Study On Effect Evaluation Of Blast With Existing Goaf And Optimization Of It’s Blasting Parameters

Flat back east open-pit coal mine in Shanxi, due to the goaf existing under surface, Bench blasting technology need to be further improved to overcome the existing problems. These questions including the blasting vibration on taconite roof stability of soil slopes,block rate,back cracks,hole punching and the selection of explosive specific charge, etc.For the problems existing in the bench blasting,using the fuzzy analytic hierarchy process(ahp), setting up blasting effect evaluation model,the blasting effect can be evaluated;By using ANSYS to simulate the blasting vibration effect on roof stability of mined-out area;Based on roof stability of mined-out area,by means of ls-dyna simulation and field test, the bench blasting parameters were optimized.Based on the actual situation of mined-out area existing in East open-pit,getting the following conclusions:(1) Based on East open-pit field condition that existing the underground mined-out area,selecting the 3 level evaluation index and 10 secondary, then set up hierarchy structure of at all levels indexes,based on hierarchical structure,applied in determining weights of indicators at all levels and membership function,and finally establish East open-pit bench blasting effect evaluation model. calculating a comprehensive analysis and evaluation of blasting effect.According to the evaluation results of East open-pit blasting effect,bench blasting technology is still existing optimizing space; the safe distance between bench blasting and mined-out area is 200 meters; Minimum safe thickness of roof is 35 meters.(2)On the basis of evaluation,by using East open-pit’s blasting design software and existing equipment, designing scheme of 12 groups of blasting parameters,the blasting parameters are simulated by using ls-dyna,by analysis contrast various indicators of the simulation results under different blasting parameters.The result of ls-dyna to simulate hole best net parameter is 7 x 6,using rectangular holes arrangement.(3)According to the simulation results of ls-dyna,it is concluded that the mined-out area is suitable for the east open-pit existence hole bench blasting a hole arrangement and network parameters,after verified by field test. compared with field test of blasting effect,the result is consistent,finally draw a rectangle holes arrangement.Through the field test results,verify the correctness of the simulation results.The research results show that the existence of mined-out area East open-pit blasting effect still existing some problems,the steps of the optimized blasting parameters have improved the blasting effect, the roof goaf stability have solved at the same time,achieve the expected goal.