Research on the mechanical properties and micro damage mechanism of water bearing sandstone under uniaxial compression

To provide a theoretical basis for the development of water hazard prevention schemes for roof sandstone, this study systematically conducts uniaxial compression, acoustic emission, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD) tests on the thick water-bearing sandstone at depths of 623-943 m in the Luohe Formation of the Binchang Mining Area, investigating its mechanical properties and the mechanisms of micro-damage evolution under uniaxial compression.The results indicate that with the increase in water content, the elastic modulus, strength, peak strain, and brittleness index of sandstone decrease. Dry sandstone primarily undergoes shear failure, while water-saturated sandstone mainly experiences a combination of tensile and shear failure. The cumulative ring count of acoustic emission in water-saturated sandstone decreases with increasing water content, and the damage evolution can be divided into three stages: the initial damage stage, the stable damage development stage, and the rapid damage increase stage. The damage variable of water-saturated sandstone increases with the rise in water content. The uniaxial compression fracture characteristics of dry and saturated sandstone include intergranular and transgranular fractures, primarily exhibiting brittle failure. In dry sandstone, the contents of Si, Fe, Ca, Na and Al are relatively high, while in water-saturated sandstone, these contents decrease, but the Carbon(C) content significantly increases. The average grain size of saturated sandstone is smaller than that of dry sandstone, and the strength of sandstone decreases with the reduction in grain size.The main components of sandstone include feldspar, calcite, muscovite, and quartz, among these, quartz endows the sandstone with higher strength, and the strength of the sandstone decreases with a reduction in the quartz content.