Microscale Mechanical Modeling of Deformable Geomaterials With Dynamic Contacts

Abstract:

Microscale mechanical modeling of geomaterials is challenging because of the complex geometry of discontinuities and potentially a large number of deformable material bodies that contact each other dynamically. In this study, we have developed a numerical approach for micromechanical analysis of deformable geomaterials with dynamic contacts. In our approach, we detect contacts among multiple blocks with arbitrary shapes, enforce different contact constraints for three different contact states (separated, bonded and sliding), and iterate within each time step to ensure convergence of contact states. With these features we are able to simulate the dynamic contact evolution at the microscale for realistic geomaterials having arbitrary shapes of grains and interfaces. We demonstrate the capability with several examples, including a rough fracture with different geometric surface asperity characteristics, settling of clay aggregates, compaction of a loosely packed sand, and failure of an intact marble sample. With our model, we are able to accurately analyze large displacements and/or deformation, the process of high stress accumulated at contact areas, the failure of a mineral cemented rock samples under high stress, and post-failure fragmentation. The analysis highlights the importance of accurately capturing: the sequential evolution of geomaterials responding to stress as motion, deformation and high stress; large geometric features outside the norms (such as large asperities and sharp corners can dominate the micromechanical behavior; and different mechanical behavior between loosely packed and tightly packed granular systems.