17 January 2006

Marsh Mills Flyover

This may look like an ugly bit of concrete but it is a special bit of concrete - honest!
Its the slip road onto the Marsh Mills A38 Flyover. These are famous in civil engineering circles as they were built using a very unusual technique.

The photo below was taken in 1980 (taken from the excellent Cyberheritage)and shows what the area used to look like...

You will see the original road bridges down onto the roundabout were used as the slip roads onto the new flyover - which was built in between the two carriageways.
Just out of interest the large factory bottom left is the old Tecalamit factory which is now the site of a large retail park and Vospers Ford car and van dealership and also a Novotel. Top right is now a large Sainsburys Supermarket.

Once the new flyover had been built it was soon discovered that the original bridges were suffering from a condition known as concrete cancer so had to be demolished. The normal way of doing this would have caused major traffic congestion! So a novel approach was called for.
The new slip roads were built alongside the old ones. Traffic was then diverted onto the new slip roads while the old roads were demolished. Then over the course of a few days the slip roads were closed off and were slowly slid into the place where the old roads used to be. Excellent idea!

DYWIDAG-Systems International Limited had more detail on the work here.
TGP have a small feature on the construction here with a link to a video of the event (avi) which is well worth a look.

Here you get a better look back along the flyover looking towards Cornwall. This is taken from the pedestrian bridge over the railway which can be seen on the 1980 photo. My son Zak is looking out for trains for me.

Finally a look under the road, up the railway as it heads towards London. Tavistock Junction is just up from here. More on this later...


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