Theoretical And Experimental Research On Vertical Undercut For Large Diameter Holes

The vertical deep hole cutting blasting of roadway excavation is widely μsed in mine production activities.Due to the high requirements for blasting conditions,the excavation blasting is greatly affected by the clamping effect of surrounding rock,and there is only one free surface,so the hole utilization rate is low and the circulating footage is small.In order to solve the above problems,based on the practical excavation problems in the middle and western section of No.285 mine of Dahongshan Copper Mine,two kinds of vertical deep hole cutting blasting methods including large diameter hollow hole cylindrical cutting and large diameter hollow hole symmetrical cylindrical cutting were selected by μsing the relevant theoretical knowledge of blasting dynamics,rock mechanics,similarity theory and model test Through theoretical derivation and analysis,calculation of basic formula,model test of cut blasting and field application test,the mechanism of large diameter hollow hole vertical cut blasting is studied and analyzed,and the calculation formula of main blasting parameters is deduced.According to the statistical analysis of the final blasting results of model test,the influence of the change of cut blasting parameters on the vertical deep hole in roadway excavation can be further understood Based on the calculation of theoretical formula and the numerical analysis method of orthogonal design,the cavity formation mode and rock fragment throwing velocity distribution model of cut blasting are constructed.Based on the derivation of similarity theory,the model test of cut blasting in roadway excavation is carried out.The effects of hole layout,hole spacing,number of holes and charging sequence of holes on cut blasting are studied Finally,through the field test,the cutting blasting parameters are further optimized,and finally the optimal cutting blasting parameters of hard rock roadway are determined,and the test is successful in the 285 middle section and west section of Dahongshan copper mine.