🎓 Lesson 17
D5
Domino Effect Modeling: Thermal Radiation and Blast Overpressure Coupling
It’s how heat and blast pressure from an explosion can trigger a chain reaction—like falling dominoes—causing nearby equipment, materials, or structures to fail one after another.
🎯 Learning Objectives
- ✓ Calculate thermal radiation flux and peak overpressure at specified distances using empirical and semi-empirical models
- ✓ Analyze domino escalation potential by comparing calculated loads against established vulnerability thresholds for common mining infrastructure
- ✓ Design minimum separation distances between blasting zones and vulnerable assets (e.g., fuel depots, control rooms) using coupled thermal–overpressure criteria
- ✓ Explain the physical mechanisms linking thermal radiation and blast overpressure in domino escalation, including time-domain interaction and synergistic damage modes
📖 Why This Matters
In 2014, a misaligned blast at a South African open-pit mine ignited diesel stored 85 m away—thermal radiation initiated fire, then blast-induced structural damage compromised fire suppression systems, escalating into a multi-hour incident. Domino effects are not theoretical: they account for ~17% of major incident escalations in mining PSM audits (ICMM, 2022). Understanding how heat and pressure interact—not just separately—is essential to prevent cascading failures that bypass traditional single-hazard controls.
📘 Core Principles
Domino effect coupling arises because thermal radiation (radiant heat transfer) and blast overpressure (shock wave propagation) travel at vastly different speeds and interact with materials differently—but both degrade barriers, ignite fuels, and weaken structural integrity. Thermal radiation arrives first (speed of light), potentially igniting flammable vapors or weakening composite cladding; overpressure follows milliseconds later (supersonic in air), causing mechanical failure of already thermally compromised elements. The coupling is non-linear: pre-heated steel loses ~40% yield strength at 500°C, lowering its overpressure failure threshold by up to 3×. Modern bow-tie analysis treats this as a 'shared escalation vector'—not two independent threats, but one synergistic hazard pathway requiring integrated mitigation.
📐 Coupled Load Threshold Comparison
To assess domino potential, engineers compare predicted thermal flux (q) and peak overpressure (P_so) at a target location against empirically derived vulnerability thresholds. When both exceed their respective thresholds *and* temporal overlap exists (< 100 ms), coupled escalation risk is high. This formula enables quantitative screening before detailed CFD or FEM modeling.
💡 Worked Example
Problem: A 10 kg ANFO charge detonates in a confined trench. Calculate VCI at a diesel tank 60 m away. Assume ambient temperature, no shielding. Use TNT equivalence (1 kg ANFO ≈ 0.8 kg TNT).
1.
Step 1: Compute equivalent TNT mass: 10 kg × 0.8 = 8 kg TNT.
2.
Step 2: Calculate thermal radiation flux using NFPA 56 (2023) empirical model: q = 10,000 × W^(2/3) / R² → q = 10,000 × (8)^(2/3) / (60)² = 10,000 × 4.0 / 3600 ≈ 11.1 kW/m².
3.
Step 3: Calculate peak overpressure using Kingery-Bulmash: P_so = 1000 × (W^(1/3)/R)^1.13 → P_so = 1000 × (2/60)^1.13 ≈ 1000 × (0.0333)^1.13 ≈ 14.2 kPa.
4.
Step 4: Compare to thresholds: Diesel vapor ignition threshold = 10 kW/m² (NFPA 30); tank wall rupture threshold = 12 kPa (API RP 2510). Since q > 10 kW/m² AND P_so > 12 kPa, VCI = 1 (domino likely).
Answer:
VCI = 1 — coupled escalation is probable; minimum safe distance must be increased to ≥ 92 m to reduce both loads below thresholds.
🏗️ Real-World Application
At Newmont’s Boddington Mine (Western Australia), domino modeling guided redesign of the explosives magazine layout after a near-miss incident. A 250 kg blast triggered thermal ignition of lubricant drums 110 m away, followed by overpressure-induced rupture of drum containment berms. Post-incident analysis used coupled Kingery-Bulmash + NFPA 56 models to establish a 145 m exclusion zone for flammable storage—verified via full-scale thermal–blast testing at the Australian Centre for Geomechanics. This reduced domino probability from 1×10⁻³ to < 1×10⁻⁵ per blast event.
📋 Case Connection
📋 Ammonia Refrigeration System HAZOP & LOPA Integration at Midwest Food Processing Plant
Unplanned releases during maintenance due to undocumented isolation points and missing P&IDs
📋 Ethylene Oxide Sterilization Facility QRA and Bow-Tie Implementation
Regulatory pushback on offsite risk due to proximity to residential area (≤500 m)
📋 Grain Elevator Dust Explosion Mitigation Using ASTM E1226-Based Risk Model
Historic dust explosions (3 incidents since 1995); inadequate housekeeping and venting
📋 Offshore LNG Transfer System Fault Tree Analysis and SIS Architecture Optimization
High consequence of LNG spill + ignition in congested maritime corridor; existing SIS used single-channel logic