Rod effects on transferred energy into SPT sampler using smart measurement system

Abstract

To improve the accuracy of the standard penetration test (SPT) results, smart measurement system, which considers the energy transfer ratio into the sampler (ETR<sub>Sampler</sub>), is required. The objective of this study is to evaluate the effects of joints and rod length on the transferred energy into the sampler. The energy transfer ratios into the rod head (ETR<sub>Head</sub>) and ETR<sub>Sampler</sub>, and the energy ratio from the head to the sampler (ER<sub>HS</sub>) were obtained using energy modules, which were installed at the rod head and above the SPT sampler. Linear regression analyses are conducted to correlate the ER<sub>HS</sub> with the number of joints, rod length, and SPT N-values. In addition, the dynamic resistances are calculated using both transferred energies into the rod head and into the sampler, and are compared with the corrected cone tip resistance measured from the cone penetration test (CPT). While the ETR<sub>Head</sub> are generally constant, but the ETR<sub>Sampler</sub> and ERHS gradually decrease along the depth or the number of joints, except at certain depths with high SPT N-values. Thus, the ER<sub>HS</sub> can be estimated using the number of joints, rod length, and SPT N-values. The dynamic resistance evaluated by E<sub>Sampler</sub> produces a better correlation with the corrected cone tip resistance than that by E<sub>Head</sub>. This study suggests that transferred energy into the SPT sampler may be effectively used for more accurate subsurface characterization.