Creep characteristics and nonlinear creep model of loess-slag-based cemented backfill: Considering the effects of curing time and confining pressure

To address the high carbon footprint of traditional backfills and the lack of long-term stability data for highwall backfill mining, a low-carbon loess-slag-based cemented backfill (LSCB) was developed. This study investigates the time-dependent mechanical behavior of LSCB through triaxial creep tests under varying curing times ( t c ) and confining pressures ( σ 3 ), supplemented by microstructural characterization. Results indicate that instantaneous strain increases linearly with stress, with the slope decreasing as t c extends but remaining insensitive to σ 3 . Creep strain exhibits nonlinear growth above a critical stress threshold that rises with both t c and σ 3 . Both long-term and creep failure strengths increase nonlinearly with t c and σ 3 , while their ratios to peak strength remain stable. Extending t c promotes geopolymer gel formation to densify the internal structure, and increasing σ 3 constrains crack initiation and propagation. To predict the creep behavior of LSCB, a nonlinear visco-elasto-plastic creep model was established and extended to three dimensions using tensor decomposition and the Drucker-Prager criterion. The proposed model outperforms classical models in capturing all creep stages, particularly the accelerated failure phase. This work establishes a theoretical basis for the stability design of green backfill, advancing solid waste utilization in sustainable mining. • A new low-carbon backfill material - loess-slag-based cemented backfill (LSCB). • The influence of curing time and confining pressure on the creep behavior of LSCB. • Prediction of long-term strength and creep failure strength of LSCB under varying curing time and confining pressure. • Construction and three-dimensional extension of the nonlinear viscoelastic-plastic creep model of LSCB. • Theoretical support for the long-term stability of highwall backfill mining in open-pit coal mines.