Abstract: This paper highlights the potential of real-time borehole logging— commonly referred to as Measurement While Drilling (MWD)— for enhancing the interpretation of geotechnical parameters. An experimental campaign was conducted on approximately 100 boreholes across 30 project sites, with more than 90% of operations carried out using rotary drilling. While most sites were located in the Paris region, the study area spanned various regions across France, encompassing a range of geological conditions. The soils encountered included clay, gravel, compact sand, chalk, and limestone.
The study applied a modified version of the Somerton Index, combining push down force and penetration rate, to evaluate soil resistance. To improve the reliability of this index, a correction was introduced using calibration data obtained before and after drilling, accounting for variations in machine performance, sensor sensitivity, and drilling fluid temperature.
Data accuracy was assessed by comparing MWD-derived indices with standardized in-situ test results, primarily pressuremeter measurements. A strong linear correlation was observed between the corrected Somerton Index and the pressuremeter limit pressure, particularly in rotary-drilled boreholes, supporting the use of MWD data for soil characterization.
Preliminary findings suggest that the corrected Somerton Index can serve as a reliable predictive indicator of soil strength. The approach demonstrates both technical feasibility and cost-efficiency, reinforcing the value of MWD as a complementary tool in geotechnical site investigations.