Investigation into Effect of Sonic Drilling Methodology on Standard Penetration Test Results in Dense Sand

An extensive field investigation was conducted to quantify the variation between drilling methodologies on the SPT outputs (SPT-N-60 values) in dense saturated sands. For this experiment, a test site with reasonably consistent soil properties was identified, where multiple standard penetration tests (SPTs) were conducted using four drilling methodologies, including rotary core, direct push, and two sonic drilling methods. Considering the rotary core as the benchmark, the SPT-N values obtained from this method were systematically compared with those from the other three drilling methodologies. For the dense saturated sands studied in this research, the SPT-N values from rotary sonic DT-45 showed the closest correlation to the SPT-N values from the rotary core, with about 15% variation. The variation was shown not to be statistically significant, considering the inherent variability of the SPT and the measured confidence interval of the SPT-N values from the standard rotary core method.