| During drilling and blasting in open pit mines in high and cold plateau areas,water gushing or freezing often occurs inside the blast hole after charging,and the blasting effect and mechanism of the charge will change under different coupling medium environments.In this case,it is obviously unreasonable to determine blasting parameters based on conventional design methods without considering the effect of coupling medium.Therefore,based on the theoretical models such as explosion dynamics theory,stress wave propagation theory,and rock mass blasting fragmentation,this paper systematically studies the distribution of rock breaking energy during borehole blasting in different coupling media in high and cold regions of the plateau by combining theoretical analysis,on-site blasting funnel test,and ANSYS/LS-DYNA finite element simulation software analysis,taking the Jiama Open Pit Mine in Mozhugongka County,Lhasa City as the supporting object,At the same time,the optimized blasting parameters for the project are proposed,and the research results are applied to the on-site actual blasting.Finally,the blasting effect is evaluated based on the Split Desktop 64 fragmentation statistical system.The specific research content and results are as follows:(1)Through theoretical analysis,a formula for the initial pressure on the hole wall consistent with the properties of explosives is derived.It is found that both the hole wall pressure and the quasi static pressure decrease with the increase of the uncoupling coefficient,and under the same coupling coefficient,the initial pressure and the quasi static pressure values on the hole wall of water media uncoupled charge blasting are higher,with the peak value of the initial pressure on the hole wall being times that of air media,The decay speed of the initial pressure value and the quasi static pressure value is significantly lower than that of the air uncoupled charge.(2)In the 48 blasting funnel tests of uncoupled charge blasting in air,water,and ice media,the energy utilization of uncoupled charge blasting in water media is relatively better,followed by uncoupled charge blasting in ice media,and the energy utilization rate of uncoupled charge blasting in air is the lowest.When the decoupling coefficient is 1.2,the volume of the water and ice media crushing funnel increases by 21.66% and 20.02% on average,and the average unit consumption decreases by 17.80% and 16.68% compared to the volume of the air decoupling charge blasting funnel;When the decoupling coefficient is 1.33,the visible funnel volume of water and ice media increases by 32.09% and 26.55% on average compared to that of air decoupling charge blasting,and the average unit consumption decreases by 24.29% and 20.98%;When the decoupling coefficient is 1.50,the visible funnel volume of water and ice media increases by 19.73% and15.52% on average,and the average unit consumption decreases by 16.48% and 13.44% compared to that of air decoupling charge blasting;When the decoupling coefficient is 1.71,the visible funnel volume of water and ice media increases by 16.91% and 8.73% on average compared to that of air decoupling charge blasting,and the average unit consumption decreases by 14.47% and 8.03%.(3)According to the field test and monitoring results,compared to air uncoupled charge blasting,the peak vibration velocity of water uncoupled charge blasting can be reduced by 25.33%,while the peak vibration velocity of ice uncoupled charge blasting can be reduced by 11.24%.The unit consumption of rock breaking using water or ice as the coupling medium can be reduced by about 18.9% compared to the amount of air uncoupled charge.(4)Based on the simulation results of ANSYS/LS-DYNA,it can be concluded that after the same blasting time,the radius of the funnel crushing zone of water medium uncoupled charge blasting can be increased by 1.04 to 1.11 times compared to that of air medium uncoupled charge blasting,and the radius of the fracture zone can be increased by 1.48 to 1.19 times;The radius of the funnel crushing zone in ice media with uncoupled charges can be increased by 1.02 to 1.12 times compared to that in air media with uncoupled charges,and the radius of the fracture zone can be increased by 1.48 to 1.15 times.The increase in the radius of the crushing zone caused by uncoupled charging blasting in water and ice media is not significant,but the range of the fracture zone is significantly increased.(5)Explosives of the same mass consume the largest amount of energy in air media.Among them,when the coupling medium is water,the kinetic energy generated by the rock mass increases by 33.33% compared to when the coupling medium is air,and the total energy absorbed by the rock mass increases by 46.03%.When the coupling medium is ice,the kinetic energy generated by the rock mass increases by 28.21% compared to when the coupling medium is air,and the total energy absorbed by the rock mass increases by 35.15%.Considering the efficiency and convenience of on-site construction,the uncoupled charging of water and ice media can be uniformly reduced to about 20% of the explosive mass.(6)Applying the research results to the field practice,the optimized blasting scheme reduces the boulder rate from 8.9% to 4.3%,and the original blasting scheme has a unit consumption of0.44 kg/m3.The unit consumption in water and ice blast holes after reducing the charge is 0.36kg/m3,which can reduce the unit consumption by 18.2%,significantly improving economic benefits.The research results can provide reference for similar projects.The paper has 70 diagrams,23 tables,and 92 references. |
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