Effect of Particle Morphology on the Deformation Behavior of Sand under Monotonic Loading Conditions

When a projectile hits sand, the projectile places high stresses on the sand surface. Granular materials at high stresses are liable to crushing. The pressure at which crushing occurs depends greatly on particle shape and relative density. These parameters also greatly influence the changes in particle shape and size after crushing. Additionally, projectiles fired at extremely high velocities are preceded by a pressure wave. This pressure wave can crush granular material before the projectile ever touches the surface. If the sand has been crushed and its inherent particle properties changed before projectile impact, the projectile may not behave as expected. Therefore, it is imperative to understand a wide variety of strength parameters in order to understand the mechanics of sands with different morphology.

Furthermore, when performing experiments to obtain strength parameters, it is important to understand the limitations of these experiments. Particle size distribution methods such as standard sieve tests, imaging analysis, and light scattering techniques all involve a level of bias particle size bias in the data acquisition process. Additionally, standard triaxial testing assumes constant strain throughout the specimen based on overall displacement of the specimen during testing. This is an invalid assumption as strain localization occurs very early during testing and causes strain concentrations near the center of the specimen.