Mechanical properties, deformation response, energy evolution and failure pattern of stratified cemented tailings backfill under triaxial compression

Abstract

The backfill should keep stable in the primary stope when mining an adjacent secondary stope in subsequent open stoping mining methods, and the large-size mined-out area is usually backfilled by multiple backfilling before the recovery of a secondary stope, resulting in a layered structure of backfill in stope. Therefore, it is significant to investigate the deformation responses and mechanical properties of stratified cemented tailings backfill (SCTB) with different layer structures to remain self-standing as an artificial pillar in the primary stope. The current work examined the effects of enhance layer position (1/3, 1/2, and 2/3) and thickness ratio (0, 0.1, 0.2, and 0.3) on the mechanical properties, deformation, energy evolution, microstructures, and failure modes of SCTB. The results demonstrate that the incorporation of an enhance layer significantly strengthens the deformation and strength of SCTB. Under a confining pressure of 50 kPa, the peak deviatoric stress rises from 525.6 to 560.3, 597.1, and 790.5 kPa as the thickness ratio of enhance layer is increased from 0 to 0.1, 0.2 and 0.3, representing a significant increase of 6.6%, 13.6% and 50.4%. As the confining pressure increases, the slopes of the curves in the elastic stage become steep, and the plastic phase is extended accordingly. Additionally, the incorporation of the enhance layer significantly improves the energy storage linit of SCTB specimen. As the thickness ratio of the enhance layer increases from 0 to 0.1, 0.2, and 0.3, the elastic energy rises from 0.54 to 0.67, 0.84, and 1.00 MJ·m⁻³, representing a significant increase of 24.1%, 55.6% and 85.2%. The internal friction angles and cohesions of the SCTB specimens are higher than those of the CTB specimens, however, the cohesion is more susceptible to enhance layer position and thickness ratio than the internal friction angle. The failure style of the SCTB specimen changes from shear failure to splitting bulging failure and shear bulging failure with the presence of an enhance layer. The crack propagation path is significantly blocked by the enhance layer. The findings are of great significance to the application and stability of the SCTB in subsequent stoping backfilling mines.

Keywords

stratified cemented tailings backfill / enhance layer / triaxial compressive tests / mechanical properties / energy evolution

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