Mandal, S.K (2009) Impact of Hole Depth on Vibration Magnitude vis-a-vis Minimization of Vibration Level for Safe Opencast Operation. Journal of the Institution of Engineers (India), 90. pp. 8-14. ISSN 0257-442X

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Excavation of locked up coal pillars by opencast method and presence of dwellings in close proximity to such operation needs a specialized drilling and blasting plan for its safe excavation. Introduction of private entrepreneurs sometimes urges the operating personnel and practicing engineers to introduce unsafe blast design parameters with respect to bench height for extraction of coal by opencast method. Implementation of sub-optimal blast design parameters due to mismatched drilling equipment leads to complaints from local inhabitants, damage to structures and even casualties as a result of undesired throw of basted fragments. Comparing magnitude of vibration generated from different drill hole diameters, depth of hole and type of explosive (bulk or cartridge) this paper communicates that a maximum of 110 mm drill diameter and 83 mm cartridge diameter should be implemented for safe excavation, especially when the structures are with in 100m from the place of blasting. Whe3n the structures are between 50m and 100m, depth of blast hole should not be more than 5 m to contain the magnitude of vibration with in safe limit. Due to high coupling factor for bulk loaded explosives, the attenuation rate of vibration for a given range of distance is low and should not be implemented when structures are with in 100m from the place of blasting. For structures beyond 120m from the place of blasting, bulk explosive may be implemented by limiting the bench height. Depth of holes and drill diameter for such cases may be between 8m and 10m and 110 mm and 160 mm, respectively. The paper also communicates that for the excavation work in close proximity to structures, burden should be less than optimum with respect to concerned bench height to contain the magnitude of vibration with the permissible limit

Item Type: Article
Uncontrolled Keywords: Vibration; Depth of hole; Frequency; Attenuation
Subjects: Blasting
Depositing User: Dr. Satyendra Kumar Singh
Date Deposited: 31 Dec 2011 03:58
Last Modified: 13 Dec 2014 05:27

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