| The non-pillar sublevel caving method has become one of the main mining methods used in underground metal mines in China due to its unique advantages.The poor blasting effect is a common problem with this method in production practice.The root cause of this is that the mine's hole network parameters,charge structure,detonation form and construction techniques do not match the lithology of the ore body well.The blasting effect in the pilot mine of the bottomless pillar section collapse method in the second west mining area of a mine was not very satisfactory during production,which seriously affected the recovery index and production efficiency of the mine.In order to improve the overall blasting effect of the mine and increase the production efficiency of the mine,the following research has been done in this paper.Firstly,through on-site research,it was found that the blasting of the first section of the test quarry had problems such as serious polarisation of the block size of the crumbling ore,damage to the brow line of the back row of holes and blocking of individual holes in the back row of holes,and further analysis of the impact of blasting problems on normal mine production based on the current state of blasting.The results of the analysis show that poor blasting results can increase the depletion rate of the mine,increase the loss of ore and increase mining costs.Secondly,the first mining section blasting problem is analysed by combining theoretical and numerical simulations with the rock-breaking mechanism of the fan-shaped shell hole.The results of the analysis show that the mine's blasting method,blockage length and some of the hole network parameters are unreasonable and are the main causes of the mine's blasting effect.Then,based on the results of the previous analysis and the fact that the first section of the mine had already been laid out,the blasting solution was proposed to adjust the detonation method to bottom section detonation and optimise the blockage length,and the blasting effect after the adjustment was analysed using numerical simulation.Based on the simulation results,a comparison of the stress distribution,crack generation and effective stress magnitude of typical cells before,after blasting method adjustment and optimisation shows that blasting results are better with bottom of hole segmentation and optimised blocking length.The results of the field blasting tests show that the use of bottom section blasting and optimisation of the blockage length significantly reduces the number of large blocks,the crumbling blast pile is dominated by small and medium-sized ore,with a larger proportion of fines,the probability of brow line damage and blockage of the wrong hole in the back row of holes is reduced,and the overall blasting effect of the first mining section of the test quarry is significantly improved.Finally,in conjunction with the results of the study on improving the blasting effect in the first mining section of the test quarry,a 9-hole layout was proposed for the next section of the first mining section,and numerical simulations were used to verify the feasibility of the 9-hole layout.The results of the simulations show that the 9-hole arrangement produces more uniform cracks and the effective stress magnitude of the typical unit is closer to the theoretical calculation.Based on the numerical simulations,it can be assumed that the 9-hole arrangement not only ensures effective ore fragmentation,but may also provide better blasting results.In summary,the blasting solution proposed in this paper,using bottom of hole segmentation and optimising the blockage length,can effectively improve the overall blasting effect of the first mining segment of the test quarry,and the 9-hole layout proposed in this paper has some reference value for the design of blasting parameters for the next segment of the first mining segment of the test quarry.The methodology and results of this paper can be used as a reference for mines with similar blasting problems. |
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