01.07.08
Croxley to Watford embankment stabilisation
Source: Rail Technology Magazine June/July 2008
Clancy Docwra Rail Division was recently awarded a scheme by Metronet to stabilise a 430m section of embankment between Croxley and Watford on the Metropolitan Line.
The scope consisted of the removal of vegetation, driving 420 steel piles to the rear of the line’s cable runs, the placement of concrete planks between the piles, finally levelling the void between the planks and the track creating a new CESS.
The client’s proposal was for the works to be undertaken using specialist road/rail plant during an extended weekend possession. Although tendered and awarded on this basis, Clancy Docwra identified opportunities for improving the proposal which were pursued with the client through a joint engineering workshop.
A site trial prior to the main possession was organised. Twenty piles were installed which, whilst confirming the viability of the scheme, also identified improvements such as a move from hammer to vibration piling and a review of material logistics which was agreed and implemented.
Advance works included:
• Removal of vegetation and installation of a scaffold walk-way to enable safe working access.
• Manufacture of specially designed pile frames to facilitate accurate locationing of 5-pile sections.
• Materials delivery and preparation of a road/rail transfer programme.
The Bank Holiday weekend 72-hour possession was a total success, despite continual heavy rain, and featured:
• 100m of Type 1 footpath laid to give safe site access
• Utilisation of 6 of road /rail units.
• Road closure on a bridge over the works to enable loading of materials by crane.
• The plan was to install piles and planking concurrently. However, due to the weather, a decision to drive all piles in first was made, and succeeeded in completing most of the 400 required (up to 4.5m deep).
• 80% of the planking was installed.
• Piling also included dealing with the restrictions associated with bridge foundations and trackside plant. These were installed during a second possession together with outstanding planking and CESS works.
• 430m of hand rail was installed to the top of the new structure during traffic hours.
Tell us what you think – have your say below, or email us directly at [email protected]