Network Rail Case Study
Geotechnical Appraisals following Storm Events
PROJECT NAME: Walkover Surveys
NETWORK RAIL ROUTE(S): LNW
SERVICES: Geotechnical Appraisal and risk evaluation walkovers following storm events
CLIENT: Network Rail
During CP5 our company supplied one of our Senior Engineers to the Network Rail LNW RAM team (Geotech, Drainage & off-track, Structures) to provide a support role to their in-house Asset Managers. Our Senior Engineer, as well as others within the company, are certified Earthwork (EWE3) and Structure (STE4) Examiners.
During the time following Storm Desmond, we conducted a walkover survey of the CBC1 line between St Bee’s and Sellafield to assess the damage caused to Earthworks, Structures and Coastal Defences. The CBC1 at this location is a twin track line with a line speed of 40mph which follows the coast. Particular attention was given to the overtopping and erosion around hard coastal defences, as well as defects to the sea walls. Many areas of earthwork failure were encountered, with damage to rock armour, rock blankets, sea walls and culverts paramount.
At Braystones there was a small settlement of beach houses that formed an informal sea defence to the railway. Many of the houses were destroyed in the storm with subsequent damage to the earthworks supporting the railway behind. Many areas of the rock armour along this section of coastline placed to protect the railway line was washed away in the storm.
Our Engineer was on site for approximately 3 weeks supervising the installation of replacement rock armour by Murphy’s, one of Network Rail LNW routes minor works contractors.
Also encountered as part of the inspection were numerous culverts and outfalls that were completely blocked with beach debris from the storm.
These were subsequently cleared and returned to full operational condition in the weeks that followed by the minor works contractor.
Many areas of the natural slopes and earthworks suffered from loss of material from the toe, with some resulting in shallow translational failures. Sections of concrete retaining wall were undermined with erosion of material from behind them reducing the support of the track structure above.
A large masonry retaining wall near St Bees suffered from the washout of mortar joints with evidence of minor hollows opening up behind.
A programme of emergency remedial works was devised, and the retaining wall fully repaired without any loss of service.
Following the site inspections our Engineer was involved as part of a team of Network Rail Route Asset Managers in undertaking a review of the coastal defences along the entirety of the Cumbrian coastline and contributed to a programme of improvement works to many areas along the coast which have now been implemented.