provides the compaction characteristics of different soils with change in moisture content. This is achieved by densification of soil by reducing the air voids.
The degree of is measured in terms of its dry density of soil. The dry density is maximum at the optimum water content.
California Bearing Ratio Test
California Bearing Ratio test is conducted in laboratory. This tests provides the load penetration resistance of soil. CBR value is obtained by measuring the relationship between force and penetration when a cylindrical plunger is made to penetrate the soil at a standard rate.
The CBR test is used for the evaluation of subgrade strength of roads and pavements. The CBR value obtained by this test is used with the empirical curves to determine the thickness of pavement and its component layers. This is the most widely used method for the design of flexible pavement.