Effect of 3D-printed polymer with negative Poisson's ratio structure on the mechanical characteristics of cemented tailings backfill

In underground mining environments, the structural instability of cemented tailings backfill (CTB), primarily attributed to brittle fracture behavior, represents a critical safety concern. This research utilized 3D-printed negative Poisson's ratio structural (monomeric, combined, and nested configurations) polymers to improve the brittle fracture resistance of CTB. Uniaxial compression tests, acoustic emission, and scanning electron microscopy were conducted to systematically evaluate the influence of negative Poisson's ratio polymers with different structures on the strength, toughness, stress-strain response, internal damage processes, and microstructural characteristics of CTB. Experimental results showed that using the monomeric configuration negative Poisson's ratio polymer in CTB slightly reduced its strength, while combined and nested configurations increased strength by 27.01 % and 30.66 %, respectively. The post-peak load-carrying capacity and toughness of polymer-reinforced CTB were improved. Specimens reinforced with combined and nested configurations of negative Poisson's ratio structural polymers exhibited superior energy absorption capacity and better internal damage evolution mechanisms, enabling synergistic enhancement of strength and toughness. The cracks in normal CTB were tensile, whereas the cracks in polymer-reinforced CTB were mainly a combination of tensile and shear cracks. The strengthened specimens demonstrated a decreased cumulative number of acoustic emission events and a postponed occurrence of macroscopic crack propagation. The polymer lattice and matrix achieve stress transfer through mechanical interlocking, but microporosity defects in both materials and the weakening effect of polymer doping on matrix integrity together restrict the composites' mechanical properties. This study not only proposes an innovative approach to address the brittle fracture issue of CTB in underground mining environments, but also significantly enhances mining safety while advancing sustainable development within the industry.