Every term you will meet on a monitoring job, explained in one sentence first. Tap a term anywhere on the site to see it.
Ground moving back and forth in one smooth, steady rhythm.
Picture itA child on a swing: same height each time, same time for each swing, over and over.
PreciselyA single sine wave with one frequency and one amplitude. Real blast vibration is many tones at once; the pure tone is the building block we use to explain them.
On siteThe concept pages and the vibration calculator use a pure tone so the numbers can be checked by hand.
One complete back-and-forth movement of the ground.
Picture itOut, back, out the other way, and home again. That is one cycle.
PreciselyOne full repetition of a periodic motion, from a point in the wave to the next time it returns to the same point moving the same way.
On siteFrequency counts cycles per second. The trace stack on the concept pages shows two of them.
How long one cycle takes.
Picture itA 20 Hz vibration finishes a cycle every fiftieth of a second: 50 milliseconds.
PreciselyThe time for one full cycle, T = 1 / f. Period and frequency are the same fact written two ways.
On siteThe scene scrubber shows the period as milliseconds per cycle.
How many cycles the ground completes each second.
Picture itA slow rocking is a low frequency. A buzz is a high one.
PreciselyCycles per second, measured in hertz. It is the factor that turns displacement into velocity and velocity into acceleration.
On siteA report quotes the dominant frequency next to PPV, and most limits change with it.
Related: Hertz (Hz), Period, Dominant frequency
The unit for frequency: one hertz is one cycle every second.
Picture itGround at 10 Hz swings back and forth ten times a second.
PreciselyThe SI unit of frequency, symbol Hz. Blast vibration mostly sits between 2 and 250 Hz.
On siteSettings screens and reports write frequency in Hz.
How big the movement is: the furthest the ground gets from rest.
Picture itHow high the swing goes, not how often.
PreciselyThe maximum value of a wave measured from its rest position. Displacement, velocity and acceleration each have their own amplitude.
On siteThe peak value in a report is the amplitude of the recorded wave.
The single largest value in a record.
Picture itThe tallest point on the trace, whichever way it points.
PreciselyThe maximum absolute value of a quantity over the record, as opposed to an average or a value at one instant.
On siteCompliance is judged on peaks. PPV is the peak of velocity.
Related: Amplitude, PPV, Peak vector sum
The rate at which something is changing.
Picture itIf displacement is where the ground is, velocity is how fast that is changing, and acceleration is how fast the speed is changing. Same motion, three views.
PreciselyThe instantaneous rate of change of a quantity with respect to time. Velocity is the derivative of displacement; acceleration is the derivative of velocity.
On siteThe platform converts between g and mm/s using this relationship at a given frequency.
Related: Displacement, Velocity, Acceleration
How far the ground has moved from where it rests.
Picture itA speck on the surface slides a tenth of a millimetre and back. That distance is displacement.
PreciselyThe position of a ground particle relative to its rest position, measured in millimetres.
On siteRarely used in limits because the numbers are tiny. It is the quantity you can see in the scenes.
How fast the ground is moving at one instant.
Picture itThe speck moves fastest as it passes through the middle and stops at each end.
PreciselyThe rate of change of displacement, measured in millimetres per second. Its peak is PPV.
On siteLimits are written in mm/s. A geophone senses velocity directly.
Related: Displacement, Acceleration, PPV
How quickly the ground's speed is changing.
Picture itThe jolt you feel when a lift starts or stops. Bigger jolt, bigger acceleration.
PreciselyThe rate of change of velocity, measured in g or mm/s². It is largest where the ground stops and reverses.
On siteA ViB senses acceleration and triggers on it. The platform converts it to velocity for the report.
Related: Velocity, g, Accelerometer
A unit of acceleration: 1 g is the pull of gravity.
Picture itDrop a phone and it accelerates at 1 g. A ViB trigger is a tiny fraction of that.
Precisely9.80665 metres per second squared. An accelerometer's range and trigger threshold are written in g.
On siteThe trigger chart turns a g threshold into mm/s at each frequency.
Related: Acceleration, Trigger
Millimetres per second: the unit for ground velocity and for most limits.
Picture itTen mm/s is the ground moving as fast as a slow snail, for a moment.
PreciselyThe unit of particle velocity used by Australian and most international blast standards.
On siteEvery limit on a compliance chart is in mm/s.
Peak particle velocity: the fastest the ground moved during the whole record.
Picture itNot the speed at one chosen moment, the biggest speed anywhere in the record.
PreciselyThe maximum absolute velocity in a record, usually reported per axis and as a peak vector sum.
On siteThe headline number on every vibration report.
Related: Peak, Velocity, Peak vector sum, Limit
The largest combined speed across all three directions at once.
Picture itThe ground moves sideways and up at the same time; add the directions together and take the biggest moment.
PreciselyThe maximum over the record of the square root of the sum of squared axis velocities at each instant.
On siteReports show PVS next to the three axis PPVs.
The wiggly line that shows the ground motion over time.
Picture itLike a heartbeat trace: time runs left to right, the line moves up and down.
PreciselyA time-series plot of a recorded quantity. Also called a trace.
On siteThe analyser shows one waveform per axis.
Related: Pure tone, Spectrum, Record time
The three directions a blast report uses: across the path, up and down, and along the path.
Picture itStand facing the blast: Long runs towards you, Tran runs side to side, Vert runs up and down.
PreciselyTransverse, vertical and longitudinal components of ground motion, relative to the line from the blast to the monitor.
On siteA geophone set level and aimed reads them directly; a ViB works them out from gravity and its own record.
Related: PPV, Peak vector sum, Particle motion
The path a point of ground takes as it shakes, in all three directions at once.
Picture itFollow the tip of the ground’s speed as it swings: over a blast it draws a loop.
PreciselyThe path of the three-component velocity over time, often plotted as a hodogram.
On siteThe loop is stretched along the way the motion travelled, which is how a ViB finds Long.
Related: Peak vector sum, Tran, Vert, Long
How many readings the unit takes each second.
Picture itA film at 24 frames a second looks smooth; a unit at thousands of samples a second catches every wiggle.
PreciselyThe number of samples per second in a recording, in hertz or samples per second. It must be well above the highest frequency of interest.
On siteFixed by the unit. It is not the frequency of the ground.
Related: Resolution, Record time, Frequency
The level of shaking that makes the unit start recording.
Picture itA tripwire: quiet ground does nothing, a blast crosses the line and the unit records.
PreciselyA threshold on the sensed quantity above which a recording begins. On a ViB it is set as a share of the g range.
On siteThe settings screen shows the trigger, and the trigger chart shows what it means in mm/s.
Related: Pre-trigger, g, Record timeOpen the guide: Setting a ViB up for a blast
The moment before the trigger that the unit keeps anyway.
Picture itA dashcam that saves the seconds before the bump.
PreciselyA buffer of samples retained from before the trigger crossing, so the record shows the first arrival.
On siteSet in the recording settings. It costs record time.
Related: Trigger, Record timeOpen the guide: Setting a ViB up for a blast
How long the unit keeps recording after it triggers.
Picture itLong enough to catch the whole blast, plus a little, and no longer.
PreciselyThe duration of the recording after the trigger, chosen to cover the event and its decay.
On siteThe set-up guide shows how to pick it for a blast.
Related: Trigger, Pre-trigger, Sample rateOpen the guide: Setting a ViB up for a blast
The main rhythm in a record.
Picture itA crowd chanting: many voices, one beat you can hear above the rest.
PreciselyThe frequency carrying the most energy in a record, found by zero-crossing analysis or a spectral peak.
On siteQuoted next to PPV on the report, because the limit depends on it.
A record broken down into the frequencies inside it.
Picture itA chord split into its notes.
PreciselyA frequency-domain view of a record, usually from a Fourier transform, showing amplitude at each frequency.
On siteThe analyser shows a spectrum alongside the waveform.
Related: Dominant frequency, Waveform, Frequency
The shaking was bigger than the unit could measure, so the top is cut off.
Picture itTurning a stereo up until the sound distorts.
PreciselySaturation of the sensor or converter at the edge of its range. The peak is unknown and the record is flagged.
On siteThe trigger chart shows the clip line; choose a range above it.
The smallest change the unit can tell apart.
Picture itA ruler marked in millimetres cannot show half a millimetre.
PreciselyThe smallest step in the measured quantity, set by the sensor range and the converter's bit depth.
On siteA wider range means coarser resolution. Pick the range for the blast, not the biggest.
Related: Sample rate, Clipping
A sensor that measures how fast the ground moves.
Picture itA magnet on a spring inside a coil: the ground moves, the magnet lags, a voltage appears.
PreciselyA velocity transducer. It reads mm/s directly but has a low-frequency roll-off.
On siteThe traditional blast monitor sensor. ShotTrack ViB uses an accelerometer instead.
Related: Accelerometer, Triaxial, Tran, Vert, Long
A sensor that measures how quickly the ground's speed changes.
Picture itThe same chip that tells your phone it has been turned sideways.
PreciselyA MEMS transducer that outputs acceleration in g. Velocity is derived from it at each frequency.
On siteThe sensor inside a ViB. Its trigger and range are set in g.
Related: Geophone, Acceleration, ViB
ShotTrack's vibration monitoring unit.
Picture itA box you set near the thing you must not shake too much.
PreciselyA self-contained accelerometer-based blast vibration monitor that records triggered events and syncs to the ShockAI platform.
On siteThe set-up guide walks through placing and configuring one.
Related: Accelerometer, Trigger, VoDOpen the guide: Setting a ViB up for a blast
Velocity of detonation: how fast the explosive itself burns through the hole.
Picture itThe speed of the flame front down the column, in kilometres per second.
PreciselyThe propagation speed of the detonation front along an explosive column, measured with a resistance wire.
On siteShotTrack VoD units measure this; it is a different measurement from ground vibration.
Related: ViB
Measuring in three directions at right angles, all at once.
Picture itThree sensors in one case, each pointing a different way, like the corner of a box.
PreciselyThree orthogonal sensing axes in one instrument.
On siteBlast monitors are triaxial: a geophone has three coils, a ViB one chip that reads three ways.
Related: Geophone, Accelerometer, Tran, Vert, Long
The most shaking a blast is allowed to cause at a place.
Picture itA speed limit for the ground, set for the house next door.
PreciselyA maximum PPV, usually depending on frequency and on what is being protected, set by a standard or a licence.
On siteReports compare the recorded peak against the limit.
Related: PPV, Standard, Dominant frequency
The rulebook that says how to measure vibration and what limits apply.
Picture itThe written rules the regulator and the mine both agree to follow.
PreciselyA published document such as AS 2187.2 that defines measurement practice and human-comfort or structural limits.
On siteThe compliance charts follow the standard chosen for the project.
Far enough from the blast that the shaking is small and smooth.
Picture itStanding across the road from a concert rather than beside the speakers.
PreciselyDistances at which vibration is low-frequency, low-amplitude and dominated by surface waves, as opposed to the near field close to the charge.
On siteNeighbour monitoring is far-field. Near-field records need a wider range.
Related: Displacement, Limit, Dominant frequencyRead the concept: Displacement
The pressure wave in the air from a blast, felt as a thump.
Picture itThe window rattle, not the ground shake.
PreciselyAir overpressure from the blast, measured in decibels (linear) with its own limits.
On siteMeasured with a microphone channel, separately from ground vibration.
Related: Limit, Standard, Overpressure, Stemming
The rock in front of a hole: the distance from the hole to the free face.
Picture itStand at the face and walk to the first row. That walk is the burden.
PreciselyThe perpendicular distance from a charge to the nearest free face, or between successive rows, in metres.
On siteToo little throws rock; too much leaves a hard toe and shakes the ground more.
Related: Spacing, Bench height, Powder factor
The distance between two neighbouring holes in the same row.
Picture itWalk along a row from one collar to the next.
PreciselyThe centre-to-centre distance between adjacent holes along a row, in metres; usually a little larger than the burden.
On siteToo wide and the rock between two holes stands as a hump.
Related: Burden, Powder factor
How tall the step of rock is from the floor to the top of the bench.
Picture itThe height of the wall the blast will bring down.
PreciselyThe vertical distance from the bench floor to the collar surface, in metres; the hole depth is this plus the sub-drill.
On siteSets the charge column length and the block of rock each hole breaks.
Related: Burden, Sub-drill, Charge column
The plug of crushed rock in the top of a hole that keeps the blast's energy in the ground.
Picture itA cork in a bottle, made of gravel.
PreciselyThe uncharged length at the collar, filled with inert material, in metres.
On siteShort stemming means loud airblast and flyrock; the collar is where a blast vents.
Related: Charge column, Airblast
The part of a hole drilled past the bench floor so the charge breaks the floor cleanly.
Picture itDrilling a little deeper than the step you want to break.
PreciselyThe hole length below the planned floor level, in metres.
On siteToo little leaves a hard toe; too much shakes the ground for nothing.
Related: Bench height, Charge column
The explosive in one hole, from the top of the charge down to the toe.
Picture itA long thin cylinder of explosive standing in the hole.
PreciselyThe charged length of a hole, whose mass is the hole's cross-section times that length times the explosive density.
On siteCrews load to a length; the mass follows from the diameter.
Related: Stemming, Hole diameter, Powder factor
How wide the drilled hole is.
Picture itThe width of the bit that drilled it, from a coffee cup to a dinner plate.
PreciselyThe drilled diameter in millimetres; the charge mass per metre grows with its square.
On siteA slightly wider hole holds noticeably more explosive.
Related: Charge column, Burden
The charge in one hole divided by the block of rock that hole breaks.
Picture itKilograms of explosive for every cubic metre of rock.
PreciselyCharge mass over burden times spacing times bench height, in kilograms per cubic metre, or per tonne through the rock density.
On siteThe first number an engineer checks against the rock type.
Related: Charge column, Burden, Spacing
The gap in time between one hole firing and the next.
Picture itDominoes falling a set beat apart.
PreciselyThe nominal interval between successive detonations, in milliseconds, set by the initiation system.
On siteThe cheapest thing to change on a blast and the biggest lever on vibration.
Related: Inter-hole delay, Inter-row delay, Initiation system
The delay between two neighbouring holes in the same row.
Picture itThe beat along a row.
PreciselyThe nominal firing interval between adjacent holes in a row, in milliseconds; 17 ms is a common figure.
On siteShorter than the MIC window and two holes count as one charge.
Related: Delay, Inter-row delay, Isochrone
The delay between one row firing and the row behind it.
Picture itThe pause that lets a row move before the next one fires.
PreciselyThe nominal firing interval between successive rows, in milliseconds; usually several times the inter-hole delay.
On siteToo short and the back row fires into rock that has not moved yet.
Related: Delay, Inter-hole delay, Burden
A line across the bench joining the points that fire at the same instant.
Picture itContour lines, but for time instead of height.
PreciselyA contour of equal nominal firing time drawn over the hole lattice; its spacing shows how fast the firing front moves.
On siteWhere the lines bunch up, holes are firing close together.
Related: Delay, Inter-hole delay
The path the firing signal takes from the start point to every hole.
Picture itWiring a string of lights so each one lights the next.
PreciselyThe connection order of surface delays: along each row hole by hole, and between rows on a control line.
On siteOn shock tube the tie-in is the path a cut-off follows.
Related: Shock tube, Initiation system, Cut-off
How the firing signal reaches each hole and how well each hole keeps its planned time.
Picture itThe wiring and the clocks of the blast.
PreciselyElectronic units with a programmed delay, shock tube with fixed surface and downhole delays, or electric caps in a fixed series.
On siteElectronic holds a fraction of a millisecond; the others drift by a few.
Related: Electronic detonator, Shock tube, Tie-in
A detonator with a clock inside, programmed to fire at an exact time.
Picture itAn alarm clock in every hole.
PreciselyA programmable unit fired by a coded signal, accurate to well under a millisecond, that logs its own firing time.
On siteThe det log it produces is what ShockAI compares with the plan.
Related: Initiation system, Delay
A thin plastic tube that carries the firing signal from hole to hole as a small flash.
Picture itA fuse that runs in a tube at a mile a second.
PreciselyA non-electric initiation system: surface connectors in fixed delays feed downhole units, and the timing drifts a little at each step.
On siteCheap and robust, but no log and the line can be cut.
Related: Initiation system, Tie-in, Cut-off
A hole that did not fire.
Picture itA domino that stayed standing.
PreciselyA charged hole that failed to detonate, for any reason, leaving its explosive in the ground.
On siteLess vibration than planned, and a live charge in the muck.
Related: Cut-off, Charge column
A line cut by moving rock before the signal has passed, so the holes behind it never fire.
Picture itSomeone stepping on the fuse.
PreciselyOn a shock-tube tie-in, the loss of every hole downstream of a break in the surface line caused by ground already broken.
On siteThe reason the downhole delay must outlast the surface run.
Related: Shock tube, Misfire, Tie-in
Maximum instantaneous charge: the biggest mass of explosive that fires together inside one short window.
Picture itNot the whole blast, only the holes that go off within about eight thousandths of a second of each other.
PreciselyThe largest total charge mass detonating within any window of the regulatory width, usually 8 ms; the charge term in the scaled-distance law.
On siteLonger delays lower it without touching the pattern.
Related: Scaled distance, Inter-hole delay, Delay
The distance to the monitor divided by the square root of the charge that fires together.
Picture itFar away and small are the same thing to the ground.
PreciselyD divided by the square root of the MIC, in metres per root kilogram; cube-root scaling is used for airblast and in some jurisdictions.
On siteEvery vibration law is a line against this number.
The line through a site's own vibration readings, used to predict the next blast.
Picture itYour own version of the textbook line, drawn from your own dots.
PreciselyPPV = K · (D/√W)^−β fitted by least squares in log-log space to a project's readings, with a prediction band from the residual scatter.
On siteDesign to the band, not the line.
Related: Scaled distance, Site constants K and beta, P95, Seed hole
The two numbers that pin a site's line: how high it starts and how fast it falls with distance.
Picture itK says how loud the rock is; beta says how quickly it goes quiet.
PreciselyThe intercept K and the slope magnitude β of the fitted scaled-distance law; 1140 and 1.6 is the common no-data pair for hard rock.
On siteTwo sites with the same K can differ a lot at 500 m if their betas differ.
Related: Site law, Scaled distance
Waves from different holes add up where they meet, so close arrivals make a bigger peak.
Picture itTwo people jumping in step on the same floor.
PreciselyThe recorded trace is the sum of every hole's wavelet, each delayed by its firing time and its travel time to the monitor.
On siteThe usual reason a trace peak beats the single-charge law.
A single hole fired on its own so every monitor reads it cleanly as one reading.
Picture itOne domino at a time instead of the whole run.
PreciselyA campaign hole fired at least a full wavelet's length apart from its neighbours, giving one (charge, distance, peak) reading per monitor.
On siteA morning of seed holes can fit a site law that production blasts take a year to earn.
The level that nineteen readings in twenty stay under.
Picture itNot the middle of the pack, near the top of it.
PreciselyThe upper 95 % one-sided prediction bound of a fitted law, from the residual scatter and Student's t on the fit's degrees of freedom.
On siteThe number to design a charge to; the line itself is beaten half the time.
Too close to the blast for the simple distance law to hold.
Picture itStanding next to a speaker instead of across the room.
PreciselyScaled distances below roughly 2 m/√kg, where the charge is no longer a point source and the law is not fitted or trusted.
On siteA reading from the pit rim may be near field; the law will say so.
Related: Scaled distance, Site law, Far field
How small the rock breaks.
Picture itGravel versus boulders from the same bench.
PreciselyThe size distribution of the broken rock, estimated from powder factor, rock type and pattern (Kuz-Ram), and reported as a mean size and the size 80 % passes.
On siteFiner costs more explosive; coarser costs more at the crusher.
Related: Powder factor, Burden
Rock thrown beyond the muck pile.
Picture itA stone from a catapult.
PreciselyRock projected from the face or the collar, with a range that grows with charge per metre and shrinks with burden and stemming; exclusion zones are set as multiples of it.
On siteShort stemming and thin burden are the usual causes.
The peak air pressure of an airblast, above the normal pressure of the air.
Picture itThe push you feel on your chest from a big door slamming.
PreciselyPeak pressure of the air pulse, quoted in linear decibels re 20 µPa; 120 dB is 20 Pa.
On siteThe number the airblast limit is written against.
Four of these have full pages with moving pictures.Read the concepts
Estimate PPV, acceleration, safe distance and maximum charge from the scaled-distance law.
Open the calculatorHow far the ground moved from rest — usually a fraction of a millimetre.
StartPick the job, read the numbers it needs, and know what the unit will do when the shot fires.
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