CLIENT: Network Rail

PROJECT DURATION: 52 Hour Possession

BUDGET: Within budget

The Problem: 
Network Rail had a water ingress problem within a pre-cast concrete segmental tunnel. The water was mainly entering through concentric, co-axial circle joints between rings.

In this particular tunnel the tracks were mounted directly on the concrete base slab and the volume of water was sufficient to bridge the gap between running rails. This was leading to signalling problems outside the tunnel.

Several ineffective methods to deal with the ingress over the tracks had already been used. These included caulking to joints and then installing plastic drip trays, but the volume of water was too high for this to be effective and simply moved the problem somewhere else in the tunnel.

The Solution:
The H2Ox Engineers took into account the need for flexibility to take up the thermal, cyclical and vibration movements encountered in a rail tunnel. They decided on a system of resin injection within the leaking joints, using a single component polyurethane resin, which cured to hydrophobic flexible foam.

A 52 hour weekend possession was set aside for a trial and Network Rail selected some of the most problematical joints to thoroughly test the new system on.

The H2Ox team worked around the clock to fix the problem within the deadline, with four Injection Crews rotated in 12 hour shifts. Within 44 hours, 12 joints were successfully sealed providing a permanent solution with no need for the drip trays - all within the overall works budget.