Standard Penetration Test: Its Uses and Abuses

In foundation test borings, the recovery of soil samples with a 2-in. OD split sample spoon driven with a 140-lb weight falling 30 in. has been in use for more than 30 yr. Recording the number of blows required to drive the spoon 12 in. has been called the Standard Penetration Test. It provides an approximation of soil densities in situ. It adds little to the cost of boring operations but adds considerably to the evaluation of the results when it is properly performed and it's are limitations recognized. This paper traces the history of the test, the modifications that have been introduced, the variables inherent in the test, and sets forth the factors that affect the results. Applications in granular and cohesive soils are examined.