Powder factor and fragmentation: the basics for contractors
Powder factor is explosive mass per bank cubic metre or tonne blasted. The formula, a worked blast pattern, and what fragmentation does to load and haul.
How material moves from the face to the tip, and what slows it down. This section covers cycle time, match factor, TKPH, rolling resistance, payload and powder factor, with the formulas and worked examples.
Articles
Load, haul & blast Guide
Truck payload: what overloading and underloading cost
Truck payload under Caterpillar's 10/10/20 policy: no more than 10% of loads over 110% of target, none over 120%, mean at or below target, and the costs.
Load, haul & blast Guide
Haul truck cycle time: the parts and how to measure them
Haul truck cycle time is queue, spot, load, haul, dump and return, plus delays. How to measure each part, with a worked trucks and tonnes per hour example.
- BenchA bench is a single working level in an open pit or quarry, a ledge from whose face ore or waste is dug, bounded by a crest at the top and a toe at the bottom.
- Berm (haul road safety berm)A haul road berm is a bank of material built along the edge of a haul road, or down its centre, to deflect a truck that drifts off its line and to warn the operator that the truck needs to be steered back.
- Burden (blasting)In blasting, the burden is the distance from a blasthole, or a row of blastholes, to the nearest free face the rock can move towards, measured at right angles to the row; in a multi-row pattern it is also the distance between rows.
- Grade resistanceGrade resistance is the extra force a machine must overcome to move up a slope, equal to about 10 kg for every tonne of gross machine weight for each 1% of grade.
- Match factorMatch factor is the ratio of the rate at which trucks arrive at a loader to the rate at which the loader can fill them, calculated as the number of trucks times the time to load one truck, divided by the number of loaders times the truck cycle time.
- Rolling resistanceRolling resistance is the force a haul truck must overcome to roll over the road surface, expressed as a percentage of gross machine weight, where each 1% equals 10 kg of resistance for every tonne the truck weighs.
- Spacing (blasting)In blasting, spacing is the distance between adjacent blastholes in the same row, measured along the row at right angles to the burden.
- StemmingStemming is the inert material, usually drill cuttings or crushed stone, packed into the collar of a charged blasthole above the explosive to keep the gases confined in the rock for as long as possible.
- TKPHTKPH (tonne-kilometres per hour) is a tyre's working limit: the load and speed it can carry before heat build-up damages it.
- Tonne-kilometreA tonne-kilometre (tkm) is the unit of haulage work equal to one tonne carried a distance of one kilometre, found by multiplying the mass moved by the distance it travels.
