Invention pays off in Cornwall
A structural renovation of culverts on a major roads in the South-west of England has been successfully completed by Insituform Technologies.
Insituform Technologies has carried out the structural renovation of several culverts running beneath the main and heavily trafficked A30 and A38 holiday routes through Devon and Cornwall. Because of estimated future drainage flows and the load bearing capacity requirements from the increasing traffic flows on these routes, the renovation installations are required to ensure the long-term operational viability of the culverts.
The project is being carried out through the UK Highway Agency’s managing agent contractor EnterpriseMouchel. Known as the Wadham Culvert installation, the project comprised rehabilitating a 1.25m diameter, 130m long corrugated steel culvert running beneath the main A38 trunk route near Liskeard, Cornwall, and proved to be no ordinary lining project.
There were various difficulties to overcome, not least of which included the location and the total lack of useable access to the pipeline. The culvert was located at 27m below the surface of the A38 road at a point where there was no available direct access to the pipeline. This problem was solved by the construction of a new temporary roadway to connect the nearest access point from the A38 to the construction site.
The roadway had difficulties as well in that the only available route required the road to be built with a 2:1 gradient to create the required access to the work site as well as provide major clearance of the thickly overgrown vegetation along the proposed route. With site access finally possible, work commenced for the installation of a new iPlus liner.
More clearance work at the launch site was required to correctly position all the necessary site equipment so that the lining work could proceed unhindered. The liner, manufactured in the US and resin impregnated by Insituform, was transported to the jobsite in a refrigerated truck timed to arrive so that a temporary overnight road closure could be placed on the A38 to allow off-loading of the liner for final transport to the installation site.
This timing was necessary because attempting any road closure during heavily trafficked daylight hours would have been out of the question and off-loading the liner would have simply been unsafe without the road closure. On arrival, the liner was transferred to a tractor/trailer which carried the liner down the very steep, temporary roadway to the culvert site.
It was planned to install the iPlus liner using air inversion techniques and steam curing. Given the location, access difficulties and the available working area, it was felt that this was the only practical solution because the logistics of water delivery for a hot water cure would have simply added to the site’s operational problems.
To achieve the installation, a scaffold was erected at the launch end of the culvert with the air inversion unit sited to allow easy installation of the liner into the culvert. To ensure the liner passed into the culvert without difficulty and to support the liner during the installation process, a conveyor was used between the tractor trailer and the scaffold to feed the liner into the air inversion unit.
Once the liner was in position, the steam generator was attached to the liner and then the liner was inflated using air. Finally, steam was passed through the liner to compete the cure process.
John Beech, Insituform business development manager, says: “This was certainly no easy project. The major access difficulties, steep temporary roadway down to the deep set launch site and heavy traffic on the A38 trunk road meant that we had to be very inventive to bring the works to a successful conclusion.”
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