Abstract: In view of the poor gradation of waste stone bar grit blended coarse aggregate in Jinchuan Mine， the problem of segregation of filling slurry is solved. Limestone aggregate is added to improve aggregate gradation and improve filling effect. Firstly， the physical and chemical analysis of the aggregate is carried out， and on this basis， the particle size distribution analysis of the mixed aggregate is carried out. Secondly， the strength test of the mixed aggregate filled with limestone powder and the pipe transportation characteristics of the slurry are carried out. Then， based on the test results， the BP neural network model is established to predict the strength of the filling body and the pipe transportation characteristics of the slurry，and the mix proportion of the mixed aggregate filling slurry is optimized. The study results show that: adding appropriate amount of limestone powder can not only effectively improve the particle size distribution and strength of the filling body， but also improve the fluidity of the filling slurry， which is beneficial to the pipeline transportation characteristics of the filling slurry， and can significantly improve the filling effect.The optimal proportion of the filling slurry is as follows: the amount of cementitious material is 310 kg/m3， the content of limestone powder is 12.3%， and the mass concentration of slurry is 80%.It has been verified by sampling during industrial filling that The slump， consistency， bleeding rate， 3 d， 7 d and 28 d compressive strength are 25.41 cm， 9.31 cm， 6.7%， 2.7 MPa， 5.1 MPa and 10.6 MPa respectively， which can meet the requirements of mine industrial filling， and the cost of unit filling is reduced by 21%.

Key words: filling mining, limestone powder, mixed aggregate, proportion, strength, pipeline transportation characteristics, optimization