Abstract
Micromechanical modeling of geomaterials is challenging because of the complex geometry of discontinuities and potentially 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 of 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 (1) large displacements and/or deformation, (2) the process of high stress accumulated at contact areas, (3) the failure of a mineral cemented rock samples under high stress, and (4) post-failure fragmentation. The analysis highlights the importance of accurately capturing (1) the sequential evolution of geomaterials responding to stress as motion, deformation, and high stress; (2) large geometric features outside the norms (such as large asperities and sharp corners) as such features can dominate the micromechanical behavior; and (3) different mechanical behavior between loosely packed and tightly packed granular systems.
Highlights
Numerical modeling of microscale mechanical behavior of geomaterials is of great importance for understanding and predicting material constitutive and geomechanical behavior at larger scales in subsurface engineering activities such as unconventional hydrocarbon production [22], nuclear waste disposal [23], and CO2 sequestration [21]
Though discrete element method (DEM) is designed for computation of discontinuous bodies with dynamic contacts, the assumption of rigid bodies, the use of explicit time iteration, and the limitation of interpolation fields for continuum mechanics limit its accuracy for dealing with realistic geometric features or dynamic contacts
We present development of an approach with rigorous treatment of dynamic contacts in deformable geomaterials for microscale mechanical analysis based on the numeral manifold method (NMM)
Summary
Numerical modeling of microscale mechanical behavior of geomaterials (soils and rocks) is of great importance for understanding and predicting material constitutive and geomechanical behavior at larger scales in subsurface engineering activities such as unconventional hydrocarbon production [22], nuclear waste disposal [23], and CO2 sequestration [21]. Numerical modeling of mechanical processes in geomaterials at the microscale is challenging because of the computational geometry associated with (1) complex evolving geometric features that are discontinuous, and (2) multiple deformable material bodies with dynamic contacts. Though DEM is designed for computation of discontinuous bodies with dynamic contacts, the assumption of rigid bodies, the use of explicit time iteration, and the limitation of interpolation fields for continuum mechanics limit its accuracy for dealing with realistic geometric features or dynamic contacts. We present development of an approach with rigorous treatment of dynamic contacts in deformable geomaterials for microscale mechanical analysis based on the NMM.
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