Multiscale mechanical behavior of the Qiongzhusi Formation shale

The Qiongzhusi Formation shale has attracted significant attention due to its vast mining potential; its macroscopic failure behavior is fundamentally governed by its microstructural characteristics and compositional evolution. This study employs a combined approach of laboratory testing and theoretical analysis to investigate the cross-scale mechanical correlations of the Qiongzhusi Formation shale. First, the mineral composition of the Qiongzhusi Formation shale was determined through XRD testing. Next, nanoindentation tests were conducted to obtain the mechanical properties of the minerals, and a Gaussian probability-based mineral deconvolution classification method was proposed to classify the nanoindentation dataset based on mineral mechanical properties. Finally, the macro- and micro-scale mechanical properties of the Qiongzhusi Formation shale were correlated using the Mori-Tanaka method. The results indicate that: (1) XRD mineral composition analysis revealed that the Qiongzhusi Formation shales exhibit high hardness and high brittleness; (2) the Nanoindentation curves of different minerals vary significantly; framework minerals such as quartz demonstrate strong brittle energy storage characteristics, whereas muscovite exhibits an extremely high proportion of plastic work; (3) A Gaussian probability-based mineral deconvolution classification method proposed in this paper can effectively classify minerals in Nanoindentation datasets based on their mechanical properties. (4) The macroscopic elastic modulus of shale exhibits significant sensitivity to changes in muscovite content, and an increase in quartz content significantly enhances the mechanical properties of the Qiongzhusi Formation shale. Furthermore, by integrating environmental geology with sustainable development needs, multiscale analysis techniques can reveal the mechanical response mechanisms of minerals and rocks under complex environmental conditions, thereby further expanding their application prospects in shale gas exploration and development engineering.