Calibration of the GeoPoncelet Penetration Model for Conical Rod Projectiles in Cohesive Soils

Abstract

This study contributes to the limited data on available dynamic penetration in cohesive soils at velocities exceeding 100 m/s, in support of envisioned soil remediation of unexploded ordnances (UXOs) found at formerly used defense sites (FUDS). Cylindrical rod projectiles were launched at speeds between 140 and 200 m/s into large clayey sand targets carefully prepared at three water contents spanning the plastic range of the target material. Targets were statically compacted using a hydraulic press and identical specimens were prepared and probed using a commercial cone penetration test (CPT) cone adapted for laboratory testing. High-fidelity velocity-time records of rapid penetration were captured using a two-channel photon Doppler velocimeter (PDV), complemented by high-speed video and postmortem cavity castings. These impact tests, characterized by large strains and high strain rates, were correlated with conventional in situ CPT measurements to calibrate a novel semiempirical GeoPoncelet mathematical model. The model describes dynamic penetration resistance as a composite of drag and bearing stresses. Drag coefficients are reported using the PDV measurements for the tested soils, while bearing stresses were related to CPT tip resistance using a rate factor. The approach enables determination of the depth of burial (DoB) and penetration resistance of UXOs based on in situ measurements.