Which statement about the standard penetration test (SPT) is NOT true?

Which statement about the standard penetration test (SPT) is NOT true?

• A. The SPT is performed by driving a standard sampler 9 inches into the soil using a 100 lb hammer
• B. The SPT measures the number of blows required to drive the sampler to a standard depth
• C. The SPT results are used to estimate soil properties
• D. The SPT is a standard method used in geotechnical investigations

Answer: (A)

The test uses a split-spoon sampler driven into soil with a fixed energy, and the number of blows needed to advance the sampler a standard depth is recorded. This N-value is then related to soil properties and used in geotechnical investigations. The statement claiming 9 inches of penetration with a 100 lb hammer isn't accurate. In standard practice, the sampler is driven by a 140 lb hammer dropped from 30 inches, after seating the sampler with an initial penetration (commonly 6 inches), and the blows counted are those needed to drive the sampler a further 12 inches. That 12-inch drive, not 9 inches, and the 140 lb hammer, not 100 lb, are the accepted norms. The other statements are correct: the test measures blows to reach a standard depth, its results are used to estimate soil properties, and it is a standard method in geotechnical investigations.

The test uses a split-spoon sampler driven into soil with a fixed energy, and the number of blows needed to advance the sampler a standard depth is recorded. This N-value is then related to soil properties and used in geotechnical investigations.

The statement claiming 9 inches of penetration with a 100 lb hammer isn't accurate. In standard practice, the sampler is driven by a 140 lb hammer dropped from 30 inches, after seating the sampler with an initial penetration (commonly 6 inches), and the blows counted are those needed to drive the sampler a further 12 inches. That 12-inch drive, not 9 inches, and the 140 lb hammer, not 100 lb, are the accepted norms. The other statements are correct: the test measures blows to reach a standard depth, its results are used to estimate soil properties, and it is a standard method in geotechnical investigations.