Abstract
Micro-indentation tests were performed adopting the grid-type of analysis on two types of shale rocks, which are porous natural materials characterized by strong geological structural and microfabric features. Emphasis was placed on understanding the influence and linkage between these microstructural-microfabric characteristics and the mechanical properties obtained from indentation, including hardness, modulus, elastic and plastic deformation fractions, and their anisotropic and heterogeneous distribution. The indentation loading-unloading curve patterns also functioned as a way to explore this linkage besides the global variation in the mechanical properties. Statistical tools and machine learning techniques were further employed in the indentation data analysis, providing a means of quantifying the intricacies involved with the mechanical properties of the shales. The creep behavior of these porous materials was quantified and linked to the anisotropic structure and mechanical properties, providing insights into one of the most complex natural materials, as many researchers have characterized. Opposite to previously published data on transversely isotropic shale rocks with vertical axis of symmetry, especially shales with high clay and organic content, the results in the present study showed higher modulus normal to the bedding planes compared to the parallel direction, which observation was attributed to the low clay (and organic) content of the shales and the possible low depth the shales were obtained.
NSTL