Advance per Blast (Pull)
Calculate the effective advance per blast (pull) in drill-and-blast tunnelling, advance = L·η, from the drilled hole length L (m) and the blast efficiency η (0-1). Not all drilled depth converts to advance: part is lost because the hole bottoms do not always break fully, leaving a 'socket'. Typical efficiency is 85-95% — depending on the blast pattern, rock type and execution. Advance per blast, times the cycles per day, sets the rock face productivity. Maximizing it reduces cycles and schedule, but very long holes lose drilling accuracy and efficiency. Enter the drilled length and the blast efficiency.
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Advance per Blast (Pull)
In rock tunnelling by drill and blast — the oldest method and still the dominant one in hard rock — every cycle consists of drilling dozens of holes into the face, charging them with explosive, detonating, ventilating, hauling away the broken rock (mucking) and supporting the newly exposed section. The advance per blast, or pull, is how far the tunnel actually progresses with each detonation: advance = L·η, the drilled hole length L times the blast efficiency η. The detail that matters is that η < 1: not every metre drilled turns into advance, because the bottom of the holes does not always break out completely, leaving a stub, or bootleg, that eats into the net gain. Typical efficiency falls between 85% and 95%, depending on the quality of the blast design (hole layout and inclination, type and amount of charge, the delay sequence that progressively creates free faces), on the nature of the rock and on drilling accuracy. The advance per blast, multiplied by the number of cycles per day, sets the productivity of the face and therefore the schedule of the job. There is an engineering trade-off here: deeper holes give longer pulls and fewer cycles, but they lose accuracy and efficiency (drilling deviation grows with hole length) and call for more explosive per round. Optimising the pull — balancing hole length, efficiency and overbreak control — is central to blast engineering. Enter the drilled length and the blast efficiency.
Related Tools
Terzaghi Rock Load Height
Estimate the rock load height over a tunnel crown by Terzaghi's classic method, Hp = Cf·(B + Ht), from the rock load factor Cf (depending on mass quality — ~0 for intact rock to >2 for heavily fractured or swelling rock), the width B and the height Ht of the excavation. Hp represents the loosened rock zone above the tunnel that effectively loads the support — Terzaghi proposed that, due to arching in the mass, only a fraction of the total overburden acts on the lining. This loosening-load model is the historic basis for rock tunnel support design. Multiplying Hp by the unit weight gives the support pressure. Enter the load factor, width and height.
TBM Advance Rate
Calculate a tunnel boring machine's daily advance, advance = PR·U·h, from the instantaneous penetration rate PR (m/h, advance while actively boring), utilization U (0-1, the fraction of time actually boring) and operating hours per day h. The distinction between penetration and utilization is central: penetration depends on geology and cutterhead thrust/torque, but utilization — typically only 30-50% — is limited by ring building, cutter changes, maintenance, muck removal and downtime. Real advance is far below nominal penetration, and improving utilization often pays more than increasing penetration. Enter the penetration rate, utilization and hours per day.
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.
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.
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.
Tunnel Volume Loss
Calculate the volume loss of a tunnel excavation, VL = Vs ÷ (π·D²/4)·100, the percentage ratio between the settlement trough volume per metre Vs (m³/m) and the excavated cross-section area (from diameter D). Volume loss quantifies how much soil 'disappeared' relative to the theoretical tunnel volume — caused by face relaxation, overexcavation, tail-gap closure behind the TBM shield and consolidation. It is the key control parameter for urban excavation: well-run EPB/slurry TBMs achieve 0.5-1.5% in soils; values above 2-3% indicate problems and excessive settlement. Enter the trough volume and the tunnel 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.