Macro-meso damage and fracture model for determining the creep characteristics of shale under osmotic pressuresure

Abstract

disturbance of coal mining in water-rich environment can cause damage and rupture of surrounding rocks. In this study, using deep shale as the research object, a rock percolation-disturbance creep test rig has been developed to conduct triaxial compression tests for determining the creep characteristics of the shale under different disturbance parameters. Specifically, the effects of seepage pressure, disturbance amplitude, and disturbance frequency on the creep and meso-mechanical properties of shale are examined by scanning electron microscopy. The results show that with the increase in the disturbance amplitude, disturbance frequency, and seepage pressure, the number of macroscopic cracks on the shale surface increases, and the distribution and propagation mode of cracks become complicated. The sensitivity of the axial strain of shale to the disturbance amplitude, disturbance frequency, and osmotic pressure follows this order: osmotic pressure > disturbance amplitude > disturbance frequency. With the increase in the disturbance amplitude and frequency, many small block structures appear in the shale section, and the surface flatness decreases. However, with the increase in the osmotic pressure, the flatness of the shale section increases, and the section tends to be smooth. As the osmotic pressure increases, the fracture mode of shale is mainly transformed from single brittle fracture to a complex fracture mode of brittle fracture (dominant) and ductile fracture. A fractional nonlinear perturbation creep model of shale under osmotic pressure is established and its reliability and applicability is verified through the experimental results. Overall, the presented results can serve as theoretical reference for the prevention and control of mine water inrush disaster in water-rich areas.