Deformation of containers in the Tianjin explosion

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Discussion Overview

The discussion revolves around the deformation of shipping containers following the Tianjin explosion, specifically exploring the energy required to cause such damage. Participants examine various factors including the nature of the deformation, the effects of shock waves, and potential methods for estimating the energy involved.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that the containers appear to be melted due to heat rather than crushed by the explosion.
  • One participant notes that the shock wave from a large explosion can create significant overpressure, potentially crushing containers if the force is applied for a sufficient duration.
  • Another participant challenges the claim of "hundreds of pounds per square inch" of blast overpressure, referencing sources that suggest a more modest overpressure of around 10 psi can cause severe damage.
  • A participant proposes estimating the energy based on the size of the explosion crater, noting that energy requirements may increase with the radius of the crater.

Areas of Agreement / Disagreement

Participants express differing views on the mechanisms behind the deformation of the containers, with some emphasizing heat effects while others focus on shock wave dynamics. There is no consensus on the exact energy calculations or the nature of the damage.

Contextual Notes

Participants reference various models and sources for calculating blast effects, indicating that accurate calculations are complex and may depend on specific conditions and assumptions.

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Anders Bruun said:
The containers in the image seem to have been crushed/deformed - but how much energy would be needed to do this?

They look more melted from the heat of the fires than crushed by the explosions...
 
berkeman said:
melted from the heat of the f
Very little burnt paint.
 
The shock wave from a large explosion applies an overpressure of hundreds of pounds per square inch as it passes by. That pressure makes for an enormous force when multiplied by the surface area of a shipping container - they'd be squashed flat as a penny on a railroad track if the force were applied for more than the few milliseconds it takes the shock wave to pass by.

Calculating blast effects accurately is difficult, but Google will find some useful models that will give numbers in the right order of magnitude.
 
Nugatory said:
The shock wave from a large explosion applies an overpressure of hundreds of pounds per square inch as it passes by. That pressure makes for an enormous force when multiplied by the surface area of a shipping container - they'd be squashed flat as a penny on a railroad track if the force were applied for more than the few milliseconds it takes the shock wave to pass by.

Calculating blast effects accurately is difficult, but Google will find some useful models that will give numbers in the right order of magnitude.
I don't know about "hundreds of pounds per square inch" of blast over pressure from a shock wave, at least not after it has propagated some distance from the explosion.

According to this:

https://en.wikipedia.org/wiki/Overpressure

and

http://www.cdc.gov/niosh/docket/archive/pdfs/NIOSH-125/125-ExplosionsandRefugeChambers.pdf

a much more modest over pressure of only 10 psi can blow off limbs and will severely damage, if not demolish, reinforced concrete structures.
 
Maybe it would be possible to use the size of the crater to estimate it?

The crater from:

West Fertilizer Company explosion - Wikipedia, the free ...

was around 30 meters in diameter. The one from Tianjin is around 100 - 110 meters in diameter.

From what I understand the energy needed increases by r^5, so maybe that could be used ?
 

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