Secondary stainless steel framework, Clyde Tunnel
Stainless reinforcement bar used in Cradlewell Underpass
Tunnels need to function relatively maintenance-free for many decades. Stainless steel requires no added protection for corrosion resistance and its high strength and fire resistance provide a long and durable service life. Stainless steel is used in both visible applications, such as fire doors and barriers, and invisible applications such as reinforcing.
Glasgow's Clyde Tunnel provides a major transport link, used by more than 65,000 vehicles each day. During a refurbishment that was completed in 2010, a secondary framework was created from grade 316 (1.4401) stainless steel. The framework supports a stainless tunnel lining which, in the event of a fire, is designed to keep the temperature within the tunnel below 300°C.
Located near the coast, the underpass at Cradlewell, Newcastle is another UK example where over 250 tonnes of grade 316 stainless steel was used in the tunnel deck and upstands for its ability to resist corrosion.