Ultra-fine tailings have become the main source of filling materials. In order to facilitate mixture ratio design and strength prediction of filling slurry

based on the microstructure of ultra-fine slurry

solid filling rate is used to characterize the structure of filling slurry. 63 sets of proportioning strength tests are carried out on ultrafine tailings of a mine. The results show that the solid filling rate and water cement ratio have exponential and negative power functions relation with the unconfined strength of the filling body respectively. The correlation between the solid filling rate and the water cement ratio is obtained by using the Pearson theory. It is found that the solid filling rate and the water cement ratio are independent of one another. Then on this basis

a double variable strength calculation model of ultra-fine tailings cemented hydraulic fill is developed. The error between the calculated value and the experimental value is less than 7%. Besides

experiments on the strength of ultra-fine tailings cemented body with curing time are carried out. A mathematical model of strength-age and a formula for calculating the strength of three variables are established using the fitting law of the experimental data. The developed model not only predicts the strength of mine filling body accurately

but also guides the preparation of mine filling slurry effectively.