Effects of inhomogeneity on mechanical properties of granites in Songliao Basin using the grain-based model

The macroscopic mechanical properties of granites are affected by inhomogeneous factors such as mineral shape, size, and distribution. Microscopic parameters of granites from the Songliao Basin were calibrated in PFC 2D using the grain-based model approach. The effects of mineral grain size on strength, deformation, and microcracking behavior were analyzed by conducting the uniaxial compression test and triaxial compression test under confining pressure of 50 MPa. Research showed that the strength of the rock gradually reinforced as the grain size increased and was positively correlated with the average grain-disk size ratio of 2.5~16.87. The results of numerical simulations on grain size effects conflicted with the results obtained in laboratory experiments. To reflect the true mechanism of the grain size effect, the relative percentage method of microscopic strength parameters was proposed, and the strength variation law after the discounted reduction matched well with the conclusion of the laboratory test, indicating that the method has considerable feasibility. Research on the microscopic parameters of granites will be of great guidance for geothermal research in the Songliao Basin.