Triaxial mechanical behavior and damage evolution of stratified cemented tailings backfill incorporating an enhancement layer

Abstract

Primary stope frequently experience partial backfill collapses during subsequent stoping and backfilling operations due to insufficient strength of the primary stope. To enhance the stability and mechanical performance of the primary stope, an enhancement layer was introduced into the middle layer of the backfill. In this paper, the mechanical properties, energy evolution, and damage progression of cemented tailings backfill (CTB) and stratified cemented tailings backfill (SCTB) were systematically investigated through triaxial compression tests on specimens cured for 3, 7, and 28 days. The results indicate that the stress-strain response of SCTB exhibit four distinct stages, interlayer voids and pore closure, rapid increase of stress, slow increase of stress, and stress decline, with elastoplastic deformation becoming more pronounced under higher confining pressures. The SCTB specimens cured for 3 days exhibit inferior mechanical properties compared with CTB specimens of the same age; however, when the curing age extended to 7 and 28 days, SCTB demonstrates superior strength and deformation characteristics. The failure modes of SCTB transitions from conjugate shear and tensile failure to a bulging and shear hybrid failure, whereas CTB primarily undergoes uniform shear failure, indicating that the enhancement layer effectively suppresses crack propagation. The energy storage limit of SCTB cured for 7 days is 13.5% higher than that of CTB, increasing to 61.1% at 28 days. The SCTB exhibit a delayed onset of accelerated damage compared with CTB. These findings provide valuable guidance for designing cost-effective, high-performance backfill systems in mining engineering while balancing structural strength and sustainability.