blast-physics-js

A JavaScript blast physics engine for the mining industry.
Vibration prediction · Damage modelling · Detonation simulation · Flyrock analysis · Blast movement

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What is this?

blast-physics-js is a free, open-source npm library that provides blast engineering models for the mining industry, implemented in pure JavaScript with zero rendering dependencies.

It is the physics companion to Kirra — extracting the analytical models from Kirra's GPU shader pipeline into a standalone, testable, composable library that any mining engineer or software developer can use.

npm install blast-physics-js

Features

• Zero rendering dependencies — no Three.js, no WebGL, no DOM. Pure computational library.
• Isomorphic — runs identically in browser (ES modules) and Node.js (CommonJS).
• SI units throughout — metres, kilograms, seconds, Pascals, m/s.
• Typed array output — all grid computations return Float32Array / Float64Array for direct GPU upload.
• Model fidelity hierarchy — simple site-law PPV through to full Blair & Minchinton time-domain waveform superposition.
• Per-deck architecture — multi-deck holes, air gaps, COUPLED/DECOUPLED charges, and per-product VOD/density are first-class concepts.

Models

Domain	Models	Output
Vibration	PPV, PPV Per-Deck, Scaled Heelan, Blair Lite, Heelan Original, Blair & Minchinton	mm/s
Damage	Holmberg-Persson, Jointed Rock	Damage index
Pressure	Borehole Pressure, Powder Factor	MPa, kg/m³
Detonation	Multi-primer front propagation, Em computation	ms, kg^A
Flyrock	Richards & Moore, Lundborg, McKenzie (SDoB)	metres, m/s
Movement	Voxel-based blast throw with Rapier3D WASM physics	displacement vectors

Demo

Run the interactive demo to see all models in action:

npm run dev

Opens examples/index.html at http://localhost:5175 — vibration heatmaps, damage, pressure, flyrock, detonation, and ballistic envelope.

Quick Start

Single-point PPV

import { computePPV } from 'blast-physics-js';

const ppv = computePPV(
  { x: 100, y: 200, z: 0 },       // observation point (m)
  deckEntries,                      // array of DeckEntry objects
  { K: 1140, B: 1.6, e: 0.5 }     // site constants
);
// Returns: number (mm/s)

Grid computation

import { computeScaledHeelan } from 'blast-physics-js';

const grid = computeScaledHeelan(
  deckEntries,
  holeEntries,
  { minX: 0, minY: 0, maxX: 200, maxY: 200, cellSize: 1.0, elevation: 0 },
  { K: 1140, B: 1.6, chargeExponent: 0.5, elemsPerDeck: 12 }
);
// Returns: GridResult { data: Float32Array, rows, cols, minX, minY, cellX, cellY, unit, model }

Low-level model API

import { ScaledHeelanModel } from 'blast-physics-js';

const model = new ScaledHeelanModel({
  K: 1140, B: 1.6, chargeExponent: 0.5,
  elemsPerDeck: 20, pWaveVelocity: 4500, poissonRatio: 0.25
});

const ppv = model.evaluate(point, deckEntries, holeEntries);
const result = model.computeGrid(deckEntries, holeEntries, gridParams);

Web Worker (Blair time-domain)

import { createBlairWorker } from 'blast-physics-js/workers';

const worker = createBlairWorker();
const strip = await worker.compute({
  deckEntries, holeEntries,
  gridParams: { minX, minY, elevation },
  modelParams: { K: 700, B: 1.5, bandwidth: 10000 },
  startRow: 0, endRow: 100
});
// strip: Float32Array

Data Structures

HoleEntry

Blast hole geometry and properties. Aligned to Kirra's Blast Hole Management.

{
  entityName,                     // Blast pattern name
  holeID,                         // Unique hole identifier
  collarX, collarY, collarZ,     // Collar position (m)
  toeX, toeY, toeZ,              // Toe position (m)
  holeDiamMm,                     // Borehole diameter (mm)
  holeType,                       // 'Production', 'Presplit', 'Buffer', etc.
  benchHeight,                    // Collar Z to grade Z (m)
  subdrillLength,                 // Grade to toe along hole (m)
  holeTime,                       // Surface initiation time (ms)
}

DeckEntry

One deck within a blast hole. Aligned to Kirra's Charging System with four typed deck categories.

{
  deckType,                        // 'COUPLED' | 'DECOUPLED' | 'INERT' | 'SPACER'
  topX, topY, topZ,               // Charge top position (m)
  baseX, baseY, baseZ,            // Charge base position (m)
  mass,                            // Explosive mass (kg, 0 for INERT/SPACER)
  density,                         // Explosive density (kg/L)
  vod,                             // Velocity of detonation (m/s)
  holeDiamMm,                      // Borehole diameter (mm) — from parent hole
  chargeDiamMm,                    // Effective charge diameter (mm):
                                   //   COUPLED:   = holeDiamMm (full contact)
                                   //   DECOUPLED: = product diameter (air gap)
  timingMs,                        // Total detonation time (ms)
  holeIndex,                       // Index into HoleEntry array
  primerFraction,                  // 0.0 = top, 1.0 = base
}

Why two diameters? COUPLED explosives fill the borehole — charge diameter equals hole diameter. DECOUPLED (packaged) explosives have an air gap — the charge diameter is the product's physical diameter, which is smaller. Pressure models need the borehole wall radius; mass calculations need the charge diameter. Both are carried per-deck.

Vibration Model Hierarchy

The library provides five vibration models with increasing fidelity and computational cost:

1. PPV — Simple Site Law

PPV = K × (D / Q^e)^(-B)

Point-source evaluation at charge centroid. O(n) per point. Real-time.

2. PPV Per-Deck

Same physics, but evaluates at top/centre/base of each deck individually. Multi-deck holes show separate influence zones.

3. Scaled Heelan — Blair Non-Linear Superposition (RMS)

Blair & Minchinton (2006). Each deck subdivided into M elements with non-linear charge superposition:

Em = [m × w_e]^A − [(m−1) × w_e]^A
PPV_element = K × Em × R^(−B) × F(φ)

Heelan radiation patterns F₁(φ), F₂(φ). Viscoelastic attenuation via Qp, Qs. GPU-friendly (no time loop).

4. Blair Lite — Improved Radiation Patterns

Same RMS energy summation but with Blair's Vs/Vp-dependent radiation patterns:

sfacp = 1 − 2(Vs/Vp)² cos²φ     // P-wave: non-zero on axis
sfacs = sin(2φ)                    // SV-wave with fud=1.2 regularisation

Primer-aware element ordering. Vs derived from Vp + Poisson's ratio.

5. Blair & Minchinton — Full Time-Domain

Coherent waveform superposition with P-wave and SV-wave arrival times:

w(p) = (p^N − 2N·p^(N−1) + N(N−1)·p^(N−2)) × exp(−p)

Captures constructive/destructive interference. O(n × M × T) per point. Web Worker parallelism for grid computation.

Damage Models

Holmberg-Persson: Near-field damage index via sub-element integration. DI = peakPPV / PPV_critical.

Jointed Rock: Combined intact rock fracture (σ_d / σ_t) and Mohr-Coulomb joint failure (τ / (c + μσ_n)).

Flyrock Models

Three algorithms with increasing conservatism:

Model	Inputs	Basis
Richards & Moore (2004)	Burden, stemming, explosive density, K	Face burst + cratering + stem eject
McKenzie (2009/2022)	SDoB, hole diameter, stemming, density	Chiappetta Scaled Depth of Burial
Lundborg (1975/1981)	Hole diameter only	Empirical upper-bound envelope

3D shroud generation using the Chernigovskii ballistic envelope.

Blast Movement (Phase 5)

Physics-based blast throw prediction — an open-source approach to the problem solved by Orica's OREPro 3D Predict.

Concept: The vibration models provide the energy field (initial conditions). A WASM physics engine (Rapier3D) simulates the dynamics — voxelised rock mass with gravity, friction, collisions, and muckpile formation.

Workflow:

1. Import pre-blast surfaces from Kirra CAP file (blast block, pit shell, floor, free face)
2. Voxelise rock mass within surface bounds (~48k voxels for a typical bench)
3. Compute per-voxel initial velocities from PPV field + timing sequence
4. Simulate forward with Rapier3D WASM rigid body dynamics
5. Extract displacement vectors and predicted post-blast surface

Outputs: Displacement vectors (equivalent to OREPro 3D's SmartVectors™) for block model transformation, and predicted post-blast muckpile topography.

Package Structure

blast-physics-js/
  src/
    index.js
    core/
      ChargeColumn.js          DeckEntry.js            RadiationPattern.js
      Waveform.js              RockMass.js
    vibration/
      PPV.js                   PPVDeck.js              ScaledHeelan.js
      ScaledHeelanBlair.js     HeelanOriginal.js       BlairMinchinton.js
    damage/
      HolmbergPerssonDamage.js JointedRockDamage.js
    pressure/
      BoreholePressure.js      PowderFactor.js
    detonation/
      DetonationSimulator.js   EmComputation.js
    flyrock/
      FlyrockTrajectory.js     FlyrockShroud.js
    movement/
      VoxelGrid.js             InitialVelocityField.js
      BlastMovementSimulator.js DisplacementField.js    PostBlastSurface.js
    workers/
      BlairHeavyWorker.js      FlyrockWorker.js
  test/
  dist/

Implementation Roadmap

Phase	Version	Scope	Status
1	v0.1.0	Core data structures + PPV site law + PPV per-deck	✅ Complete
2	v0.2.0	Scaled Heelan + Blair Lite + Holmberg-Persson + Jointed Rock damage	✅ Complete
3	v0.3.0	Blair & Minchinton time-domain + Web Workers + Heelan Original	✅ Complete
4	v1.0.0	Detonation simulator + flyrock (R&M, Lundborg, McKenzie) + pressure + powder factor	✅ Complete
5	v2.0.0	Blast movement: voxelisation, Rapier3D physics, displacement vectors, post-blast surface	🔜 Planned

References

• Blair, D.P. & Minchinton, A. (1996). On the damage zone surrounding a single blasthole. Fragblast-5, Montreal.
• Blair, D.P. & Minchinton, A. (2006). Near-field blast vibration models. Fragblast-8, Santiago.
• Blair, D.P. (2008). Non-linear superposition models of blast vibration. Int. J. Rock Mech. Min. Sci. 45, 235–247.
• Blair, D.P. (2015). Wall control blasting. Fragblast 11, Sydney.
• Heelan, P.A. (1953). Radiation from a cylindrical source of finite length. Geophysics 18, 685–696.
• Holmberg, R. & Persson, P.A. (1979). Design of tunnel perimeter blasthole patterns to prevent rock damage. Tunnelling '79, London.
• Chiappetta, R.F. & Treleven, J.P. (1997). Scaled Depth of Burial concept for flyrock risk assessment.
• Richards, A.B. & Moore, A.J. (2004). Flyrock control — by chance or design. Proc. 30th ISEE Conf.
• McKenzie, C. (2009/2022). Flyrock range and fragment size prediction / validation.

Related Projects

• Kirra — Web-based blasting pattern design application for mining and construction
• trimesh-boolean — Open-mesh boolean operations for Three.js

Author

Brent Buffham

• blastingapps.com
• kirra-design.com
• Buy Me a Coffee

License

MIT © Brent Buffham 2026