SHOTFIRING

Question 1

STAB HOLES

Answer 1

Used to fragment material in the stemming zone of a blast.

Question 2

NOx

Answer 2

Multiple combinations of oxides of nitrogen (N20, NO, NO2, N204, N203, N205) with nitrogen dioxide (N02) being the principal hazardous nitrous gas.

Question 3

ANFO

Answer 3

A mixture of ammonium nitrate and fuel oil

Question 4

DUST

Answer 4

Airbourne particulate matter ranging from 10 to 50 microns

Question 5

POST BLAST GASES

Answer 5

Gases generated by the detonation of explosives during blasting.

Question 6

PRECURSOR

Answer 6

A material resulting from a chemical or physical change when two or more substances consisting of fuels and oxidisers are mixed and where the material is intended to be used exclusively in the production of an explosive.

Question 7

SLEEP TIME

Answer 7

The time between explosives being loaded into a blast hole and their initiation.

Question 8

RECHARGE

Answer 8

Re-entry of water back into a blast hole after it has been dewatered.

Question 9

GAS BAG

Answer 9

An inflatable bladder used to block off a blast hole and support explosives or stemming.

Question 10

AIR BLAST OVERPRESSURE LIMITS

Answer 10

The recommended maximum level for air blast overpressure is 115db (Lin peak). The level of 115db may be exceeded on up to 5% of the total number of blasts over 12 months. However the level should not exceed 120db (Lin peak) at any time.

Question 11

GROUND VIBRATION

Answer 11

Shockwave / gound movement from blasting with explosives.

Question 12

GROUND VIBRATION LIMITS

Answer 12

The recommended maximum level for ground vibration is 5mm/sec (peak particle velocity). The level of 5mm/sec may be exceeded on up to 5% of blasts in a 12 month period . The level should not exceed 10mm/sec at any time.

Question 13

DOWN HOLE DELAY

Answer 13

600m/s downhole delays used at Bengalla to control the timing between the surface detonation at the blast hole and the primer detonation in the hole. Down hole delays are used to ensure the blast hole initiation / burning front is well in front of the disrupted ground. This reduces the chance of holes or IE being cut of by the disrupted ground.

Question 14

FUME COLOURS

Answer 14

NOx is invisible, nitrogen dioxide ranges from yellow to dark red depending on the concentration and size of gas cloud. These gases are toxic.

Question 15

CAUSES OF HIGH NOx

Answer 15

Fuel deficiency in the explosive or detonation reactions that do not continue to completion (incomplete detonation).

Question 16

NOx GENERATING CONDITIONS MAY BE THE RESULT OF?

Answer 16

1) Explosive formulation and quality assurance
2) Geological conditions
3) Blast design
4) Explosive product selection
5) On bench practices
6) Contamination of explosives in the blast hole

Contamination may be from

1) Water
2) Mud
3) Fallback

Question 17

NOx CAUSES

Answer 17

Explosive type
Inadequate mixing of raw materials
Explosive product seeping into cracks down the hole
Dynamic water in holes
Moisture in clay
Chemicals of rock e.g. limestone
Explosive desensitisation due to blast hole length
Inappropriate priming or placement
Mismatch of explosives and rock type
Primer of insufficient strength to initiate explosive column
Explosive product mixes with mud or sediment at the bottom of the hole
Water entrainment in explosives product
Moisture in ground
Rainfall on a sleeping shot
Contamination of explosives by drill cuttings during loading