4. Standard Penetration Test (SPT)

Objectives - The standard penetration test (SPT) is an in-situ dynamic penetration test designed to provide information on the geotechnical engineering properties of soil. The test provides samples for identification purposes and provides a measure of penetration resistance which can be used for geotechnical design purposes. Many local and widely published international correlations which relate blow count, or N-value, to the engineering properties of soils are available for geotechnical engineering purposes. The test is extremely useful for determining the relative density and the angle of shearing resistance of cohesionless soils. A split barrel sampler is driven into the soil by 63.5kg weight falling through 75 cm height. After an initial set of 15 cm, the no. of blows required to drive the sampler an additional 30cm is known as Penetration resistance or “N” value. The “N” values are indicative of the relative density of cohesion less soils and consistencies of cohesive soils. Each sample retrieved from SPT spoon was inspected for visual identification of strata as per IS 1498. The samples were preserved in polythene bags duly numbered for proper identification.