Delay Time Optimization Of Ore-Rock Separation Blasting In Open-Pit Mining Of Yunshan Graphite Mine

In the process of open-pit mining,ore loss and dilution exist for a long time along with the mining process,and are related to many factors.The main reason is that there are multiple ore-rock interfaces between ore and rock due to the complex occurrence conditions of ore body.The existence of ore-rock interfaces leads to the mixing of ore and surrounding rock blasting pile after blasting operation,and there is no obvious boundary between the blasting pile,resulting in the mixed loading of ore and rock in shovel loading work,which directly improves the loss rate and dilution rate of ore.Therefore,it is of great significance to carry out relevant research on the blasting problem in the mixed blasting zone of open-pit mine,for reducing the loss rate and dilution rate in the mining process of open-pit mine,and improving the production efficiency and resource utilization rate.Based on the national key research and development program project and the open-pit graphite mine where the project was tested,the action principle of ore-rock separation blasting technology was analyzed based on millisecond delay blasting technology,and the theoretical formula to determine the delay time was summarized.SHPB impact tests of graphite ores with different grades and surrounding rock were carried out to obtain the characteristics of crushing energy consumption of graphite ores with different grades and surrounding rock.The SPH-FEM coupling algorithm of two-hole millisecond rock blasting was simulated by ANSYS/LS-DYNA software,and the throwing law of rock media with different delay time was obtained.The numerical simulation of delay time optimization of ore-rock separation blasting was carried out to obtain the optimized delay time and realize the ore-rock separation effect under blasting action.The main results are as follows:(1)In the graphite ore and wall rock specimen SHPB impact compression test,the same strain rate under the condition of surrounding rock dynamic compressive strength,the utilization rate of energy and fracture energy density are bigger than graphite ore,and surrounding rock crushing grain size is the same energy density under the condition of three grade graphite ore crushing grain size is larger,and the higher the grade,graphite ore crushing particle size smaller.(2)In the numerical simulation experiment of rock-ore separation blasting,both the peak velocity and the stable throwing velocity of rock-ore medium increase first and then decrease with the increase of delay time,and the peak velocity of each node reaches the maximum value at 15 ms,and the stable throwing velocity of the node in the ore area reaches the maximum value when the delay time is 10 ms.When the delay time is 15 ms,the steady throwing velocity reaches the maximum value When the delay time of the borehole at the boundary is 60 ms,the funnel of the first blasting borehole is basically formed.(3)In the numerical simulation test of ore-rock separation blasting with different delay time between rows,the peak velocity of the node at the hole where the rear hole is first detonated reaches the maximum value when the delay time is 40 ms,and the peak velocity of the node at the hole where the subsequent detonation occurs reaches the maximum value at about 40 ms.In conclusion,the graphite flake has a weakening effect on graphite ore.The optimized delay time of ore and rock separation is 15 ms between holes,60 ms delayed at separation boundary and 40 ms between rows,which can realize ore and rock separation.