Turning the world upside down
A technique used by the Romans
Cross section of a route
Materials and tools
- A 360 degree tracked excavator. Machine size varies with each location. On open ground with no containment problems, a 12 to 15 tonne machine is preferable. On steeper slopes or in tighter locations, 5 to 7 tonnes is more suitable. If access demands, or across very steep side gradients, a 3 tonne machine can still produce good results.
- Suitable sub soil for route construction. Typically this will be glacial drift which underlies much of the peat particularly in the North and West of the UK.
- Seed - approved by an ecologist.
- Drainage materials if required, such as culvert pipes.
Construction
- Remove overlying turfs carefully and place to the side for reuse in the construction. Once work is underway, use these as soon as possible to revegetate the area immediately behind the digger so they are only handled once.
- Excavate the ditch to sufficient depth to reach the sub soil and obtain enough material for route construction. Excavate materials from the upside of the route, or on both sides.
- Install any additional drainage required, such as fords across or culverts under the route.
- Excavate the subsoil and deposit this on the vegetation layer along the route, to at least 600 mm thickness above the original ground level.
- Place any excavated aggregate so that the coarser material is near the base of the route construction and the finer material at the top.
- Compact the placed material with the excavator bucket and form a camber or crossfall on the route surface.
- Replace any excavated material unsuitable for route construction within the adjacent ditch.
- Ensure the ditch has a smooth base with a slight fall (gradient) to prevent standing water or stagnation.
- Replace turfs over the surface of the ditch and the shoulders of route.
The finished track will settle down by up to 300mm - 450mm over the next couple of years.
