SPT Analyzer Information
The SPT Analyzer is fully compliant with the minimum digital sampling frequency requirements of ASTM D4633-05 (50 kHz) and EN ISO 22476-3:2005 (100 kHz), as well as with the low pass filter, (cutoff frequency of 5000 Hz instead of 3000 Hz) requirements of ASTM D4633-05.
EMX is calculated as the maximum of the integral of force times velocity, over the whole record. It is the best theoretical method for calculating the maximum energy transferred to the foundation or SPT rod, and is the only one approved by ASTM 4633-05 and European Standard ISO 22476-3:2005 for SPT energy calculations. Because it searches the whole record, it is independent of the length (LE) setting. The EMX value is compared with the rated energy of the hammer to calculate ETR, that is, ETR (%) = 100 * EMX/PE, where PE is the maximum rated potential energy of the hammer.
EF2 was used exclusively for SPT energy measurements on previous versions of ASTM D4633, at a time when a reliable method for measuring the velocity on SPT rods was not available. It is the maximum of the integral of the square of the force divided by the impedance, over the whole record, and is based on the theoretical proportionality between force and velocity along most of the first 2L/c period on SPT energy tests. In real practice this proportionality is hard to achieve due to non-uniformities along the rod, imperfect joints, etc. Other factors also affect the accuracy of this method, so several correction multipliers had to be used. It was later recognized that these correction methods did not yield reliable results (please refer to the Appendix on ASTM D4633-05 for further information). EF2 is therefore generally inaccurate and obsolete, and should not be used . EF0 is the same as EF2. The E2F method does the same computation as EF2, but stops the integration at 2L/c. It has the same lack of accuracy as EF2. EV2 is the maximum of the integral of the square of the velocity multiplied by the impedance, over the whole record. It is based on the same proportionality principle as EF2, so it suffers from the same lack of accuracy.
The SPT Analyzer is compact and extremely rugged. An instrumented section of SPT rod measures strain and acceleration with each hammer blow. The SPT Analyzer then calculates the amount of energy transferred to the rod by the force and velocity measurements. Operation is straightforward: insert the special instrumented section of the SPT rod at the top of the drill string between the hammer and the existing sampling rods. Connect it by a cable to the SPT Analyzer. As the SPT test proceeds, the instruments obtain force and velocity measurements, and the energy transferred by the hammer to the rod is immediately displayed on the SPT Analyzer screen. Results are post processed and printed with the PDA-W software. The SPT Analyzer is rugged and endures harsh construction conditions. All equipment and analysis conform to ASTM D6066.