| With the continuous development of infrastructure construction in China,the demand of artificial aggregate is increasing day by day.The production of artificial aggregate needs blasting fragmentation and mechanical crushing successively,so the study on the utilization and control of explosive energy during the whole process of exploitation and procession of artificial aggregate has a great significance on revealing the transmission and distribution mechanism of energy in rock blasting,optimizing the blasting design,improving the utilization efficiency of explosive energy,and reducing the whole energy consumption in the production of the artificial aggregate.This paper focuses on the scientific problem of the utilization and control of explosive energy in the production of artificial aggregate.A series of researches were carried out with theoretical analysis,numerical simulation and field experiments.The main contents and conclusions of the research are as follows:Based on the breaking process in rock blasting,the distribution mechanism and calculation method of the main energy components are discussed,including the seismic energy,fragmentation energy,kinetic energy and so on.The seismic energy usually propagates in the form of blasting vibration,which will induce the blasting damage of retained rock mass near the explosive source or the blasting damage of buildings(structures)in the far blasting area,the blasting vibration signal at the surface is the main data to measure the seismic energy.Fragmentation energy mainly leads to the formation and propagation of cracks in rock blasting,including macro fragmentation energy and micro fragmentation energy,the former is mainly used to form new free surface of rock fragments after blasting,while the latter is mainly used to form micro cracks hidden in the rock fragments or retained rock mass.The kinetic energy is always used to throw the rock fragments to form muck pile,which is also the main reason of the existence of flying rocks,high-speed camera with motion analysis is the main method to measure the kinetic energy.In addition,the energy components in rock blasting also includes expansion energy,shock wave,thermal and so on,the effect and harm of each energy component should be considered in blasting design to use the explosive energy better.According to the mechanism of rock breaking,the calculation method of macro fragmentation energy and micro fragmentation energy are modified.In the field test at Hangudi limestone mine,the specific surface area of large rock fragments(particle size >150mm)and small rock fragments(particle size < 150mm)were measured by threedimension laser scanning and image analysis technology,respectively,combined with the fragmentation size distribution,the macro fragmentation energy was measured.With SPH-FEM coupling algorithm,the blasting damage distribution was simulated,and the micro fragmentation energy of each blasting test was calculated based on the theory of damage energy consumption.The result shows that the macro fragmentation energy was about 4.7% ～ 5.7% of the explosive energy,the useful macro fragmentation energy for artificial aggregate production accounts for about 2.1% ～ 2.3% of the explosive energy,while the micro fragmentation energy accounts for about 21.4% ～24.7% of the explosive energy,which is 4～5 times of the macro fragmentation energy.The macro fragmentation energy only accounts a small part of the explosive energy,and most of it is consumed in the very fines(mass fraction < 2%).In engineering,the blasting scheme should be optimized to increase the macro fragmentation energy and improve its distribution.The influence of charge structures on the fragmentation energy is studied.The range of cracked zone and energy transmission efficiency of explosive in different charge structures are analyzed theoretically,with fluid-solid coupling algorithm,the influence of charge structures on the blasting effect was simulated.The result showed that though the energy transmission efficiency is higher in the coupled charging,the damage distribution is concentrated and the fragment size distribution is uneven,while the damage distribution is more uniform and the fragment size distribution is improved in the decoupled charging,which is also benefit to break the rock at orifice.Meanwhile,the water-decked blasting is more conductive to the transmission of explosive energy than air-decked blasting,and blasting damage level of rock between the blasthole is higher.Field tests were carried out to compare the fragmentation energy in different charge structures,it was found that the fragmentation size distribution was more uniform in air-decked blasting,and the proportion of macro fragmentation energy consumed in fines(2%< mass fraction < 20%)and centrals(20%< mass fraction < 80%)is higher,so the distribution of fragmentation energy is reasonable.Compared with the air-decked blasting,the ratio of macro fragmentation energy is higher in water-decked blasting,and the macro fragmentation energy consumed in the very fines(mass fraction< 2%)is more.The influence of hole pattern parameters on the fragmentation energy is studied.The fragment size distribution and macro fragmentation energy in different hole pattern parameters are analyzed theoretically,with SPH-FEM coupling algorithm,the influence of hole pattern parameters on the blasting effect was simulated.The results showed that the small coefficient of hole-spacing will lead to over breaking of rock mass between the blasthole,and the cracks between the blasthole will also interpenetrate in the early stage,but the rock inside the bench is not fully broken.Properly increasing the coefficient of hole-spacing can improve the fragment size distribution and the energy transmission efficiency,but too large of it will lead to the blasting roots between the blasthole,and the flying rocks at the surface of the bench.Field tests were carried out to compare the fragmentation energy in different hole pattern parameters,it was found that fragmentation energy did not show a positive correlation with the coefficient of hole-spacing as smaller space means more very fines,but the fragment size distribution is more uniform with greater coefficient of holespacing,and the ratio of fragmentation energy consumed by fines(2%< mass fraction< 20%)and centrals(20%< mass fraction < 80%)is higher,so the distribution of macro fragmentation energy is more reasonable.Considering limestone crushing process,the influence of blasting parameters on energy consumption of rock mechanical crushing is studied.From the utilization rate of limestone and the control of energy consumption,the formation mechanism and control methods of rock powder in rock blasting is analyzed in theory,as well as the main factors of coarse crushing energy consumption.Based on the screening test,the rock powder in blasting and energy consumption in coarse crushing with different blasting parameters are measured in the field test.The result showed that the crushed zone around the blasthole is the main source of rock powder,it can be well controlled by the air-decked blasting,mixed charging and other technologies,so the utilization efficiency of limestone can be improved.With the blasting parameters of large space and small burden,and properly increasing the powder factor,the crushing efficiency of machine can be improved and the breaking ratio can be decreased,so the energy consumption in coarse crushing can be reduced. |
