Preliminary Study on the Potential of the Investigative Drilling (ID) Method for Quantitative Site Characterisation

Investigative drilling (ID) is a modern measurement while drilling (MWD) technique that has been effectively used in site investigations for several long corridor projects in Australia. The drilling data collected through the ID method has provided clients with valuable in situ strata verification for earthworks and footings. However, the use of drilling data from ID has been primarily qualitative. This paper presents a preliminary assessment of the ID method’s potential for quantitative site characterisation through case studies involving soils and rocks. Comparative analysis with conventional boreholes demonstrates that ID data provides significant insights into ground conditions and can be used to characterise soil and rock properties. Specifically, the penetration rate, as a single drilling parameter, proves effective in identifying rock fractures, while compound indices such as the soil-rock resistance, Somerton index, and drilling energy correlate with the standard penetration test (SPT) values and rock strength. Despite the promising results, further rigorous testing is necessary to validate these findings, given the inherent uncertainties in subsurface conditions and conventional testing results.