Unveiling the Importance of The Standard Penetration Test

Acceptable foundation performance of construction projects relies on the quality and proper interpretation of the data collected during the geotechnical investigation.  While no amount of data would completely eliminate geotechnical risks, ignoring the adequate characterization of the ground supporting a structure can have disastrous consequences, costing time and money.  Our latest video highlights the method of Standard Penetration Testing as an important part of geotechnical investigations, particularly in North America, where it is most popular.

The widely used test involves hammering a sampling tool into the ground using a standardized driving sequence.  It is a simple and cost-effective site characterization method useful for obtaining soil samples at depth and for estimating shear strength, bearing capacity and compressibility of soils.

The test involves using a “split-spoon” sampler at the end of a metal rod driven into the ground in six-inch increments.  The number of hammer blows needed to advance the sampler two successive six-inch increments is defined as the SPT N-value, or SPT blow count, for the soil at the depth of the sampler.  Decades of field investigations involving collection of SPT data resulted in a wealth of geotechnical data and numerous correlations of the SPT N-value with other laboratory soil test results to estimate shear strength and other design parameters for assessing settlement, bearing capacity, liquefaction potential and many other geotechnical concerns.

The analysis of the data provided by the Standard Penetration Test gives a more complete picture of the soil characteristics for the purpose of designing safe and enduring structures.