Mix ratio optimization of alpine mine backfill based on the response surface method

Central composite design (COD) experiments were performed to investigate the effect of stope temper-ature, cement-to-tailings mass ratio and the mass fraction of solid phases in the backfill slurry on the backfill strength characteristics and slurry flow properties for an alpine mine. Response surface regression models of backfill strength, slurry slump and the cost of filling materials were established by the substitution of a polynomial for the implicit limit state equation. Taking the desirability of the above regression models as inputs, the overall desirability of the back-fill slurry's performance was calculated by a weighted geometric average algorithm. The filling mix parameters were optimized by the method of nonlinear multi-objective based on the overall desirability criteria, and the optimal cement-to-railings mass ratio and slurry transportation concentration were obtained for the alpine mine in different temperature situations. It is found that at the stope temperature less than 5℃, the overall desirability of the backfill slurry is in the range from 0.4 to 0.5 when the mass fraction of solid phases in the backfill slurry is 70% and the cement-to-tailings mass ratio is 1:6. Under that condition, the backfill slurry meets the challenge of low temperature and the overall desirability primary keeps invariable with the change in temperature. But at the stope temperature higher than 5℃, the overall desirability improves significantly with the temperature increasing, and it raises fastest when the mass fraction of solid phases in the backfill slurry is 65% and the cement-to-tailings mass ratio is 1:6.