Soft Earth Geophysics

Understanding the complex mechanical behaviors of real-world granular materials is important for understanding the locomotion of animals and robots on granular substrates. In this work, we study the mechanical response of several desert sand samples collected from desert habitats of a species of bipedal hopping rodents called Jerboas (family Dipodidae). A combination of scanning electron microscopy and X-ray micro-computed tomography were used to characterize the particle morphology and size distributions, which were then incorporated into Discrete Element Method (DEM) simulations using multispheres to represent irregular particles. In both simulations and lab experiments, the yield strength of the sand samples was measured in shear tests under various confining pressures, which showed the sand samples with a mixture of individual particles and clumped particles to demonstrate high strength at a low density. We further relate this observation to the microscopic packing structure and particle shapes, and discuss its implications for the locomotion of the Jerboas.