An analysis of low velocity penetration of clay soils

Abstract

Recent interest in earth penetration has been stimulated by both military and civilian applications. Experimental programs in this area have advanced more than theoretical developments but neither analytical nor empirical prediction methods are satisfactory. This study is an approximate theoretical analysis of low velocity penetration (in the range of 100 fps) in clay soils. Based on experimental observation a function describing the soil's displacement field is assumed (in this case a pathline is parabolic). The soil is modeled as a nonlinear elastic material. A generalized coordinate describes the displacement field and is determined by Hamilton's Principle. The time dependent behavior of the projectile is determined by calculating the amount of the projectile's kinetic energy transferred to the soil as strain energy, potential energy, dissipative energy and kinetic energy in a small increment of time. This incremental computation procedure provides depth, velocity and deceleration vs time predictions for the projectile. Solutions were obtained for clays ranging from 50% saturation to 100% saturation. ...