I was looking forward to seeing some german bunds, but it looks like they were pretty confident in their ability to remove the fuses. Not the first bombs these gents have seen!

In this position they'll have better access and more space to build protective structures around the bombs in case they do detonate - similar to the Great Yarmouth bomb in 2023. bsky.app/profile/andr...

Pictures indicate that the bombs have been found in a more open area by the river, which would would factor into the EOD team's decision to attempt to defuse the bombs in place.

This has obviously had tragic consequences for the crew of the Cuauhtémoc, but avoided additional casualties amongst the bridge users.

The bow of the Dali directly struck one of the main piers of the Key Bridge – the energy of that collision was huge. In comparison, masts are relatively weak and flexible, and so break easily in a collision with a stiff bridge deck.

I've had an empty account sitting here for ages, but finally had enough of the other place. Glad to see there's some interesting folk in the room already. :)

The tools used by government agencies like Dstl to plan these EOD operations rely on research on the behaviour of soils under very rapid loading, prediction of blast waves in urban environments, and the effects of ground shock. These are all things I'm involved in researching - follow for more info!

Even though the EOD team was unable to disarm the bomb without detonation on site, the mitigation measures seem to have worked perfectly, without any injuries or serious damage caused. All thanks to sand (and a lot of clever people). 👏

In the video you can see that the sheet piles themselves become projectiles, but mostly fall back within the area of the enclosure. The scaffolding struck by a pile will need repair, a few car windows are broken, and there's some damage to the river wall.

The sheet piles that formed supported the sand on the enclosure roof are perforated with holes from the bomb casing fragments. These fragments were then captured by the sand in the walls and roof - no fragment damage has been reported.

The blast is channelled upwards through the sand on top of the enclosure, resulting in the jets of sand visible in this image. Kinetic energy in the sand is kinetic energy that isn't available to the air shock, so full marks there. What about fragments?

An attempt was then made to destroy the explosive by controlled burning, which is riskier as there is a chance of a transition to detonation. This did indeed happen, but luckily we have drone footage to see the sand enclosure in action! 💥

Once the protective structure was in place the work to deactivate the bomb could begin. An initial plan to cut into the bomb and render it safe to transport had to be abandoned, after water used in the cutting process threatened the stability of the sand walls.

As an explosion would also result in a shock transmitted into the ground, nearby buried utilities were also taken into account, such as the presence of gas mains. The EOD team, Dstl, local authorities and utility providers will have all worked together to finalise a solution.

The design of the enclosure will vary depending on factors such as the type of explosive device and the proximity of other structures: in this case it looks like an extra L-shaped wall has been added to protect nearby houses.

Hesco MIL units are like a conventional gabion steel mesh, but lined with a geotextile material that allows them to be filled with finer soils like sand. Machinery can be used to do all the heavy lifting, then some compaction by foot and you're done.
So easy even I can do it...

Instead, the EOD team made use of Hesco MIL units and excavators to rapidly build a hefty sand enclosure around the bomb, with more sand on the roof supported by steel sheet piles.