Numerical Simulation And Determination Of Reasonable Blasting Hole Deep In Deep-hole Step Blasting In Open Pit

On the open bench blasting,bedrock is an important indicator for evaluating the effectiveness of blasting.The main reason of existing bedrock is that acting force is overlarge at the bottom of the hole and blasting wave is too weak.The rock on the bottom line of bench cannot be broken.The purpose of sub-drilling is that to overcome the acting force of chassis and to solve effectively the problem of bedrock.However,in the actual operation of open bench blasting,the value of sub-drilling depend on experience.If the value of sub-drilling is little,sub-drilling will not break the rock on the bottom line of bench.If the value of sub-drilling is bigger,the rock on the bottom line of bench will be smash.Excessive vibration will cause huge influence of the drilling of the next step.The super of sub-drilling will cause explosive waste and enhance the actual production cost of mine.Through studying the mechanism of rock fragmentation,step rock fragmentation and the mechanism of ultra-deep blasting hole,the influencing factors of ultra-deep blasting are analyzed.For open-pit mines,the explosivity of explosives and rocks has a certain impact on the ultra-deep,and the hole network parameters have a very important impact on the ultra-deep,which is affected by the chassis resistance line and hole diameter,and their size directly affects the value of the ultra-deep.Through collecting and sorting out data in mines,128 calculation models of chassis resistance lines of 525 cm,550 cm,575 cm and 600 m,aperture of 100 mm,150 mm,170 mm,200 mm,ultra-depth of 0 cm,25 cm,50 cm,62.5 cm,75 cm,87.5 cm,100 cm and 125 cm were established by using PROENGINEER Wildfire and HyperMesh 14.0 under certain other hole network parameters.LS-DYNA is used for post-processing.By comparing the maximum effective stress of the continuous element selected at the bottom of the step slope with the yield strength of the rock,the criterion for judging whether the rock is broken or not is obtained.The optimum ultra-deep value under different chassis resistance lines and pore diameters is obtained.By collating and analyzing the simulated data,certain conditions of other pore network parameters are obtained by MATLAB fitting.Under this condition,the relationship between ultra-deep and chassis resistance line and aperture h =-0.436 × d + 0.575 × w-180.80.The deep hole bench blasting for rock peeling in No.6 coal seam of Shaerhu Open-pit Coal Mine is tested and analyzed in situ.The blasting schemes under different conditions will be selected selectively according to the peeling rock in the main mining area.Comparing the blasting effects of different super-depth under different chassis resistance lines and apertures,it is proved that the results of computer simulation are basically authentic,reliable and the data fitting from computer simulation is feasible to obtain the relationship between super-depth and chassis resistance lines and apertures.