use of a portable measurement while drilling system for shallow subsurface characterization
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A portable Measurement While Drilling (MWD) equipment designed by CEREMA engineers is an innovative, lightweight tool to perform rapid assessment of shallow subsurface conditions. The portable MWD consists of sensors mounted on a cordless rotary drill that record depth, downforce, rotation, torque, and time. Shallow subsurface characterization using MWD presents a high applicability, including shallow foundations, compaction control, pavement subgrade evaluation, and areas prone to geotechnical hazards and not easily accessible through usual means. This paper presents an assessment of material resistance and heterogeneity using the portable MWD in slopes where field rockfall experiments have also been performed. Several MWD profiles on different materials found along soil slopes and catchment ditches (e.g., sand, gravel) were compared to other portable geotechnical characterization tools (e.g., lightweight dynamic penetrometer and lightweight deflectometer). Results have demonstrated that drilling parameters can help describe subsurface conditions and evaluate material heterogeneity along different soil profiles. The measurements from this experimental campaign will provide a better description of potential rockfall impact zones, which will ultimately help improve existing rockfall models and their predictions of the rockfall kinematics produced from the complex interaction between the falling block and the ground.