Lec12 - Explosives and Blasting - I - F2023-part-2.pdf

Mining Optimization Laboratory Blast Design 27 • Primary goal: – Safe, efficient and productive blasting; – Effective in rock fragmentation and lowest overall operation cost associated with the blast. • Good blast performance requires controlled release of explosive energy; • Energy release cont...

Mining Optimization Laboratory Blast Design 27 • Primary goal: – Safe, efficient and productive blasting; – Effective in rock fragmentation and lowest overall operation cost associated with the blast. • Good blast performance requires controlled release of explosive energy; • Energy release controlled by: – Design layout, – Hole loading procedures, – Detonation sequence. 27 Highwall Stability • A safe and stable highwall is critical to all aspects of a blasting operation. – Equipment, blasting crews and shovel operators. • Maintaining a stable highwall requires a good understanding of: – – – – 28 Ahlam Maremi Geology, Water conditions, Slope, and Blast design. 28 Mining Optimization Laboratory Definition of Bench Blasting Terms 29 • Burden: – It is the distance from a single row to the free face of the excavation, or between rows. – The proper burden dimension to use a function of hole diameter, relative rock density, and the explosive that will be used in the blast. • Too small a burden can result in excessive air-blast and flyrock; • Too large a burden can result in improper fragmentation, toe problems, and excessive ground vibrations. • The burden, in turn, is the basis for calculating spacing, stemming, and sub-drilling. 29 Definition of Bench Blasting Terms • Spacing: – Spacing is the distance between adjacent blastholes in a row, measured perpendicular to the burden. • In row-to-row shooting, spacing is measured between holes in a row; • When the shot progresses at an angle to the free face, the spacing is measured at that angle. – Spacing is a function of the burden, sometimes dependent on the timing. • Close spacings cause crushing and cratering between holes, boulders, and toe problems. • Wide spacing will result in inadequate fragmentation. 30 Ahlam Maremi 30 Mining Optimization Laboratory Definition of Bench Blasting Terms 31 • Stemming: – Stemming contains explosive energy within a blasthole, so that it will break and move the rock without generating flyrock. • We can use sized crushed stone or drill cuttings as stemming materials. 31 Definition of Bench Blasting Terms • Sub-drilling: – It is the distance drilled below the floor level (or the actual required blast depth) to ensure that the full face of the rock is capable of being removed to the desired excavation limit. – Subdrilling may be required to achieve a smooth pit floor. – The subdrill portion of a borehole is generally backfilled with drill cuttings or other stemming material. – Usually, we do not load explosives into the subdrill! – 32 Ahlam Maremi https://www.linkedin.com/posts/hooman-askari-019aa130_greatshots-activity-6991440585031118849R97G?utm_source=share&utm_medium=member_desktop 32 Mining Optimization Laboratory Learning Outcomes 33 By the end of this lecture you know: – The importance steps of the rock fragmentation process by blasting: • Compression waves pressure, reflection of the pressure wave and gas pressure – The three main factors that influence rock breakage • Drilling, explosives and geology – Some explosives blasting agents available • Must select adequate product according to field conditions – The main properties of explosives that will influence the explosives selection (depending on specific applications) – And understand that the key ingredient for selection is the ability to safely obtain the lowest unit cost of material produced • Effective blasting – Bench Blasting Terms 33 Don’t Forget! • • • • • 34 Ahlam Maremi Check your LU email and D2L regularly. Review additional resources available on D2L Guest Lecture on Oct 31st – Rescheduled on Nov 7th Quiz 2 on Nov 7th Final Exam Dec 7th B-GYM – Lec10 to the end 34