Experimental Study On Pre-mixing Of Barren Rock In Face-end Ore-drawing Of High Section Non-pillar Sublevel Caving

Aiming at the pre-mixing of barren rock problem of high section non-pillar sublevel caving method ore drawing process in an iron ore,in this paper,comprehensive research methods were adopted,which are field tracking ore drawing investigation,Analysis of ore drawing theory,laboratory physical experiment and numerical simulation experiment.This paper has strong strong engineering practicability,and the main results are as follows:(1)Through processing and analyzing the experimental data of track ore drawing in the field and combining with the theory of ellipsoid ore drawing,it is preliminarily determined that the mismatching between the current ore drawing step and the movement law of ore and rock,the blasting pushing wall and the large block output are the main reasons for the early mixing of waste rock.In addition,by comparing the recovery rate of ore under three factors,the influence of mismatching of ore step distance and movement law on the advance mixing of waste rock is more significant than that of wall and block.(2)Based on the study of ore fluidity by physical ore drawing experiments in the laboratory,the approach distance and the step distance matching with the movement law of ore and rock are calculated with the MATLAB and the theory of ellipsoid ore drawing.The comparative analysis with engineering practice shows that the main reason of the pre-mixing of barren rock is too small ore actual collapse step.(3)Based on the orthogonal experiment of L9(3~4),the natural resting Angle of ore rock was fitted to obtain the meso physical parameters of ore rock.The numerical simulation study of stope structure parameter optimization was carried out by using PFC3D software.combined with the field tracking survey of ore drawing and the movement law of ore rock,the stope structure optimization parameters(sectional height×approach spacing×collapse step)were obtained by establishing PFC3D numerical drawing model,which are 20m×15m×3.8m.(4)The parameters of fan-shaped medium and deep hole blasting are designed to improve the current blasting effect and match the optimized stope structure parameters.Blasting parameters are as follows:9?10 holes are arranged in each row,the aperture is 74mm—80mm,the hole bottom distance is 2.4-2.8m,the minimum resistance line is 2m,and the side hole Angle is 50°and 55°.The blasting method is differential blasting with non-electric initiation at the hole bottom,two rows at a time and three stages.