HC Deb 06 January 2004 vol 416 c219W
Jonathan Shaw

To ask the Secretary of State for Transport what the thickness was of the invert of the North Downs Tunnel approved by the Channel Tunnel Rail Link Act 1996; and what change there has been in the specification.[145977]

Mr. McNulty

The Channel Tunnel Rail Link Act 1996 contains no specifications of the tunnel lining thickness. The specifications relating to such details in the North Downs Tunnel were first drawn up later. The tunnel has a concrete lining with a relatively flat invert and reinforced concrete base slab, which supports the ballasted track. The concrete is about 1 metre thick in the invert and the average ballast thickness is 600 mm.