Mechanical properties and meso-structure response of cemented gangue-fly ash backfill with cracks under seepage- stress coupling

Abstract

Seepage and cracks are two important factors affecting the stability of the cemented gangue-fly ash backfill (CGFB, a mixture of coal gangue, fly ash, cement and water). In this study, the CGFB samples with a 45° single crack were prepared and the mechanical properties of CGFB with cracks under different seepage water pressures were studied. Based on the theory of damage mechanics, the damage variable which can evaluate the seepage effect and crack effect was introduced, and the damage evolution law of CGFB with cracks under the seepage-stress coupling was discussed. The research hat: The mechanical properties of CGFB with cracks under seepage-stress coupling are mainly determined by the seepage water pressure, prefabricated crack and their coupling effects. Seepage and crack aggravate the attenuation of the peak strength and elastic modulus of CGFB, but with the increase of seepage water pressure, the deterioration effect of the crack weakens. Seepage and crack have significant effects on the damage of CGFB. Finally, based on the discrete element software, damage mechanism of CGFB with cracks under seepage-stress coupling was analyzed from a microscopic perspective. The research results can lay a foundation for the long-term stability analysis and instability prediction of CGFB with geological defects such as joints and cracks in water-rich mines.