Assessment of cemented waste rock backfill for recycling gangue and controlling strata: creep experiments and models

Filling mining with cemented waste rock backfill (CWRB) is an optimal approach to eliminate the gangue waste pollution. To efficiently evaluate the gangue recycling and its advantage in structure protection, the effects of the confining pressure, cement dosage, and aggregate particle size distribution (PSD) on the creep behavior of CWRB were investigated. Burgers creep model was used to characterize the visco-elastic characteristics of CWRB, a visco-elastic-plastic creep model was established to describe its creep behavior on this basis. A genetic algorithm (GA) for optimizing the model parameters was constructed to verify the creep model. The time-varying evolutions of strata movements were discussed to evaluate the effect of the creep behavior of CWRB on the structural safeties. The results show that the creep load levels and times are positively correlated with the confining pressure and cement dosage, indicating that the consideration of roof load without confining pressure of surrounding rock causes an increase in the design parameters of CWRB to waste the cementing material. The creep load levels and times firstly increase and then decrease with the Talbot gradation index, revealing that CWRB with superior aggregate PSD performs the strong anti-deformation capacity under creep condition. The confining pressure, cement dosage, and aggregate PSD are comprehensively considered to optimize CWRB, and its stability under creep condition causes the strata movement to gradually slow down, thereby protecting underground aquifers and surface buildings.