The Effect of Grain Size Heterogeneity on Mechanical and Microcracking Behavior of Pre-heated Lac du Bonnet Granite Using a Grain-Based Model.

The effect of grain size heterogeneity on the mechanical and microcracking behavior of Lac du Bonnet (LdB) granite during heating, cooling, and uniaxial compression loading is investigated using a grain-based model. By defining a grain size heterogeneity index H, the heterogeneity induced by variation of grain size distribution can be explicitly incorporated into the grain-based model quantitatively. Five modelled LdB granite samples with different grain size heterogeneity indices ranging 0.19–1.22 are established. The results suggest that the grain size heterogeneity and treatment temperature have critical impacts on the mechanical properties of modelled LdB granite samples. With the increase of temperature and grain size heterogeneity index, the mechanical properties show a decreasing trend. Several empirical formulations are developed to predict the temperature-dependent mechanical properties of modelled LdB granite samples with different grain size heterogeneity indices. Generally, modelled LdB granite samples with greater grain size heterogeneity index has a lower temperature of brittle-ductile transition. In terms of microcracking behavior, both temperature and grain size heterogeneity affect it, including number, density, orientation, and distribution. As the temperature increases, the number and related density of thermal stress-induced cracks increase. Generally, the amount of thermal stress in modelled LdB granite samples during heating increases with the increases of grain size heterogeneity index. The controlling factor of the failure pattern of samples gradually changes from the presence of thermal stress-induced cracks to grain size heterogeneity as the model progresses from relatively homogeneous (H ranging 0.19–0.76) to heterogeneous (H ranging 0.93–1.22). Highlights: Explicitly incorporate grain size heterogeneity induced by grain size distribution into a grain-based model. Reveal the effect of grain size heterogeneity on mechanical properties and microcracking behavior of Lac du Bonnet granite at different temperatures. Propose empirical formulations to quantify the temperature-dependent mechanical properties of Lac du Bonnet granite with grain size heterogeneity index. [ABSTRACT FROM AUTHOR]