Study On Test And Numerical Simulation About Air Interval Charge Blasting Under Cave Occurrence Conditions

Because of the occurrence of the cave,the blasting effects of the blasting in limestone open pit mine were worse.In order to improve the quality of the blasting in limestone open pit mine and guarantee the safety of blasting works,blasting test and numerical simulation were used to study the blasting of concrete models with different charge structure.The concrete models used were under three cave occurrence conditions.Then the air interval charge structure which could make the blasting effect best was analyzed and it could offer support for optimization of charge structure in blasting of limestone open pit mines which had cave occurrence.The research status of air interval charge technique and the blasting in open pit mines which had cave occurrence at home and abroad were fully studied.The rock broken process after explosives and the mechanism of blasting using air interval charge were deeply investigated.Based on the above works,the ollowing several studies were carried out.First,the concrete models were made and the caves were located at the bottom of the blastholes.After making the concrete models,the blasting tests were carried out.In the blasting tests,four kinds of charge structures were used: the the whole paragraph charge structure,the bottom air interval charge structure,the upper air interval charge structure and the structure that the section of the blasthole located in cave were not charged.Counted and comparative analyzed the blasting effects after blasting.It was concluded that the blasting effect of the blasting used upper air interval charge structure was best,compared with the other three c harge structures.The reasons were that its blasting fragmentation was more uniform and had the medium size,and the rates of the small blocks and large blocks were both low.Second,based on the blasting test above,ANSYS/LS-DYNA—the limited element analysis software was used to simulate the blasting test,and it obtained the same conclusion with blasting tests.It verified the feasibility and rationality of numerical simulation method and the selection of parameters used in numerical simulation.Finally,the locations of the cave were changed(located at the middle of blasthole and upper of blasthole).ANSYS/LS-DYNA was used to simulate the blasting with different air interval charge structures.After analyzing the the pressure and the action time of the different elements in blastholes,the blasting effect of each model was speculated.It concluded that the charge structure that could make the blasting effect best was the middle air interval charge structure when the caves were located at the middle and up per of blastholes.Through studies by blasting tests and numerical simulation,it was concluded that when the cave was located at the bottom of blasthole,the charge structure that could make the blasting effect best was the upper air interval charge structure;when the cave was located at the middle and upper of blastholes,the charge structure that could make the blasting effect best was the upper air interval charge structure.