An improved grain-based numerical manifold method to simulate deformation, damage and fracturing of rocks at the grain size level.

An improved grain-based numerical manifold method (NMM) is developed to investigate deformation and damage of intact rocks at the meso‑scale. The grain boundaries are embedded into the numerical manifold method using a random Voronoi tessellation technique to approximate the microstructure of rocks at the meso‑scale. To enhance efficiency, an improved contact loop updating algorithm is proposed, which only preserves the corners of polygonal blocks and deletes the rest of the loop boundary nodes, thus greatly reducing the number of loop nodes involved in contact retrieval. An interface contact model considering cohesion and tensile strength between rock grains is incorporated into the numerical manifold method to simulate fracturing. With the newly developed grain-based numerical manifold method, Brazilian tests and uniaxial compression tests are numerically simulated to validate failure pattern and macroscopic response against laboratory tests. Sensitivity analysis is conducted using the proposed model to further investigate the influence of different number of grains and different stiffness ratio on the macroscopic response of rocks. The results indicate that the improved grain-based numerical manifold method can be effectively used to study deformation, damage and fracturing of rocks at the meso‑scale. [ABSTRACT FROM AUTHOR]