Explosive Energy Distribution in Explosive Column Case Study of Some Indian Mines

摘要

Air-deck techniques had revolutionized blasting techniques in last few decades globally.This technique made its application in smooth wall blasting technique,and over the years had been adopted for main production blasting also.Additionally this has been an effective method for stabilizing pit walls,explosives charge distribution as a measure to ensure better fragmentation etc.Chemically activated gas bags,used in conventional air-deck had limited application and restricted usage in highly sensitive areas due to high cost component as well as limited flexibility.While researchers continued with its large number of applications in surface mine blasting,its use was site specific only.Authors in this paper have studied in depth the mechanism of air-gap technique vis-a-vis explosive energy distribution in an explosive column of surface mine blasting.With "energy factor" as a scientific tool to ensure proper level of explosive energy required for fragmentation,displacement etc,was adopted for placement of air-gap in the explosive column.To make the concept user friendly and cost-effective empty plastic bottles were selected for placing air-gap.A number of field trials were undertaken before switching over to its application in production blasting.It is currently in use at some limestone,and one uranium mines in India.At the Tata Steel Iron Ore Mine in Joda,Odisha,India,since last April,this is being in use on regular basis in dry holes.The Joda East Iron Ore,is having very hard to soft strata in its mining excavation plan,and accordingly the use of plastic bottles have been made site specific.After detailed techno-economic evaluation,blast monitoring,the authors could implement this system on regular basis since June 2012.Till date over 35000 used plastic bottles of 70 mm dia.and 280 mm length have been used in most production blasts.An attempt has been made in this paper to present the findings of the Joda East Iron Ore Mines (India) aided by photographs and blast details,in addition to the savings obtained vis-a-vis improvement in productivity,powder factor,reduction in generation of over size boulders,control of vibration level etc.explosive column and also in the sub-grade region of any blast hole.