The chalk cliffs at Dover form a vital element of the Kent Downs Area of outstanding natural beauty, a nationally important and protected landscape. Samphire Hoe is a new piece of land created by Eurotunnel during the construction of the Channel Tunnel.
Samphire Hoe cutting has a history of rockfall, with previous failures landing on the track.
The design remit was to extend the life of the earthwork such that there is a reduced likelihood of speed restrictions or line closure due to rockfall.
Tactile inspection by Fairhurst revealed the main mechanisms of slope instability to comprise ravelling across the slope face, caused by surface weathering and preferential erosion of weaker chalk horizons, together with more localised toppling, wedge sliding and planar sliding failures of individual blocks.
Working alongside Fairhurst - Consulting Structural and Civil Engineers of Glasgow CAN Geotechnical Ltd. undertook the installation of 13 individual Geobrugg rockfall barriers. The GBE range of barriers were chosen for their ease of installation. Their low anchor forces meant shorter anchors with the resultant decrease in drilling time, allowing for a far shorter program. The strict vertical drop testing and certifications that come with these fences meant that the only choice of supplier was the world leading technology innovator Geobrugg.
Rockfall analysis was undertaken by Fairhurst and the system energy and height were specified from this point forward. In total 785 metres of GBE-500A and 446 metres of GBE-1000A have been installed between Abbotscliffe and Shakespeare Tunnels. The barriers were used in combination with localised areas of Geobrugg high tensile TECCO® SYSTEM³ flexible facing in total 3150 square metres of TECCO® G65/3 and 350 pieces of P33 system spike plates were installed.