Effect of particle shape on the response of geogrid-reinforced systems: Insights from 3D discrete element analysis

Understanding soil-geogrid interaction is essential for the analysis and design of reinforced soil systems. Modeling this interaction requires proper consideration for the geogrid geometry and the particulate nature of the backfill soil. This is particularly true when angular soil particles (e.g. crushed limestone) are used as a backfill material. In this study, a three-dimensional (3D) discrete element model that is capable of capturing the response of unconfined and soil-confined geogrid material is developed and used to study the response of crushed limestone reinforced with geogrid and subjected to surface loading. The 3D shape of the crushed limestone is modeled by tracing the surface areas of a typical particle and fitting a number of bonded spheres into the generated surface. Model calibration is performed using triaxial tests to determine the microparameters that allow for the stress-strain behaviour of the backfill material to be replicated. To demonstrate the role of particle shape on the soil-geogrid interaction, the analysis is also performed using spherical particles and the calculated response is compared with that obtained using modeled surfaces. The biaxial geogrid used in this study is also modeled using the discrete element method and the unconfined response is compared with the available index test results. This study suggests that modeling the 3D geogrid geometry is important to accurately capture the geogrid response under both confined and unconfined conditions. Accounting for the particle shape in the analysis can significantly enhance the predicted response of the geogrid-soil system. The modeling approach proposed in this study can be adapted for other reinforced soil applications.