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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 procedure is described in the British Standard BS EN ISO 22476-3, ASTM D1586
NOTES on the STANDARD PENETRATION TEST
The Standard Penetration Tests aims to determine the SPT N value, which gives an indication of the soil stiffness and can be empirically related to many engineering properties.
The test is conducted inside a borehole. A 'split spoon' sampler is attached to the bottom of a core barrel and lowered into position at the bottom of the borehole. The sampler is driven into the ground by a drop hammer weighing 68 kg falling through a height of 76 cm. The number of hammer blows is counted. The number required to drive the sampler three successive 150mm increments is recorded. The first increment (0-150mm) is not included in the N value as it is assumed that the top of the test area has been disturbed by the drilling process. The SPT N is the number of blows required to achieve penetration from 150-450mm.
The hammer weight, drop height, spoon diameter, rope diameter etc. are standard dimensions.