Some 675 m of the central section of Bjorvika tunnel includes six immersed tube elements containing three traffic lanes in each direction. Each element is 112.5 m-long, 28-43 m-wide and 10 m-high. They were built in pairs in dry dock, towed to their sea positions and finally sunk into the prepared seabed.
Each element is connected to the other, forming a continuous structure.The roof lies 8-11 m below MSL. It is the first time Norway uses this technique for a passenger traffic tunnel.
The fire protection system that Thermal Ceramics will install, creates a permanent passive protection against: physical breakdown of the structure, damages to waterproofing, and spalling of concrete.
This protection system can withstand a sudden temperature change, (caused by a water or other agents fire extinguishing), in a way that constitutes no hazard for fire and rescue crews; in case of extreme fire accident, it will also prevent catastrophic collapse of the pre-stressed concrete structures.
The fire load is dimensioned for a 300MW fire for a minimum of two hours, as per R.W.S. fire curve.
The surfaces that will be protected in the Bjorvika tunnel cover a 39,400 sq m roof, 10,850 sq m walls, and 4,950 sq m joint seals. In order to prove the performances of the passive fire protection, the FIREBARRIER 135 system passed trough one year of intensive tests.
Several tests for Fire resistance, Physical characterization and longevity ,were carried out by S.P. Swedish National Testing and Research Institute in Borås, Sweden with the supervision of the Firemaster staff of Thermal Ceramics Italiana.
To satisfy the rigorous requirements of this project, less than 40 mm thickness of Firemaster Firebarrier 135 will be needed.
This material is cement based, made with refractory materials, and it is installed by gunning; the single components are ready to be mixed with water, they are not toxic or irritant.
Incombustible, the Firebarrier 135 is alkali and sulphur resistant, and it can not be damaged by carbon dioxide, road salts or normal washing up to 150 bar water pressure.
The joints between the concrete modules are protected, from fire risks, by Thermal Ceramic’s Felt, which are high temperature resistant modules.
The life expectancy of the fire protection and mechanical anchoring is 100 years, the same as the structure of the tunnel, and its design takes into account the effects of 100,000 vehicles/day.
The official European Thermal Ceramics distributor, I.F.S., will carry out also the installation of the Firemaster lining at Bjorvika starting from February - March, 2009. Visit www. thermalceramics.com
