"The Lagoon" Chorleywood to Chalfont & Latimer

Well that's how I ended up taking that photo as I was asked to investigate and report on any work needed! ;D

I think I know the embankment stabilisation project you're talking about which was completed recently. I can't say alot about it but I visited the works a year ago as I knew an engineer working there. The site office compound was under the M25 flyover.

Skanska were the contractors and an earthwork berm was being constructed along the embankment to allow access for construction vehicles. I seem to remember the basic design was a concrete retaining wall built on piled foundations (there are alot of restrictions on piling work close to the railway) close to the toe of the embankment to be backfilled later on. There was a survey team checking the track for movements everyday whilst work was taking place. The decision to do this work would've been beccuase of some kind of movement of the embankment happening resulting in a temporary speed restriction in that area.

You're right. I'd expect some kind of drainage to be installed.

Yes that's the basic idea. Not much of a mud mover (geotechnical engineer) myself but going by past examples the sloped embankment is levelled up the top of the wall. Add handrails and you have a nice wide cess for track walkers.

I suppose depending on the situation other solutions can be applied such as regrading the slope and supporting the toe with a low level gabion wall. Another method is "soil nailing" where a number of angled cores are sunk into the slope and steel rods are inserted in, grouted up, then tensioned up to a predetermined level and bolted against a top bearing plate.

Depending on the line, taking into account its history and geograpical area, embankment and cuttings can be predominantly clay, chalk or ash. Its quite common for track to be laid ash waste product from power stations. These are now causing problems due to compaction during construction. It's good practice to keep well managed vegetation on embankments, especially for clay type soils which shrink or swell depending on the season. It may sound daft but over cutting vegetation like trees can leave a build up of soil water pressure without uptake from roots.

This technique is called pinning and is sometimes done to brick arch tunnels. The sub-surface tunnels are made up of up to 7 brick rings constructed on one another but sometimes voids can form to seperate the rings. This can be caused by water seepage and the arch loses some of its strength. So pinning is an option. The tunnel wall on he eastbound (i think) circle platform at Kings Cross has some work done to it.




My local station Stanmore is. Without knowing Tube Lines' plans I fell for the station publicity on building a third platform to reduce passenger waiting time...



I believe embankment stabilisation has been completed at West Ken which would've entailed some amount of vegetation clearance as enabling works. I did hear a story about some overzealous logging on the Richmond Branch a few years back. Apparently some angry letters were written to LUL by a local MP whose back garden view had been rearranged.