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Inspänningens Betydelse för Vibrationsnivån: Etapp 2 Fältförsök
Geosigma.
EDZ Consulting AB.
Swebrec.ORCID iD: 0000-0002-8024-435X
Swebrec .ORCID iD: 0000-0001-8564-3694
Number of Authors: 42016 (Swedish)Report (Other academic)Alternative title
How does confinement affect the vibration level in blasting : Phase 2 Field trials (English)
Abstract [en]

Blasting in urban areas must involve techniques to control the vibration level. Charge confinement is one of the parameters that are believed to influence the vibration level. A charge could be too confined due to:- Incorrect charge calculation (charge weight is too small for the drilled burden)- Incorrect interval-time (holes behind are initiated before holes ahead)- Incorrect selection of explosive for the burden or an influence of dead pressing- Unfavourable selection of geometry- Drill hole deviationA common opinion among blasters is that an increased confinement results in a higher vibration level. Is there a physical explanation for this or is it just a common misunderstanding established a long time ago? A feasibility study was previously conducted and reported in BeFo Report 132, (Niklasson et.al, 2014). The report comprised a literature study and an assessment of a number of observed misfires in tunnels, still with correctly detonating charges but with a reduction of more than 50 % in pull or rock breakage. It also comprised a statistical analysis of some of the rounds. The result of the study found no evidence for a relationship between degree of charge confinement and vibration level.As a result of the feasibility study a field study was proposed. This study was performed in a quarry, some 40 km north of Stockholm, close to Arlanda airport. A number of single holes were blasted; both holes with full breakage and confined holes and the vibration levels were measured.13 single holes with full breakage and 10 totally confined single holes were blasted. The burden was 1.5 m for the holes with breakage and the confined holes had a distance to the free surface of some 15 m. The hole diameter was 45 mm and hole depth 3 m. The holes were charged with a dynamite explosive, Minex Eco, and the charge weight was 1 kg/hole. The charges were initiated with electric detonators. All holes were stemmed.The vibration levels were measured in three holes with a depth of 3 m. In the bottom of the holes thee-axial geophones were grouted. A forth geophone was placed on the surface.Single hole blasting were performed with very good result. The holes close to the surface gave full breakage while the confined holes showed no breakage.The vibration signals were vector summarised and analysed. The distances from each hole to each geophone was determined. The vibration PPV-values were plotted as a function of the distances.The final result showed that there were no significant differences in vibration levels between confined holes and holes with full breakage.Key words: Vibrations, confined holes, blasting, geophones, grouting, quarry

Place, publisher, year, edition, pages
Stockholm: Stiftelsen bergteknisk forskning - Befo , 2016. , p. 53
Series
BeFo-rapporter, ISSN 1104-1773 ; 151
National Category
Other Civil Engineering
Research subject
Mining and Rock Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-23974Local ID: 92773938-da0a-4556-9930-37652e0e3facOAI: oai:DiVA.org:ltu-23974DiVA, id: diva2:997024
Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-05-28Bibliographically approved

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http://www.befoonline.org/publikationer/r151__637

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Beyglou, AliPetropoulos, Nikolaos

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