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Standard Penetration Test (SPT) energy calibration

SPT is an in situ dynamic penetration test designed to provide information on geotechnical engineering properties of soil. The number of blows required to penetrate the last 12" is the “N value”, which is related to soil strength. The quality of the test result depends on various factors, such as actual energy delivered to the head of drill rod, dynamic properties of drill rod, the method of drilling and borehole stabilization. The actual energy is one of the factor which affects the reliability of SPT. Therefore as per codes, it is utmost important to check the performance of hammer periodically.

The Pile Driving Analyzer® (PDA) measures the energy transferred by the SPT hammer to the SPT rod which is instrumented with strain transducers and accelerometers gauges.

We perform this service in accordance with following standards:

ASTM D4633-10 : Standard Test Method for Energy Measurement for Dynamic Penetrometers

ASTM D1586-08 : Standard Test Method for Penetration Test and Split-Barrel Sampling of Soils,

ASTM D6066-96(2004) : Standard Practice for Determining the Normalized Penetration Resistance of Sands for Evaluation of Liquefaction Potential.

Becker hammer energy measurement

The Backer Penetration Test (BPT or Backer Drill Tests) is used in geotechnical investigation for coarse grained soils that are too hard to be tested with SPT. The test is particularly useful when liquefaction is concern in earthquake-prone areas. A diesel impact hammer drives a hefty double walled pipe into the ground. As in the SPT test, the number of blows required to drive the last 300 mm in record. This number is corrected to SPT blow counts to assess soil strength.

The energy output of the Becker Drill diesel hammer varies depending on the air-fuel mixture, temperature, pressure, soil resistance and hammer performance. In order to account for this variability, the hammer energy must be measured. The most reliable way to determine the energy is by force and acceleration measurement and processing by the Pile Driver Analyser®. For an accurate assessment to know how much of the resistance occurs at the pile toe. Only by knowing the end bearing component can the BPT blow count be reliably used.

Our engineers use Pile Driving Analyser to measure the energy transferred into Becker casing instrumented with strain transducers and accelerometers. Further analysis for the resistance distribution can be obtain by performing CAPWAP analysis.

This test is complaint with ASTM D4633-10 Standard Test Method for Energy Measurement for Dynamic Penetrometers.

ASTM D6066-96(2004) Standard Practice for Determining the Normalized Penetration Resistance of Sands for Evaluation of Liquefaction Potential.

 
 
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