Effect of Microstructure Deficiency on Quasi-static and Dynamic Compressive Strength of Crystalline Rocks

Abstract

Grain size and microdeficits control static and dynamic behavior of crystalline rocks. Therefore, characterization and evaluation of the impact of such intrinsic parameters on mechanical behavior of rocks are necessary. Two marble stones of Baghat and Maroon in Iran, which consist of a unique mineral composition but different microstructural features, were selected as test samples. Microstructures of rocks were characterized using different techniques such as scanning electronic microscopic, fluorescent replacement and polarization microscopic techniques. A number of both rock types with different sizes were prepared and subjected to quasi-static and dynamic loading by a split Hopkinson pressure bar under different strain rates conditions, and mechanical properties of both marbles were measured. Microscopic studies about microstructure deficits show that fractal dimension in Maroon marble is higher than in Baghat marble. The results also show that the dynamic strength in both marbles is higher than their static strength. Strain rate controls mechanical properties in both rock types; however, in Baghat marble with a relatively lower microstructure intensity, this phenomenon is more significant. With increasing sample volume, dynamic strength of rocks is decreased. Morphology study of fracture surface in microscale indicated that in dynamic loading the intensity of created microcracks particularly intercrystalline microcracks is increased compared to the quasi-static loading condition.