Author ORCID Identifier

https://orcid.org/0000-0002-8601-3843

Year of Publication

2020

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Engineering

Department/School/Program

Mining Engineering

First Advisor

Dr. Jhon Jairo Silva-Castro

Abstract

Blasters use the delay between charges and the firing sequence of the explosive charges to help reduce vibrations and achieve the desired fragmentation. Although delay and sequence are recognized as very important for vibrations and fragmentation, only vibration models consider timing as a variable in the prediction tool, without any known model for fragmentation prediction based on the delay sequence. Of the few fragmentation models available, very few take delay into account and do not give guidance on row delay and/or sequence selections. With the invention of electronic detonators in 1984, there are new avenues to explore with sequence and timing. Currently, blasters shoot using a trial and error approach when deciding on what timing to use to optimize fragmentation to the operations’ needs. Experience and trial and error are usually the deciding factors on what delay is selected to get certain fragmentation.

Delay sequence and its influences on fragmentation is the focus of this dissertation. Current fragmentation models look at what is the delay timing between holes. Rarely do they look at the delay timing of the whole shot. Current models also look at a general fragmentation for the shot based on some design parameters. With timing, it is important to look at fragmentation on a hole-by-hole basis. Dynamic confinement (a concept developed in this research) changes drastically with timing. Dynamic confinement is the level of void space in front of a hole that changes with time due to explosives energy and gravity. Changes in dynamic confinement produce important changes in the final fragmentation of the shot. Given the relation between dynamic confinement and timing, it is suggested that the fragmentation be looked on charge by charge and not just design or average for one hole, in contrast to current fragmentation models.

In this research, a conceptual model was created using the proposed dynamic confinement theory to include row timing into fragmentation models. The dissertation looks at previous fragmentation models, the theory behind dynamic confinement, the Worsey-Silva model, and some full-scale testing for validation.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2020.439

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