Blast Design Calculator · Forge

Bench geometry

Burden and spacing are the design values at the collar, measured perpendicular to the face and along it.

Hole diameter mm Bit size, not the charge diameter.

Bench height m Vertical crest to floor. Not the drilled length.

Burden m

Spacing m

Pattern Staggered offsets alternate rows by half a spacing.

Subdrill m Measured along the hole, below floor grade.

Stemming m

Hole angle ° from vertical Many designers quote this from horizontal instead. Vertical is the reference here.

Rows count

Holes per row count

Explosive and rock

Density and velocity of detonation set the energy and the borehole pressure. Rock density converts volume to tonnes.

Explosive product Selecting a product loads its nominal density and VOD. Both stay editable.

Explosive density g/cc

Velocity of detonation m/s In-hole VOD at this diameter, not the ideal or tested value.

Rock density t/m³

UCS MPa Sets the powder-factor band the design is compared against.

The design

Everything the rest of the suite consumes comes from these numbers.

Design rules

Published ranges, not pass/fail. Sitting outside one is a decision you should be able to defend, not an error.

Plan view

Drawn to scale from the geometry above. Grid north is up; the free face is the heavy line.

Bench section

One hole in profile, on the section normal to the face. The face is assumed battered parallel to the holes.

Powder factor against burden

Charge mass per hole is held fixed. Burden is swept ±40% about the design.

Derived quantities

Ratios

dimensionless

Conventions in force

Where this design sits

Sources

what each band is from

Unit rates

yours, not ours

Explosive $/kg

Drilling $/m

Accessories $/hole

Stemming aggregate $/t

Aggregate bulk density t/m³ Loose bulk density of the crushed stemming, not the solid rock density.

Stemming wastage % Spillage, overfill and what the loader leaves. Ordered tonnage is the placed tonnage plus this.

Rates default to blank on purpose. Drill-and-blast cost per tonne is a commercial number that belongs to your contract and your fleet, and a plausible default would be quoted back at you as though this tool had produced it. Enter your own and the arithmetic is done here.

Quantities

Cost

Enter at least one unit rate above and the quantities are costed here.

Nothing is assumed. There is no default explosive price, no default drilling rate and no benchmark dollars-per-tonne in this tool, because a number like that would be read as ours and quoted as though Forge had produced it. The rates are yours; the arithmetic is ours.