Quasi-Static to Dynamic Transition During Horizontal Intrusion in Granular Media

Intrusion in granular media is of great importance for a range of applications spanning tunneling, animal and robotic locomotion, impact, and cratering. In the quasi-static regime, intruder forces are largely velocity-independent and can often be described using local, grain-scale models. At high speeds, inertial and nonlocal effects become significant, and intrusion forces follow Poncelet-type models. The mechanisms governing the transition between these regimes remain poorly understood, and the link between intruder velocity, depth, and forces has not been established. In this work, we use discrete element method simulations to study the particle-scale mechanisms that control the drag and lift forces acting on the intruder as a function of velocity, and depth, identifying the transition between quasi-static and dynamic regimes.