Use of a portable measurement while drilling system for shallow subsurface characterization

Abstract

The Portable Measurement While Drilling (PMWD) equipment designed by CEREMA engineers is an innovative and lightweight tool to perform rapid assessment of shallow subsurface conditions. The equipment consists of sensors mounted on a cordless rotary drill that records depth, downforce, rotation, torque, and time. This paper presents results obtained with the portable MWD under laboratory and field conditions, which were directly compared to soil resistance profiles obtained with a lightweight dynamic cone penetrometer (LDCP – PANDA). Results from 66 PMWD profiles and 87 LDCP profiles demonstrated the potential applicability of the portable MWD in shallow subsurface investigations. A linear correlation between the Somerton Index (SD) and the LDCP tip resistance (qd) was obtained in granular soils under controlled conditions, ranging from sand (SP) to sandy gravel (GP). The obtained relationship was applied to MWD results from a 180-m long, 50-m tall grassy slope in New Hampshire, USA. It was observed that the estimated qd values from drilling parameters have a good correspondence with LDCP results at the same testing locations. Shallow subsurface characterization using MWD can potentially be used for shallow foundations, compaction control, pavement subgrade evaluation, and areas prone to geotechnical hazards not easily accessible through usual exploration methods.

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