CONSTRUCTION of the Channel Tunnel Rail Link (CTRL) through Kent requires excavation of several deep cuttings.
Working with the CTRL Contract 330 main contractors Alfred McAlpine/Amec jv, geotechnical product supplier Maccaferri provided the Armater cellular containment system to support soil and vegetation on the sides of soil nailed cuttings.
The section shown is the Temple Wood cutting near the River Medway. Located in poor ground, it has an upper slope gradient of 1:2. 5 through the superficial deposits with a 1:1 gradient over an 8m high lower slope. The lower slope in chalk contains clay infilled solution features. Soil nails ensure overall stability of the clay materials, while Armater secured to the surface helps vegetation establish quickly on the steep slopes.
Lightweight, flexible and easy to install, Armater forms cells into which topsoil is placed. These cells reduce erosion caused by surface run-off and prevent formation of gullies. The porous material enables water to flow slowly through the hexagonal cells, avoiding ponding at the base of the cell.
The Armater was laid after soil nailing and secured to the slope surface using 0. 5m long, 10mm diameter steel pins and buckles at 1m centres. An hydraulic excavator placed topsoil in the cells and the project was finished offby hydroseeding.