Meso-mechanical Damage and Energy Dissipation Mechanism in Backfill: Effects of Seepage and Crack Defects.

To study the meso-mechanical characteristics and energy dissipation mechanism of damage and failure of cemented backfill with cracks under seepage-stress coupling, the discrete element numerical test was used to explore the influence of axial stress, seepage water pressure and crack defects on the distribution of particle contact force chain and the development of microcracks in backfill, and the energy dissipation mechanism was expounded. The research shows that: ① With the increase of axial stress, and the particle contact force increases. The more elastic strain energy is released when the sample is destroyed, the greater the damage degree is, and the more cracks are developed. ② With the increase of seepage water pressure, the comparison of the strong and weak force chains is more and more obvious, the degree of stress concentration is intensified, and the cemented backfill specimen is more likely to yield failure. ③ The crack defects change the distribution law of the contact force chain inside the cemented backfill sample during the compression process. The contact force at the end of the crack is more concentrated, and the microcracks are generated, expanded and penetrated at the end of the crack. ④ With the increase of seepage water pressure, the boundary energy, bond energy and strain energy decrease gradually, and the energy absorption and storage capacity of cemented backfill samples decrease, while the friction energy shows an increasing trend. Compared with intact cemented backfill sample, the boundary energy, bond energy and strain energy of the cracked sample are reduced. The research results provide theoretical basis for the stability analysis and instability prediction of filling materials in deep water rich mines. [ABSTRACT FROM AUTHOR]