Blast Hole Count
Calculate the number of holes of a blast pattern, N = area ÷ (burden × spacing), dividing the bench area to blast by the pattern area of each hole (burden B × spacing S). The result is the number of holes needed to cover the area with the specified drilling pattern. In practice, round up. It is an essential quantity calculation in blast planning: it sets the drilling time, the amount of explosive and accessories, and the operation cost. Wider patterns (larger B and S) reduce the number of holes but may worsen fragmentation. Enter the area, the burden and the spacing.
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Blast hole count
In planning a blast, once the drill pattern geometry is set (the burden B and the spacing S between holes), the essential take-off question is: how many holes will be needed? The calculation is N = area ÷ (B × S), dividing the bench area to be blasted by the pattern area of each hole (every hole covers an area equal to burden × spacing around it). In practice the figure is rounded up and adjusted at the edges of the area. This simple number drives the whole planning and budget of the operation. It sets the drilling time (hole count × metres per hole ÷ drill rig productivity), the explosive consumption (hole count × charge per hole), the quantity of initiation accessories (detonators, detonating cord, delays - one or more per hole), and the labour and equipment required. Multiplying the hole count by the volume broken per hole (B × S × bench height) gives the total volume to be blasted in that round. One trade-off sits at the centre: more open patterns (larger B and S) cut the hole count, the drilling and the cost - yet they tend to worsen fragmentation (more oversize boulders), which raises loading, haulage and crushing costs downstream. The optimal pattern therefore minimises the total cost of the chain (drilling + blasting + loading + crushing), not the blasting cost alone. Enter the area, the burden and the spacing.
Related Tools
Blast Burden
Calculate the burden of a blast pattern, B = k × d, multiplying a factor k (typically 25 to 40, depending on rock and explosive) by the hole diameter d. The result, in the unit of d, is the distance from the row of holes to the free rock face — one of the most critical geometric parameters of blasting. Too large a burden leaves the rock poorly fragmented (boulders) and creates toes; too small wastes explosive and causes flyrock and overpressure. Together with the hole spacing, the burden defines the drilling pattern and the resulting fragmentation. Enter the factor k and the hole diameter.
Mean Fragment Size (Kuz-Ram)
Estimates the mean fragment size X₅₀ of a blast with the Kuz-Ram model, from the rock factor, the volume broken per hole, the explosive mass per hole and the relative weight strength of the explosive. It is the screen size half the muckpile passes, the number that decides whether crushing will struggle. Enter the four blast design parameters.
Powder Factor
Compute the powder factor of a rock blast by dividing the explosive mass (kg) by the volume of rock broken (m³), in kg/m³. It is the central parameter of the blast design: too low produces boulders and poor fragmentation; too high wastes explosive and increases vibration and flyrock. Optimizing it reduces downstream crushing costs. Enter the explosive mass and the rock volume.
Hedström Number
Calculates the Hedström number (He), a dimensionless group combining density, yield stress, pipe diameter and plastic viscosity of a Bingham fluid. Used together with the Bingham Reynolds number, it locates the laminar-to-turbulent transition for drilling fluids, mineral slurries and cement pastes. Enter the four quantities.
Detonation Velocity (VOD)
Calculate the velocity of detonation (VOD) of an explosive, VOD = L ÷ t, dividing the distance traveled by the detonation wave L (m) by the time t (s) measured between two sensors. The result, in m/s, is the speed at which the detonation reaction propagates through the explosive column — one of the most important properties of an explosive, linked to its energy and fragmentation power. High-VOD explosives (4000-7000 m/s, like emulsions and dynamites) generate high detonation pressure and are effective in hard rock; low VOD (ANFO, ~3000-4500 m/s) suits softer rock. Enter the measured distance and time.
Number of Sprinklers
Calculate the number of automatic sprinklers needed, N = area ÷ coverage area per head, dividing the total area to protect (m²) by the maximum coverage area of each sprinkler (m²). The result is the minimum number of heads to cover the space, spaced within code limits (coverage per head depends on hazard class and sprinkler type). In practice, always round up and adjust to the piping and beam layout. It is an initial quantity calculation in sprinkler system design. Enter the area to protect and the coverage area per head.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.