Technology Reasearch And Application Of Deep Presplit Blasting In Hard Roof

The hard roof of mechanized mining face collapse brings the suddenimpact on the brackets and people, so it s a serious threat to the production ofcoal mine safety.Relying on Yangquan Coal Co. Guoyang mine K8205fullymechanized caving face, based on the existing explosion fracture and damagetheory, the theoretical study of the hard roof deep hole pre-split blastingcracking mechanism and hard roof fracture mechanism are focused on.Underthe detonation stress waves and gas,the extension length of the crack and thefirst and periodic caving span are explored. Through numerical simulationmethods, borehole wall pressure changes among the v-groove blasting fracturemodel, cutting seam cartridge blasting fracture model and decouple chargeblasting model are compared.Cutting seam cartridge non-coupling coefficientand the width of slit are simulated to verify the veracity of the hole spacing.Finally, through the analysis to the monitoring data from the site,reasonability of the blasting design is verified. The main contents andconclusions are as follows.(1)This paper clearly illustrates the hard roof deep hole pre-split blastingcracking mechanism. Blasting crack formation mechanism is explained throughthe interaction between the detonation stress waves and gas and exposes the essence of the question.(2)Through the mechanical model analysis of the hard roof rock beam, thecomputational formula of the first and periodic caving span is obtained.(3)According to the actual situation to choose the modeling parameters,v-groove blasting fracture model, cutting seam cartridge blasting fracture modeland decouple charge blasting model are respectively established. Comparing theborehole wall pressure of three different models, it is found that the blastingeffect of cutting seam cartridge blasting is better than v-groove blasting.Through the simulating of cutting seam cartridge non-coupling coefficient andthe width of slit, it is obtained that when the thickness of PVC pipe and otherparameters are determined, take the radial non-coupling coefficient2.81and thewidth of slit6mm,using cutting seam cartridge is the best.(4)Take the blast hole diameter90mm, non-coupling coefficient1.5andhole spacing5.5mm, the simulation analysis of double hole blasting model isdone. According to the different moments of stress nephogram and thestress-time curve of all measuring points, it is obtained that in the middle of thetwo hole of2.75m, the maximum tensile stress is greater than the tensilestrength of the roof rock.This shows that the two blast holes are completelyversed, the fissure is completed developed to demonstrate the rationality of theblast hole spacing.(5)According to the actual situation, reasonable blasting parameters andassociated safety precautions are determined and blasting caving effect according to the changes of the mining hydraulic support resistance is analyzed.