Theory and practice of projectile's penetration in soils

Experimental studies of soil penetration by low-velocity projectiles stimulated the development of theoretical modeling of the phenomena. We developed a model of vertical penetration of granular soils verified by known experiments and dimensional analysis. The experimental results showed nonmonotonic dependence between projectile deceleration and depth of penetration. Net resistant force was found to be a complicated function of variable deceleration and depth. This force was defined not only with pure dynamic and static components, but also with a mixed component important for interpretation of experimental results. Theoretical analysis of nonmonotonic variation of resistance with depth permits evaluation of static properties of noncohesive material using dynamic characteristics of projectile penetration. An understanding of physical processes governing projectile's deceleration was acquired. Velocity and acceleration are obtained as functions of initial velocity, depth of penetration, and media properties. We show two conditions when peaks of acceleration are observed. The initial peak is due to dynamic characteristics, and the second peak is due to static characteristics of penetration.