Tunnel explosion characteristic - istss

Tunnel Explosion Characteristics
Rickard Forsén
FOI Swedish Defence Research Agency
Defence and Security Systems and Technology, Tumba, Sweden
Introduction
Examples of applications
Characteristics ot tunnel explosions
Possible risk reduction measures

Introduction
Explosion characteristics:
Sudden increase in volume and release of energy
Creating:
High pressure/shockwave
Usually generation of:
High temperature
Release of gases
May result in:
High velocity fragments

Introduction
Example of consequences of tunnel explosions:
Local effects:
Extremely high pressure
Cratering, spalling, punching, debris throw
Damage to structures above tunnel covering
Distant effects inside tunnel:
Damage to separating/dividing structures, vehicles, humans
Outside adits:
Jets
Heat from fire ball

Introduction
Example of scenarios:
Dangerous goods accidents with:
Hazard division 1 – high explosive substances and products
Hazard division 2 – inflammable gases
Hazard division 5 - oxidizing agents
Antagonistic acts of explosion
Briefcase/suitcase bombs
Car bombs (sedans .. vans .. trucks)

Examples of application
Shock tubes: - experimental arrangement for well defined testing
1.6 m
1.5 m
2
1
3
10 m
4

Examples of application
Fortifications
Blast propagation
in tunnel systems

Underground Ammunition Storage
Examples of application
Scale 1:3
Debris
Chamber
Traps
30 x 9 x 4 m
Main Tunnel
Main
Tunnel
100 x 15 m 2
Access Tunnel
Access
170 x 8 m 2 Tunnel
Debris
Trap
Slot
Tunnel
Detonation
Chamber
Old Klotz Tunnel
Entrance
Portal
Barricade
TEST FACILITY LAYOUT

Examples of application
Underground
Ammunition
Storage
Test with
10 tons of
high explosive
Test 4b

Examples of application
At tunnel exits:
A long-duration jet and
a short-duration shock wave

Examples of application
Calculations with AUTODYN - Jet hitting simulated
building 100 m in front of adit
10 ton 40 ton

Characteristics
250 m tunnel length, 4 m 2 tunnel area, 50 kg HE

Examples of application
Buildings above tunnels with
dangerous goods transports

Antagonistic threats
Examples of application

Overpressure (kPa)
Characteristics
High explosives detonations in tunnels:
considerably higher pressure
considerably longer duration
10000
1000
16 000 kg in 50 m2 tunnel
100
400 kg in 50 m2 tunnel
400 kg in free air, surface burst
10
1
10 100 1000 10000 100000
Stand off (m)
16 000 kg in free air, surface burst
Parameters of the
tunnel affecting the
pressure attenuation
are:
- Length of tunnel
and standoff from
explosion to target
- Cross section area
of the tunnel
- Roughness/friction
of the walls
- Turns of tunnel
direction and area
changes etc.

Characteristics
Gas explosions in tunnels:
High burning velocities due to confinement and turbulence

Possible countermeasures
1. Exclude high explosives and other potentially
exploding substances from tunnels
Certain dangerous goods transports forbidden entirely or
allowed only on limited occasions - disadvantages in that
the risks for the alternate routes may be higher to the
society as a whole.
Detection of, for example, high explosives (antagonistic
threats) - difficult challenges are fast detection and at
significant standoff distances

Possible countermeasures
2. Automated systems with blast energy absorbers
(for example water mist) initiated with sensors to
detect an explosion
Lack of reliability of blast identification
Low speed of blast energy absorber activation
Inadequate discharge of blast absorbing agent.

Possible countermeasures
3. Design of structures inside the tunnel and at the
adits, and above the tunnel to resist the load from
explosions.
The most robust method of preventing unacceptable damage

Thank you, questions?