Steel bridges deteriorate over time and require regular inspection and repair. One of the most difficult areas to examine is the bridge deck, as it’s covered by ballast and track, and lifting these every time they need checking would be impractical.
FRP (Fibreglass Reinforced Plastic) ballast retention panels can be installed onto the face of the girders, so engineers can inspect what are called the Hidden Critical Elements (HCE) – the steel deck sections that get congested by ballast, grit and water.
Amco awarded TRS the contract to install FRP panels on 28 steel bridges across the South West Region.
On inspection, our biggest challenge was the volume of ballast (reaching up to 900mm in places) compacted in confined spaces, with as little as 100mm clearance from the sleeper-end to the face of the girders.
In addition, bridge spans varied from 9m to 70m and depending on how may girders there were, there could be as much as 240m of ballast retention to be excavated and re-installed on any one bridge.
With possession times at a minimum, we needed to find a fast and effective way to excavate the ballast quickly and efficiently, leaving enough time to install the FRP and its components, and get the ballast back in and fit for the passage of trains.
Following considerable research we invested in Tube Cubes – large hoovers that can suck up approx 1.2t of ballast – fast.
The Tube Cube proved very efficient and excavates on average 10m of ballast per hour at 800mm depth – a feat that could not be achieved with traditional manpower and shovels.
The Tube Cube is reducing the timescales of the programme hugely, leaving our skilled labour to install the FRP retention in record time. We also use the Tube Cube to re-instate the ballast by lowering it over the excavation and opening the hatch doors on the bottom – again saving on valuable time and labour costs.