Bridge collapse on M20

Author
Discussion

don'tbesilly

13,900 posts

162 months

Sunday 28th August 2016
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saaby93 said:

CAPP0 said:
Here's the "before" shot. As I said above, the path on the bridge has quite a fair gradient on it. There's a bit of an optical illusion going on, the underside of the bridge slopes less so, but it does look low at the (alleged) point of impact, if the truck with the digger was travelling on the shelf for any reason.
look at the fence line and the height of the gantry above it and the height of the bridge above the fence
Thee bridge is a good metre or more lower. Those fence panels are what 2.4metres?
I'd agree with your point Saaby, the distance between the ground and the underside of the pedestrian bridge on the hard shoulder does look very low, and I wonder if it's at the right height to comply with the regs as they are today.

If you zoom in on that point of the M20 on google maps it's even more apparent.

https://www.google.co.uk/maps/@51.3088178,0.379558...

Digga

40,206 posts

282 months

Sunday 28th August 2016
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General Price said:
It looks like the dumper hit it and got pushed back into the digger.

This looks pretty conclusive to me from the aerial POV. They sometimes leave the dumper bodies tipped to stop it filling with water. Clearly, they hadn't checked heights.

Will not take long for a couple of decent size excavators with crushers to reduce the whole thing to aggregate and load it away.



Lengthier job will be assessing the structural integrity of the other bit of the bridge.

Edited by Digga on Sunday 28th August 09:20

don'tbesilly

13,900 posts

162 months

Sunday 28th August 2016
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Just heard on the BBC that the Highways Agency are stating that they are reasonably confident that the M20 will reopen by lunchtime today, which is approx 24 hrs after the collapse.

That's remarkably quick given that it took 5 hours to remove a broken down car on the M25 the other week!

Super Slo Mo

5,368 posts

197 months

Sunday 28th August 2016
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Digga said:
This looks pretty conclusive to me from the aerial POV. They sometimes leave the dumper bodies tipped to stop it filling with water. Clearly, they hadn't checked heights.
I'm not sure I agree with that, it's a small dumper, there's no way the bucket is 4 metres plus in height when tipped.
If anything, it's the boom that's hit the bridge then the second truck hitting it as it fell has moved the bridge forwards and it's landed on the dumper.

It's interesting, if not surprising, that the second truck has stopped in about it's own length, which is quite severe deceleration. The driver probably has a few aches this morning from his seatbelt.

don'tbesilly

13,900 posts

162 months

Sunday 28th August 2016
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Super Slo Mo said:
It's interesting, if not surprising, that the second truck has stopped in about it's own length, which is quite severe deceleration. The driver probably has a few aches this morning from his seatbelt.
Getting poleaxed by a lump of steel reinforced concrete tends to bring most things to a juddering halt! biggrin

I'd imagine the driver is counting his blessings right now, and the aches he's feeling he's grateful to be able to feel.

FlyingMeeces

9,932 posts

210 months

Sunday 28th August 2016
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don'tbesilly said:
Getting poleaxed by a lump of steel reinforced concrete tends to bring most things to a juddering halt! biggrin

I'd imagine the driver is counting his blessings right now, and the aches he's feeling he's grateful to be able to feel.
That'll be the fella who needed treatment for shock!

Remarkable that nobody suffered permanent harm from this. Hope they work out for sure what did happen soon.


cahami

1,248 posts

205 months

Sunday 28th August 2016
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As pointed out by someone earlier the bucket appears to be back to front is this normal? And would it prevent the arm going right down? Also in the picture above there appears to be no chains/ straps on the front of the digger?

Edited by cahami on Sunday 28th August 10:09

carlpea

381 posts

138 months

Sunday 28th August 2016
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Live feed from CCTV on what's going on.

http://www.motorwaycameras.co.uk/viewcamera/?motor...

SilverSpur

20,911 posts

246 months

Sunday 28th August 2016
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Clearly this photo shows the front of the digger has hit something.... Remarkable that it's enough to bring down the bridge in itself.....

However, there is evidence of works also taking place on the bridge, what are the details of that? Was it being repaired, was someone already aware that it was in a bad state of repair?


SilverSpur

20,911 posts

246 months

Sunday 28th August 2016
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Just another thought.... It might be substantially harder to remove the standing part of the bridge than the bit that's actually fallen down !,,

Sheepshanks

32,530 posts

118 months

Sunday 28th August 2016
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General Price said:
It looks like the dumper hit it and got pushed back into the digger.

..and there's a bit of something the same colour as the dumper truck that is still forward of the bridge so it's pretty obvious it was that that hit the bridge. Must have been going very slowly though - the digger hasn't moved.

Digga

40,206 posts

282 months

Sunday 28th August 2016
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SilverSpur said:
Clearly this photo shows the front of the digger has hit something.... Remarkable that it's enough to bring down the bridge in itself.....

However, there is evidence of works also taking place on the bridge, what are the details of that? Was it being repaired, was someone already aware that it was in a bad state of repair?

I'd guess that was a secondary impact. If the dumper was up in the swan neck of the trailer, before it hit the bridge, that might explain the height differential.

Also, Hitachi not a Doosan as I'd first assumed.

vikingaero

10,256 posts

168 months

Sunday 28th August 2016
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I think this picture gives a good perspective of the incident:



Look at the rear doors of the white trailer for reference height and look at the height of the jib in relation to the concrete structure. The low loader may be low but there may be several models of the excavator ranging from small to large. If the Auto Renovations is contracted to move the plant then maybe they used an agency driver with little experience?

Elysium

13,756 posts

186 months

Sunday 28th August 2016
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Nickyboy said:
A few points that others have mentioned

Normal UK motorway bridge height is 5.1m.
Height limit applies to hard shoulders as well as main carraigeway, hard shoulders can be less but must be signed.
The artic crushed by the bridge is Polish registered so will be no more than 4m high




This pic shows the digger arm as nowhere near high enough to hit the bridge, it's also on one of the lowest trailers available, designed for carrying double deckers. The digger arm "could" however have been higher, knocked the bridge and the dumper truck also on the trailer being pushed back into the digger arm/bucket, thus bringing down the height of the arm. White markings on the tip of the arm would suggest it has hit the bridge so may make this feasible.

Why it was on the hard shoulder is a wonder though, it certainly wasn't travelling at speed otherwise the digger would have been wrecked or ripped off the trailer.
Bridge heights are one of those things that you imagine must be heavily regulated, but in reality are not clear cut.

I think the current standard for a new motorway bridge is 5.3m high. Existing ones can be lower.

Anything below 4.95m (16'3") should be signed. These do exist on some motorways. For example on the A58(M):

https://www.google.co.uk/maps/@53.8013585,-1.55473...

The driver got past the gantry OK, which looks new and is probably at 5.3m. The bridge is lower and the lowest point is on the hard shoulder. It looks to me as if the digger arm was unfortunately at exactly the right height to lever the bridge forward. Any higher, or if the speed was greater and the arm would probably have been ripped off. As it stands, my guess is that it tipped the bridge forward, which then fell onto the white lorry and was dragged forward of the point of impact.

If the front of the boom scraped under the bridge, it would be dragged backward, pushing the bucket into the tipper. That would form a fairly rigid triangular structure, which could have lifted the bridge slightly up and forward to the point that it fell under it's own weight. The scratches on the arm and the position of the tipper and bucket seem to fit?

Edited by Elysium on Sunday 28th August 11:20

Digga

40,206 posts

282 months

Sunday 28th August 2016
quotequote all
vikingaero said:
If the Auto Renovations is contracted to move the plant then maybe they used an agency driver with little experience?
Since the myopic, bureaucratic introduction of the driver Z PC in the UK, lack if experience is endemic. IMHO.

Elysium

13,756 posts

186 months

Sunday 28th August 2016
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SilverSpur said:
However, there is evidence of works also taking place on the bridge, what are the details of that? Was it being repaired, was someone already aware that it was in a bad state of repair?
There are temporary handrails on the bridge, which are on the streetview images from a year ago.

Looks as if the original handrails may have been unsafe, possible due to concrete blowing around the steel supports.

vikingaero

10,256 posts

168 months

Sunday 28th August 2016
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I think what has happened is bad loading from an (in)experienced driver:

(1) The digger is correctly seated over the rear wheels of the trailer for weight distribution.
(2) The digger is seated against a back stop.
(3) The jib has not been lowered enough possibly because the bucket should have been removed and lashed separately.
(4) The dumper is wedged against the knuckle of the bucket to prevent movement. This seems to be the achilles as the jib is too high. The jib cannot be lowered to wedge the dumper as the hydraulic pipes and pistons would impact against the dumper.
(5) The jib has impacted the bridge possibly at some speed and pushed the concrete bridge section forwards past the dumper.

I don't think there is a maintenance issue with the bridge. The works were to simply raise the parapets and stop stupid kids from throwing things onto the motorway:

http://www.bbc.co.uk/news/uk-england-kent-17194266
http://www.bbc.co.uk/news/uk-england-kent-33282754
http://www.kentonline.co.uk/malling/news/warning-a...
http://www.pistonheads.com/gassing/topic.asp?h=0&a...

All that jazz

7,632 posts

145 months

Sunday 28th August 2016
quotequote all
vikingaero said:
I think this picture gives a good perspective of the incident:



Look at the rear doors of the white trailer for reference height and look at the height of the jib in relation to the concrete structure. The low loader may be low but there may be several models of the excavator ranging from small to large. If the Auto Renovations is contracted to move the plant then maybe they used an agency driver with little experience?
I used to do plant delivery work albeit with larger stuff than that. The jibs on diggers are often a problem when you have other stuff on the back (especially if there are extra buckets to collect, which 9/10 times there are) because you can't tuck it away properly so that it's low enough to clear bridges as the machine(s) loaded in front of get in the way. The standard practice in that situation is to turn the digger round and have the jib hanging out the back between the beaver tails (ramps) on a traditional style plant trailer. This is what I'd have done with the load and it's also what the should've done too (drop buckets behind machine in front, then spin round, reverse up as tight as you can and fold arm away) :

https://www.flickr.com/photos/36618304@N05/1422751...

That set up enables you to tuck the job right down and fold back up on itself so that your overall ride height is as low as possible as you often need to use roads off the beaten track where you come across low bridges.

The dumper on the swan neck has nothing to do with the bridge strike. Those are plenty low enough in height to not cause any issues. It's definitely the jib arm on the duck that's punted the bridge off its mountings imho.

cossy400

3,153 posts

183 months

Sunday 28th August 2016
quotequote all
vikingaero said:
I think this picture gives a good perspective of the incident:



Look at the rear doors of the white trailer for reference height and look at the height of the jib in relation to the concrete structure. The low loader may be low but there may be several models of the excavator ranging from small to large. If the Auto Renovations is contracted to move the plant then maybe they used an agency driver with little experience?
Very good angle of pic there, does look boarder line with the other side of the bridge, but hes only just past that bit, surely if the arm had pushed it off it would be further on?


Trailer heights are all over the place, that box trailer could be 4 metres, and if so that still leaves over a metre, which looking at the pic id say is possible??

Sheepshanks

32,530 posts

118 months

Sunday 28th August 2016
quotequote all
vikingaero said:
(5) The jib has impacted the bridge possibly at some speed and pushed the concrete bridge section forwards past the dumper.
The rest of what you said seems plausible, but there surely can't have been much speed involved - the digger appears not to have moved on the trailer.

However it's then a bit odd that the dumper has twisted slightly and from the aerial shots something seems to have come off the dumper and gone forwards.