Mechanical Properties, Failure Modes, and Damage Development of Stratified Cemented Tailings Backfill under Uniaxial Compression

Layered cemented filling leads to a layered composite structure of cemented tailings backfill (CTB) composed of high-strength top and bottom layers, as well as a low-strength middle layer. To solve the problem of the low mechanical properties of the middle layer caused by layered filling, this study proposes the concept of an enhance layer, that is, an enhance layer is added to the middle weak layer to improve its overall mechanical properties. To explore the characteristics of strength, failure modes, energy dissipation, and progressive damage of stratified cemented tailings backfill (SCTB) with varying layered structures, the uniaxial compressive tests of SCTB specimens with enhance layers c/t of 1:15, 1:10, and 1:6, as well as height proportions of 0.1, 0.2, and 0.3, are examined. The results show that the elastic modulus and uniaxial compressive strength (UCS) of SCTB samples increase with the height ratio and cement-to-tailings ratio of the enhance layer. The elastic modulus and strength of SCTB specimens is more sensitive to the height ratio of the enhance layer than the c/t ratio. Moreover, the SCTB specimens mainly manifested as tensile failure of the upper layer and lower layer, but they did not penetrate the entire specimen. The propagation of cracks is limited by the addition of the enhance layer. The SCTB specimens have stronger plastic deformation ability, and a large part of the all-strain energy is dissipated in the shape of plastic failure. In addition, a constitutive model for damage in SCTB samples has been developed. The SCTB samples with a reasonable structure can also achieve sufficient strength compared to directly increasing the c/t ratio of CTB specimens while reducing the cost of cemented tailings backfill preparation. This approach reduces the carbon footprint of the mining industry and improved the overall mechanical properties and stability of the stratified cemented tailings backfill. This study provides a new approach for high-stage subsequent stope backfilling. The findings will offer guidance for the design of a layered filling mining method.