myGeobrugg
Systems
Year of installation
2022
Initial situation
Wadhurst Cutting (city end) is located along the Tonbridge to Hastings railway line in East Sussex and has provided key transport links between London and Hastings for the past 170 years. Following a number of failures of an oversteepened cutting in 2014, 2016 and 2019, both at the city end and country end of the cutting, which are separated by a short tunnel BAM was engaged to install an approved solution (designed by Byrne Looby) to remediate the cutting. The initial emergency works were undertaken on the country end of the cutting and are not detailed here.
Instability originated from over-steepening sections of the cutting, which is made up of the Wadhurst Clay Formation (clay/mudstone) and the Ashdown formation (sandstone & siltstone).
Geology
Geology on site consisted of the Wadhurst Clay Formation which is primarily a mudstone which had weathered to clay in the upper section where it had been exposed to continuous weathering. Underlying the mudstone are sandstone and siltstones of the Ashdown Formation.
Description
Due to the size and complexity of the project, with
- heights of the cutting ranged from 8 - 18 meters
- approximately 300 meters in length
- a tunnel portal at the southern extent of the site
a range of geotechnical solutions was installed. Given the proximity to the track, part of the works was completed in a seven-day blockade of the line in October 2021.
Extensive soil nailing was undertaken around the tunnel portal, where nails between 10 - 12 meters in length were installed. Prior to soil nailing, TECCO G65/3 mesh was laid as a temporary protection measure to prevent any loose material from falling onto the track during drilling; the mesh was then drilled through as nails were installed.
On both the cutting's up and down lines, approximately the upper 6 - 8 meters of the faces were remediated using an active soil nailing (28 mm diameter) and meshing (TECCO G65/3). Due to the contouring of the existing slope creating a slight overhang, below this section, down to track level was remediated with a passive drape system (TECCO G65/3) with regular nailing along the base of the slope along with some intermittent profiling nails.
The result was across the entire cutting (city end), over 16,000 square meters of TECCO G65/3 was installed, and over 14,000 meters of soil nails and rock bolts were drilled (across approximately 3000 locations). Going forward, the remediation will ensure fewer disruptions to rail users while also increasing staff and public safety on the railway for its 60-year design life.
Country/Region
United Kingdom
Customer
Engineering
Contractor
Protected object
Railway
Corrosion protection
GEOBRUGG SUPERCOATING
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