Linear Explosive Charge
Calculate the linear loading density of a blast hole, q = (π/4) × d² × ρ, from the hole diameter d (mm) and the explosive density ρ (g/cm³). The result, in kg of explosive per meter of hole, is how much explosive fits in each meter of charged column — a central parameter of rock blast design. Multiplied by the hole charge height, it gives the charge per hole; combined with the blasted rock volume, it gives the powder factor. Larger diameters and denser explosives raise the linear charge. Enter the hole diameter and the explosive density.
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Linear explosive charge
In rock blasting, a pattern of holes is drilled in the bench, each hole is loaded with explosive and the round is fired in sequence. The linear charge (or loading density) answers one question: how much explosive fits in each metre of blasthole? It is q = (π/4) × d² × ρ, simply the cross-sectional area of the hole (πd²/4, from the diameter d) multiplied by the density of the explosive ρ. The result is kilograms of explosive per metre of charged column. The formula shows the strong dependence on the diameter squared: larger holes carry far more explosive per metre (and therefore allow wider burden and spacing and higher production, the trend in the big open-pit mines, which drill 200-300 mm holes). The density of the explosive matters too: emulsions and dynamites (ρ ~1.1-1.3) load more than ANFO (~0.8). Linear charge is the starting point of the charge calculation for a blast: multiplied by the charged length of the hole (which is never the whole hole — the top takes the inert 'stemming'), it gives the charge per hole (kg); summed over every hole and divided by the volume of rock broken, it gives the powder factor (kg/m³) — the key indicator that ties the amount of explosive to the fragmentation obtained. Loading correctly is essential: too much explosive throws flyrock and generates airblast and ground vibration; too little leaves boulders and hard toe. Enter the hole diameter and the density of the explosive.
Related Tools
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.
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.
Blast Subdrilling
Calculate the subdrilling of a blast hole, S_p = 0.3 × B, multiplying the burden B by a typical factor of 0.3. The result, in the unit of B, is the length the hole must drill below the desired bench floor level. This extra depth ensures the blast fragments the rock down to the floor level, avoiding toes (ledges of unfragmented rock at the bench foot) that hinder equipment operation. Insufficient subdrilling leaves toes; excessive wastes drilling and explosive and damages the rock below the floor. Enter the burden.
Specific Fire Load
Calculate the specific fire load of a space, q = (mass × LHV) ÷ area, dividing the total energy of the combustible materials (mass × lower heating value) by the floor area. The result, in MJ/m², is the heat that would be released per unit area if all the material burned — the parameter that classifies a building's fire risk and sets protection requirements (fire resistance, exits, sprinklers) in fire codes. The higher the fire load, the more severe the potential fire. Enter the fuel mass, the heating value and the area.
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.
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.
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.