Metronet Rail: Embankment Stabilisation
Client: Metronet Rail
Project: Croxley to Watford Embankment Stablisation
Value: £650k
Start: April 2008
Completion: April 2008
Scope:
This scheme was awarded by Metronet Rail to stabilize a 430 metre section of embankment on the Metropolitan Line between Croxley and Watford, during two weekend possessions.
The scope included for the removal of vegetation, driving 430 steel piles to the rear of the cable run, the placement of concrete planks between piles, and finally leveling the void between the planks and the track sleepers to form a new Safe Access. (CESS)
Following award an engineering workshop revealed opportunities to improve the scheme which were tested during a pre possession trial in which 20 piles were installed. This verified the viability of the scheme and identified improvements such as a move from hammer to vibration piling, and a review of material logistics which were agreed and implemented.
Advance works included vegetation removal, advance material placement, construction of 100 metres of Type1 access foot path and the installation of a scaffold access walkway. Specially designed piling frames were manufactured to enable accurate location of 5 pile sections.
The main 72 hr possession was subject to continual heavy rain however works progressed well utilising 6 Road/ Rail Units. The plan was to install piles and planks concurrently however a decision was taken due to weather conditions to drive all the piles first with over 400 installed (up to 4.5m deep). Piling progress was so good that placement of 80%of the planking was also achieved.
The following weekend possession saw the completion of one off “special piles” around trackside plant and bridge foundation, and the installation of the remaining planks. The void between the new retaining wall and the track was then in filled creating a new CESS
Both possession works were completed on time and the railway handed back to the client, progress was such that a third reserve possession for the next weekend was not required.
Remaining works were carried out in traffic hours including the installation of 430metres of hand rail to the top of the piled structure, and the removal of the access scaffold and minor snagging.
