SPT Energy Measurements: Manual vs. Automatic Hammer Release

摘要

The results of SPT measurements performed at five locations in Greece with varying stratigraphy, using manual or automatic hammer release along with ~900 recordings of the impact energy transmitted to the string of rods, are presented. The measured values of energy ratio (ER) and associated uncertainty (standard deviation, a, and coefficient of variation, COV) are the first to be reported regarding the Greek practice of test. The results were analyzed in terms of hammer release technique, depth, soil type and blow count (N_(SPT)) and they were compared to pertinent published results. It was found that the ER and related uncertainty values depend mainly on the hammer release technique, and the following values are proposed for practical use under soil conditions similar to the ones encountered in the present study: ER_(man). = 46 ± 3.8 and ER_(auto) = 77 ± 4.6.