Supporting AMCO Giffen over 8 weeks in Bristol
CAN delivered emergency rockfall protection works above a freight railway, safely removing unstable sandstone blocks before installing a permanent solution to protect the line from future rockfall.
A routine inspection of a sandstone rock face above the freight line from Bristol to Avonmouth Docks identified substantial loose blocks at imminent risk of falling onto the railway line below, which would cause serious damage.
Due to the very large block size and their precarious position the blocks needed to be removed in a controlled manner, with protection in place to the rail infrastructure below. CAN was contracted by AMCO to provide the specialist work at height and geotechnical engineering skills to implement the designed solution.
Enabling works were undertaken to clear vegetation and large trees from above and around the cliff, to remove unstable trees and reduce the risk of future root jacking causing further instability to the rock face. A temporary rock bolt, netting and cable system was sequentially installed over the worst areas of the face to help hold it together as removal work progressed.
During full closure of the railway, a protective temporary concrete block wall was constructed beneath the rock face to help contain removed material, and an additional polystyrene block and timber mat energy absorbing crash deck was installed over the line. This allowed removal of the multiple-ton blocks by jacking and levering, with the temporary works protection below ensuring no damage was caused, with material then removed from site by RRV.
On completion of the block removal, a Geobrugg RXE500 rock catch fence was installed to guard against future rock fall from the face. CAN installed the fence using lightweight drilling plant to drill the anchors for the fence posts, and implemented a complex concrete pumping system to transfer ready mixed concrete from the nearest access point to the site location to form the cast in situ concrete post bases. All works were completed without incident, on time and on budget.
