Standard Penetration test
Standard: ASTM D 1586 AASHTO T 20
• The Standard Penetration Test, or SPT, is the most widely used in-situ test throughout the world, as an indicator of the density and compressibility of granular soils. It is also commonly used to check the consistency of stiff or stony cohesive soils and weak rocks. Estimation of the liquefaction potential of saturated granular soils for earthquake design is often based on these tests. Available design methods for both shallow and deep foundations rely heavily on SPT results.
• The test consists of driving a standard 50-mm outside diameter thickwalled sampler into soil at the bottom of a borehole, using repeated blows of a 63.5 kg hammer falling through 760 mm. The SPT N value is the number of blows required to achieve a penetration of 300 mm, after an initial seating drive of 150 mm.