A nondimensional model for axial digging in granular materials

Abstract

We investigate the mechanics of thin diggers in a packing of granular materials. Experiments were conducted by pushing diggers of varying thickness into the granular packing and recording the force-depth data. The digger is modeled as a column in buckling; its column effective length factor is calculated. We solve two optimization problems. First, we limit the axial force the digger is allowed to experience and analytically solve for the maximum depth dug. This analysis is compared to experimental data. Second, we fix the digger's final depth and estimate the thickness that minimizes digging energy. A stochastic algorithm is proposed to model the digger's axial force as a function of depth, taking into account the force distribution at each depth. We then calculate the energy required for a digger of each thickness to reach a fixed depth and compare with experimental data.