CPT-Informed Model for Rapid Penetration into Sand

Results of rapid projectile impact experiments on sand are described, from which a phenomenological penetration model is developed. Projectiles are launched in a gravity-aligned configuration into dry and partially-saturated sand at an impact velocity of approximately 200 m/s. The velocity-time history of penetration is resolved using an optical measurement technique known as photon Doppler velocimetry (PDV). Soil resistance to penetration is found by single differentiation of the velocity-time data. Experiments suggest the existence of at least two penetration regimes separated by a stress of approximately 25 MPa. At high velocities, penetration involves intense particle crushing, whereas low velocity penetration is facilitated through particle rearrangement and localized shear failure. High velocity penetration is inefficient, and the majority of penetration occurs at lower velocities. Saturation reduces penetration resistance, particularly in denser soils. These observations are used to inform the development of the semi-analytical GeoPoncelet model, which, along with CPT tip stress, are used to directly predict the response and depth of burial or projectiles in sand with high accuracy.