Delta have provided Koster, an elastic, permanent repair solution for the London Underground Tunnel between Kings Cross and Farringdon stations.

One area which was showing significant signs of water seepage was the tunnel`s crown, evident through old injection packet holes and badly pointed brickwork.

These areas were initially sealed using Koster Waterstop and KD2 Blitz, both products immediately prevented the passage of pressurised water.

Delta then had measure and mark out the borehole positions for Koster Superpackers. Koster Superpackers, which are small injection lances that have been specially designed to give a superior grip (within the boreholes) whilst delivering a constant flow of grouting resin.

It was specified the Injection ports to be placed at 400mm centres in a grid pattern, with a single packer positioned in the centre.

The boreholes were drilled to a predetermined depth which would facilitate the packers. Koster Superpackers were then inserted and the area was ready for the gel injection.

Koster G4 Gel is an acrylic based resin which has a similar initial viscosity to water, the Koster G4 Injection Gel fills the same minute tracks and veins that water follows when infiltrating the structure. When injected into pore structures, the Injection Gel G4 cures to form an elastic, permanent gel which is able to move and flex within the brickwork.

The G4 Injection Gel filled the full build-up of the brickwork lining (becoming part of the structure), protecting from future water ingress and its resulting damage.

The G4 Injection pump was set up and operated from a rolling platform below the scaffold tower, allowing for ease of access to each packer during the injection s tage. Following the injection phase, the Koster Superpackers were removed and the boreholes filled using Koster KB Fix 5 fastset mortar.

Within 15 minutes of the Koster G4 Gel being injected all water seepage from the brickwork slowed and ceased.

The water seepage stopping meant that the resin had “gelled” within the tunnel lining and sealed off all routes which had previously been allowing the passage of water.