Numerical simulations of the mechanical behavior of soils for different grain shapes with the discrete element model

In granular sandy soils, micro-scale properties such as grain shape and grain inclination have an effect on soil behavior at the macro scale. There are very valuable experimental studies in the literature on the effects of micro properties on macro-scale soil properties. However, these experimental studies are limited and have been conducted under specific conditions. In this study, a monotonic triaxial test sample containing platy and spherical grains was numerically modeled using the discrete element method. The effects of platy grain orientation on macro-scale soil properties were investigated through the numerically modeled triaxial test. The diameter ratio of platy and spherical grains in the model was set to 4. Initially, numerical model parameters such as the effective modulus (E), stiffness ratio (kr), and friction coefficient (µ) were calibrated to match the laboratory test results. The effective modulus (E), stiffness ratio (kr), and friction coefficient (µ) values were determined as 2×10⁷, 1.08, and 0.30, respectively. The effects of platy grain orientation at 45°, 60°, 220°, and 340° (elevation and tilt angles) on macro-scale behavior were investigated using the determined calibration parameters. As a result of the analyses conducted using discrete element numerical models, it was observed that platy grain orientations could cause a 9–10-degree variation in the internal friction angle at the macro scale.