Numerical Simulation And Optimization Of The Relationship Between Hole Spacing And Aperture Multiple In Presplitting Blasting

In the pre-splitting blasting work,whether a smooth slope is formed is an important index to evaluate the blasting effect,and the quality of the pre-cracking directly affects the smoothness of the slope.The formation of pre-cracks is mainly due to the combined effect of blasting stress and blasting gas.If it is greater than the ultimate tensile strength of the rock,pre-cracks are formed.Designed reasonable blast hole diameter and blast hole spacing are the most important links in pre-split blasting.The empirical formula for blast hole spacing commonly used in engineering a=(7-12)d may affect the blasting effect due to geological conditions,artificial errors and other conditions if the blast hole spacing is too small,it may cause excessive damage to the rock and affect the flatness of the slope.If the blast hole spacing is too large,the rock may not form pre-cracks,which will not meet the engineering requirements.Through the study and research on the mechanism of pre-splitting blasting and rock breaking,the conditions of pre-cracking are analyzed.For open pit mines,the rock and explosive parameters have a certain influence on the blasting effect,and reasonable hole network parameters are the important factors that determine the blasting effect.By collecting open-pit data,using PRO/E Wildfire5.0 modeling and using Hypermesh14.0 LS-DYNA module,it is established that the commonly used apertures in engineering are 90 mm,100mm,110 mm,120mm,130 mm under the condition that other parameters remain unchanged.,30 sets of calculation models with 7-12 times the relationship between the hole distance and the multiple of the hole diameter;at the same time,the calculation models for the delay of 1ms and 5ms are also calculated.By comparing whether the tensile stress generated by the blasting at the midpoint of the blasthole line is greater than the ultimate tensile strength of the rock,the basic criterion of rock formation is determined,and the best blasthole spacing under different apertures is obtained.The simulation results obtained are sorted and analyzed,and fitted by ORIGIN 2018.Under the condition that other hole network parameters remain unchanged,the change curve k=0.059d+3.18 of the multiple relationship between the blasthole spacing and the aperture(90mm-130mm).When simulating the delay error,it is found that the error within 1ms will basically not affect the blasting effect,but when the delay is 5ms,the effective stress drops,the stress superimposition area shifts,and the first seam position may also shift.In engineering practice,the pre-split blast hole group blast hole can be used to reduce the harmful effects of blasting.According to the on-site construction analysis of the pre-splitting blasting work of the Haiming Open-pit Mine,the hole network parameters were designed using the formula obtained by the simulation calculation,and a good blasting effect was obtained.The feasibility of the computer simulation results can be known through verification.Blasting engineering has a certain degree of guidance.