HS2 C1 - North and South Porous Portal

The current package of work involves the construction of the 4nr Chiltern Tunnels' porous portals. One porous portal is made up of 2nr 500m stamped concrete wall from 4.5 to 7.4m high and 1nr 500mm thick curved concrete roof (inner diameter of 4.55m). There is one 240m and one 160m long portal at each end of tunnel (16km apart). Specific formworks have to be designed and supplied, allowing portals realisation while TBMs are boring and supplied. The package includes also the North Portal base slab (thickness 2m x 57...