OT - impressive bit of civil engineering - update

Dec 27, 2025 Last reply: 6 months ago 36 Replies

I posted here 6 weeks or so ago about a new underpass being planned for J10 of the M27.



The motorway was closed at 2000 on Christmas Eve, the road surface removed by 0300 on Christmas Day, and the 24000m^3 of soil where the underpass will go was excavated by early afternoon Boxing Day. Info at

formatting link
. Not long after that the 8500 ton underpass was slid into position. Video here:
formatting link



It doesn't mention it on the above page, but evidently the "lubricant" used to help the underpass slide was a bentonite slurry.


In message <10iokll$39ee9$ snipped-for-privacy@dont-email.me, Jeff Layman snipped-for-privacy@invalid.invalid writes

Thanks for posting that, I was hoping someone would do a time lapse on it.

What isn't obvious (to me anyway) is how they were moving it, were they pulling it along, or pushing it ?.

Adrian

Nice to see intelligent engineering has not been totally wiped out by vapourware

Invisible unicorns. Its the latest thing.

Same question from me, the units at the edge seemed a bit small to move that!

Thanks for the link :-)

Pushing. According to

formatting link
(about halfway down) "Together, these jacks will exert an enormous pressure, roughly equivalent to the combined weight of 595 elephants pushing at once."

Also

formatting link
:"Test push successful".

a bit of both, the green machines were gripping onto the 'bundles' of steel rope passing through them, and repeatedly inching along them

More obvious on their first test move

formatting link

Here's one from this year, near Coventry to take the A46 over HS2

formatting link

In message <10ions0$39ee9$ snipped-for-privacy@dont-email.me, at 13:44:32 on Sat, 27 Dec

2025, Jeff Layman snipped-for-privacy@invalid.invalid remarked:

That's very precise. So more than 590 elephants, but less than 600?

And are these baby elephants, or grown up ones.

You could use this older vid as a example.

"HS2 completes UK’s heaviest bridge slide"

formatting link
It has a bit of time lapse sprinkled through it.

Maybe the video of this project will be available later, complete with the time lapse.

Paul

There was one person responsible for ensuring this happened properly and on time, what a responsibility!

Pink ones, Roland.

I think that the "pull" jacks were there to keep the concrete structure moving straight ahead, as pushing alone often results in the object not moving where you want it to go (shed trolleys!...).

Does anyone know the reason why the new underpass is necessary?

Will a road be routed through it?

Hampshire County Council claim they know. (Google their website)

More likely than a railway or a river.

In message snipped-for-privacy@mid.individual.net>, JNugent snipped-for-privacy@mail.com writes

The new underpass is adjacent to junction 10, which has very restricted access (M27 westbound to A32 Northbound and vice versa only). The junction is being upgraded to allow entry/exit in all directions, so the underpass will take traffic to/from the westbound lane of the M27.

Adrian

Of course. Silly me for not realising ;-)

Adrian

In message <10ions0$39ee9$ snipped-for-privacy@dont-email.me, Jeff Layman snipped-for-privacy@invalid.invalid writes

Thanks.

Adrian

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required