Study on the mechanics performance and deformation characteristics of polypropylene fiber-reinforced solid waste-based fill material

To more rationally and effectively handle and utilize solid wastes, this study explored the preparation of superior performance green backfill materials under alkaline activation conditions. Using waste stone limestone powder (LP), slag powder (SP), and fly ash (FA) as cementitious materials, coal gangue (CG) as fine aggregate, and incorporating polypropylene fibers (PP) of different lengths and contents, a ternary solid waste-cemented coal gangue green backfill material (LSFCLs + Ps) was developed. The mechanical properties and deformation characteristics of LSFCLs + Ps were investigated through splitting tensile strength (STS) tests, uniaxial compression strength (UCS) tests, digital image correlation (DIC), and scanning electron microscopy-energy dispersive spectroscopy (SEM–EDS). The results indicate that: (1) When the fiber length is 9 mm and the content is 0.3%, the STS and UCS reach optimal values of 1.05 MPa and 7.53 MPa, respectively, which are 56.72% and 45.93% higher than those of the control group. (2) The addition of PP enhanced the deformation resistance of LSFCLs + Ps, improved the efficiency of elastic strain energy conversion, and reduced the energy consumption ratio of the backfill. (3) The effective bonding of PP with hydration products improved the overall density of the samples, inhibiting the formation and propagation of internal cracks. The research findings provide a theoretical basis for the treatment of coal gangue and the development of new backfill materials in mining areas.