| Bunch-holes blasting is a unique blasting form initiated by several dense parallel holes at the same time.It is mainly used in large-diameter deep hole mining in underground mines.There are some scientific problems in the study of bundle hole blasting,such as the transformation of blasting cavity shape and quasi-static rock fragment mechanism,the superposition of stress wave and reflection tensile rock breaking mechanism,the law of bunch-holes blasting crater and the realization of large-scale mining technology with bunch-holes.The study has important theoretical and practical significance.Based on the rock fragment theory of the combined action of explosion shock stress and detonation gas,the research is carried out according to the technical route of the basic law of bunch-holes blasting-blasting crater model-combined blasting crater model by using the methods of explosion mechanics,numerical simulation,blasting damage test and crater blasting test.Firstly,the basic law of bunch-holes blasting is studied.The comparative study of equivalent large hole(ELH)blasting and bunch-holes blasting with different hole spacing is carried out,and their blasting stress wave type characteristics,stress wave attenuation law and rock damage law are obtained.The concept of bunch-holes effect to enhance blasting action is put forward,and the mechanism of bunch-holes to enhance blasting is revealed:the energy of rock over crushing is less;The effective action time of blasting stress wave is longer,and the pressure in the blasting far zone is higher;The stress wave can enhance the crack propagation and the reflection tensile failure on the free surface;Enhanced rock fragment between bunches;It can connect and expand the capacity and enhance the quasi-static rock breaking of explosive gas;The restraint effect on blasting is enhanced,and the time of blasting gas acting on rock fragment is more sufficient.It is proposed that the reasonable holes spacing is the prerequisite for the effect of bunch-holes blasting.The effects of holes spacing on the volume of blasting crater and blasting damage are analyzed,and the optimal holes spacing is determined.Secondly,through blasting crater test,numerical simulation and theoretical analysis,the influence law of charge embedding depth on blasting rock fragment is studied.The Gaussian fitting model of blasting crater is established,and the physical and mechanical significance of model parameters is analyzed;A quantitative evaluation method for the influence of charge shape is proposed.The blasting efficiency function of equivalent blasting action of column charge is constructed,and the reasonable length-diameter ratio of equivalent spherical charge is determined;In order to reveal the characteristics of blasting stress,the law of rock damage and the formation mechanism of blasting crater,the research on blasting crater law of bunch-holes and equivalent large hole under different buried depth was carried out;The best charge buried depth of the bunchholes is determined.Thirdly,in order to realize high layered ore falling by blasting,the combined blasting crater of bunch-holes is studied.Based on the experiment and theoretical analysis of combined blasting crater with bundle-holes,the blasting model of short column bunchholes charge with choking gas relief and rock spallation by explosion gas was established,and the parameters of bunch-holes spacing were optimized.Finally,according to the enhanced fragment model of bunch-holes blasting,the open stope continuous caving mining method with bunch-holes blasting is developed.The optimized blasting parameters are applied to large-scale mining practice to realize crater blasting with bunch-holes column charge,break through the technical limitation that ordinary explosives can not carry out spherical charge blasting,and achieve remarkable technical and economic results. |
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