Mechanical and Civil Engineering Seminar

The Department of Defense (DoD) operates military aircraft on soil surfaced airfields that are generally constructed of angular granular material (i.e., sand and gravel) produced by rock crusher operations. Aircraft tire interaction, with such discontinuous granular material, can produce large deformations that result in rutting of the surface. When large ruts form on runways, military aircraft can no longer operate safely on them. The discrete element method (DEM) is capable of modeling flow and deformation of granular material, which makes it well suited to simulate this soil-tire interaction problem. I will present a numerical study of the effect of aircraft wheel load (in the form of a circular steel plate) on cohesionless soil that is modeled as dilated polyhedral DEM particles. The goal of the study is to better understand deformation of realistic shaped granular material under loading to develop improved guidance for soil surfaced airfield design and evaluation. As a follow up to the soil-tire interaction work, we are developing a dilated polyhedral DEM fracture model. It is well known that fracture of sand particles plays a role in granular material response to loading at large stresses (>5 MPa) and to high strain rate loading (102 - 107 s-1). The macroscale response is dependent on grain scale interactions. There are experimental limitations to analyzing the grain scale behavior of sand particles, so the DEM can serve as a substitute to experimental work at this scale. Simulations with the dilated polyhedral DEM fracture model will provide increased knowledge of the influence of grain fracture on macroscale response which could improve design of penetrating munitions and protective soil embankments.