Standard Penetration Test (SPT)

ONE OF THE MOST POPULAR IN-SITU PENETROMETER METHODS

Standard Pentration Test (SPT) is a simple in-situ penetrometer test used for the estimation of geotechnical properties of the tested formation. Legion Drilling can assist you in the performance of SPTs by meeting all the international standards for equipment and methodology.

SPT consists of dropping a hammer of 63.5 kg over a split spoon sampler from a height of 0.76 m at a rate of 30 blows per minute. The number of blows required to advance the split spoon sampler 0.15 m into the formation is called the seating drive, while the number of blows needed to advance it other 0.30 m is called the standard penetration resistance or ‘N value’, which is used to characterise the formation. Additionally, a disturbed sample is collected during the test.

Since hammer systems may exhibit different energy transfer ratios (ETRs), N values are typically corrected to an energy level of 60% of total potential energy (N60). Legion Drilling provides fully automatic SPT hammers which represent the preferred option for consistent energy delivery.

CONE PENETRATION TESTING (CPT) AS A COST-EFFECTIVE ALTERNATIVE TO SPT

Legion Drilling recommends using reliable methods for geotechnical site investigations, including Cone Penetration Testing (CPT) or Piezocone Penetration Testing (CPTu). CPT and CPTu have been repeatedly found to be more accurate and less time consuming than SPT. Furthermore, CPT and CPTu estimate multiple geotechnical parameters (not just the N value) and are less expensive than SPT on a per data point basis. Additionally, direct push technology can be used to rapidly collect representative samples in adjacent locations.

FURTHER INFORMATION

Our technical specialists will be happy to provide further information and discuss in detail any specific project requirements.

In the meantime, we recommend you to consult the following documents: