Effect of mineral materials heterogeneity on rock failure: insights from a uniaxial compressive test of sandstone by in-situ x-ray computed tomography

This study explores the mechanism of sandstone crack initiation and propagation considering mineral heterogeneity using an integrated in-situ X-ray micro-tomography (CT), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDS) approach. Uniaxial compression tests were performed on sandstone samples with rectangular 10 mm × 10 mm × 5 mm under in-situ X-ray micro-tomography monitoring. Initial state, elastic deformation, plastic deformation and post-failure state with load 0 N, 380 N, 945 N and a destroyed state are scanned for CT slices. SEM and XRD are employed to verify the mineral materials with CT slices. The microcrack initiation and propagation to coalescence as macrocrack are discussed with mineral materials heterogeneity. The results show that: (1) two types of crack regions in the sandstone near failure based on the porosity variation. The cracks in the porous-rich region are more prone to propagation along initial flaws, while the cracks in the dense area are more prone to initial and propagate in the mineral boundaries by contact stress. (2) The macroscopic cracks evolution process starts from the original cracks, and with the mineral materials contact force in dense area transferred, transmitted, the initial crack propagation and interaction with stress-induced cracks until coalescence. Contact force transmits at the micro level, resulting in macroscopic cracks and rock failure. The novelty of this work lies in linking micro-mineral compositional variations with macroscopic crack evolution under controlled uniaxial compression. The findings offer new insights into predicting crack propagation paths in heterogeneous rocks and provide valuable data for developing numerical models for rock stability assessment.