| Blasting technology is widely used in open pit mining.With the continuous expansion of open pit mining scale,more requirements are put forward for blasting mining technology.When blasting broken rock mass is used,the size（lumpiness）,foundation and blasting vibration intensity of the broken rock mass after blasting are important indexes to evaluate the blasting effect.However,different mines have great differences in rock properties,mining conditions and surrounding environment,so it is necessary to adjust and optimize the blasting parameters according to the actual conditions,so as to achieve the expected blasting effect.Based on the basic theory of rock blasting,taking Changshenshan Limestone open-pit building material mine in Chizhou City as the engineering background,the physical properties,uniaxial compressive strength,tensile strength and dynamic compressive strength of typical limestone were obtained through on-site rock sampling,processing and testing.Using ANSYS/LS-DYNA finite element numerical simulation software,the numerical calculation model of deep hole step blasting was established,and the characteristics of rock explosive stress field under different hole layout parameters and charging structure were obtained.The field test blasting parameters were proposed and verified.The main conclusions of the study are as follows:（1）The limestone samples obtained from the Changshen Mountain site in Chizhou City are cored,cut and polished into standard rock test samples.The results show that the compressive strength of the mine limestone is 62.31MPa,the tensile strength is 5.5MPa,the Poisoned son ratio is 0.25,the density is 2795.66 kg·m-3;It provides the basis for theoretical analysis and numerical calculation.（2）Establish a three-dimensional model of step blasting in open-pit mines,and study the influence of hole plugging length,super depth and hole spacing on step blasting effect.The hole plugging length of 4 m has the best damage effect on rock compared with the monitoring points of 2 m and 3 m with the maximum effective stress value.The maximum effective stress of each monitoring point at the super depth of 2.5 m has better damage effect on the rock than that at the super depth of 2 m and 3 m.When the hole spacing is6.5 m,the maximum effective stress value of the middle point of the hole line is the best.Finally,it is determined that the best blasting effect can be achieved when the hole plugging length is 4 m,the super depth is 2.5 m and the hole spacing is 6.5 m.（3）Field tests are carried out according to optimized parameters related to step blasting.The software Wip Frag is used to analyze the degree of rock after blasting,and the results show that the size of rock generated by blasting is less than 100 cm and more than 90%,and the proportion of broken rock larger than 100 cm is only 1.9%.The large block rate generated by blasting is low,and the expected blasting effect is achieved.At the same time,the blasting vibration detector installed in the blasting area shows that the vibration generated by blasting meets the design requirements,and the blasting effect produced by the optimized blasting parameters is good.Figure[55]Table[27]Parameter[70]... |
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