The current geotechnical design practices often rely on Standard Penetration Test-N (SPT-N) values without conducting additional, costly laboratory tests. To enhance the reliability of these values, an investigation into the hammer efficiency from various drilling rigs employed by the TMR Geotechnical Section has been undertaken. Utilising the latest Standard Penetration Testing (SPT) Analyzer, this research aims to measure and analyse the hammer efficiency.
Preliminary findings reveal a notable disparity between automatic and manual hammers. The automatic hammers demonstrate a higher energy output (approximately 85%) compared to manual counterparts (around 60%). This highlights the need for caution when utilising SPT-N values established using manual hammers in previous years, as the correlations of soil properties may differ when adapting to the current automatic hammer technology.
Notably, while Australia employs uncorrected SPT-N values, many other countries use corrected values. Therefore, it is critical to consider correlations established in those countries when adopting SPT-N values obtained from automatic hammers. Failure to do so may result in an underestimation of soil properties, potentially leading to a conservative design approach.
This presentation explores a comparative analysis of the efficiency of hammers used by various drilling rigs. This study is crucial for ensuring the dependability of geotechnical design methodologies, considering advancing drilling technologies.
