Blasting safely with proper Blasting safely with proper techniquestechniques

Module oneModule one

• The most important responsibility of the blaster in charge is to prepare and fire safely. They are to practice safety in transportation, storage, handling, and the proper use of explosives.

Module TwoModule TwoPreparing and using blast design.Preparing and using blast design.

• (a) Identify characteristics of overburden-material which lies above the deposit of material desired. Rock quarry may identify this as waste.

• (b) Hard to break rock looks regular in shape and easy to break rock looks shattered and broken. Drill penetration is a good indication of hardness. If drill penetrates 4 to 5 feet per minute the rock is soft. If drill vibrates and is noisy rock is hard.

• (c) Determine the size and drill pattern of the blast. Three common patterns are square, rectangle, and staggered. Keep blasting rate up with the production rate. When choosing patterns know faces and cuts, and know order of shot.

• (d) Choose the type of blasting agent or explosives. Most important is if hole is wet or dry. Bulk ANFO is most common.

• (e) Benching - the process of excavating where terraces or ledges are worked in step patterns.

• (f) Burden =2.5xHole diameter, or, B=30xd/12 can be 24,30,36

• (g) spacing=1.5x burden, or, s=bx1.2 to 1.8• (h) stemming=.7xburden, or, st=.7 to 1.x burden• (i) powder factor=pounds of powder/cubic yards of rock.• (j) compute scaled distance factor- w=(d/ds)2 w=weight

of explosives. D=distance in feet. Ds=scaled distance on chart. 0-301 feet is 50. 301-5000 feet is 55. 5001 feet and beyond is 65.

• (k) Cubic yards per hole = burden x spacing x face height / 27

• (l) pounds of explosives per hole is cubic yards per hole times selected powder factor = pounds per hole.

• (m) Loading density (lb./ft.=.34 x density x diameter squared.

• (n) Total lbs. of powder/delay=(distance to nearest dwelling/60 squared.)

• (o) A well designed delay patterns can affect the direction that the overburden moves, fragmentation, flyrock, noise, vibration, explosives used, how well the toe is pulled, the condition of the new face.

• (p) deck charges may be used to reduce ground vibrations. If using deck charges, fire the bottom first.

• (q) The four types of firing systems are electric, detonating, nonel, and hercudet. Hercudet is hardly any longer used.

Federal Law RequirementsFederal Law Requirements• Pre blast survey regulation. Federal law requires that a mine

operator conduct a pre blast survey on any home within one-half mile of the permit area, if the owner requests. A report must be submitted to the regulatory authority and to the person making the request.

• Blasting schedule publication. The mine operator must publish a blasting schedule before beginning a blasting program. The blasting schedule must be published in a local newspaper of general distribution. The schedule

• must be distributed to all property owners and utilities within one-half mile of permit area. Copies of the blasting schedules that are sent to residents must be accompanied by information advising the owner of how to request a pre blast survey. The schedule must be republished and redistributed at least every twelve months, or whenever there is a change in the schedule.

• Blasting schedule contents should identify the location of the blasting site and the time periods when blasting will occur. It should also include the methods to be used to control access to the blast site.