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Discrete Element Method (DEM) is a numerical technique that uses particulate mechanics in simulating the discontinuous behavior of particulate materials. DEM presents the advantage of modelling those materials in a particulate level allowing specifications of particle geometry including how their contacts interact. However, identifying microparameters that can accurately simulate the behavior of particulate materials is challenging. This paper presents the calibration of the microparameters of materials used in an earthfill dam that experienced slope movements. The main components of the earthfill dam under study were clay, for the core and blanket, and rockfill materials, for the protective shell. Linear parallel-bond model (LPBM) was used to describe the interactions between clay particles. Microparameters involved with the LPBM were particle stiffness, friction coefficient, bond strength, and bond stiffness. A triaxial test DEM model was developed to calibrate the clay microparameters, and it was successful in simulating the measured macroscopic peak and critical state behavior of clay materials. Rolling resistance linear model was used to describe the interactions between rockfill particles. Microparameters associated with the rolling resistance linear model were particle stiffness, friction coefficient, and rolling resistance coefficient. Large-scale direct shear test was simulated to calibrate rockfill microparameters, and it was able to capture the measured macroscopic shear behavior of rockfill materials. Calibration methodologies performed were successful in identifying appropriate microparameters for both rockfill and clay materials. The calibrated microparameters are beneficial in the development of a DEM model that can analyze movements and landslides in the vicinity of the earthfill dam or other earthfill dams built with similar materials.

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The morphological features of fossorial animals have continuously evolved in response to the demands of survival. However, existing methods for animal burrowing mechanics are not capable of addressing the large deformation of substrate. The discrete element method (DEM) is able to overcome this limitation. In this study, we used DEM to develop a general model to simulate the motion of an animal body part and its interaction with the substrate. The DEM also allowed us to easily change the forms of animal body parts to examine how those different forms affected the biomechanical functions. These capabilities of the DEM were presented through a case study of modeling the burrowing process of North American Badger. In the case study, the dynamics (forces, work, and soil displacements) of burrowing were predicted for different forms of badger claw and manus, using the model. Results showed that when extra digits are added to a manus, the work required for a badger to dig increases considerably, while the mass of soil dug only increases gradually. According to the proposed efficiency index (ratio of the amount of soil dug to the work required), the modern manus with 5 digits has indeed biomechanical advantage for their fossorial lifestyle, and the current claw curvature (25.3 mm in radius) is indeed optimal. The DEM is able to predict biomechanical relationships between functions and forms for any fossorial animals. Results can provide biomechanical evidences for explaining how the selective pressures for functions influence the morphological evolution in fossorial animals.