Abstract
Hanshin Expressway Public Corporation is constructing a highway in Kyoto. This highway passes through a heavily populated residential area including two railways and a river. Therefore, this part is planned by TBM shield tunnel. This Fushimi Tunnel is 855 m long and the inner diameter is 10.1 m. The lining of Fushimi Tunnel is originally designed by RC segment and secondary concrete in place. However, the design is altered from the RC segment to thinner steel-concrete composite segment and the secondary concrete lining is omitted. The excavation volume of the tunnel can be reduced nearly 20% by this change, but fire protection measure for the tunnel becomes necessary. The tentative fire requirement for Fushimi Tunnel is that temperature of the lining must be lower than 350 degrees C in concrete and 300 degrees C in steel. This paper reports the results of a fire test done for the composite segment with various fire protection measures. Each test specimen consists of two segments jointed together in the circumferential direction and they are prestressed in compression corresponding to the design load. These segments are identical to the segment to be used for the Fushimi Tunnel. Each segment is 2.5 m long, 1.5 m wide and 0.25 m thick. The fire protection measure applied is board type, silica fiber blanket type and spray mortar type. These specimens are tested under RABT fire curve in which the maximum temperature is kept to be 1200 degrees C for 1 h. This given energy corresponds to about 100 MW. Specimen without fire protection is also tested for comparison. Temperature of the specimen during the test is recorded and the phenomenon of spalling is also recorded by video camera. After testing, the inner face of each specimen is observed. The concrete strength and carbonation depth are measured by cores taken from each tested specimen. Through the fire test, the following information is obtained on the steel-concrete composite shield segment. Spalling of concrete occurs and it reaches up to 60 mm if there is no fire protection on the surface. Compressive strength of the concrete drops to one half of the unheated value and Young's modulus to one quarter by the heating. Carbonation of concrete occurs by portlandite resolution at the place where the temperature becomes over 500 degrees C. The temperature of the steel girder and the joint metal well exceeds the limit of the fire requirement if no fire protection is installed. The sealing material for water tightness is destroyed by fire if no fire protection is installed. All the selected fire protections of the board type, silica fiber blanket type and spray mortar type keep the temperature of the segment less than 260 degrees C. The temperature of the joint metal is kept lower than 100 degrees C and the sealing for water tightness is protected unharmed. It is important to install fire protection on the surface of composite segment such as tested in this study even if fireproof concrete is used for the segment. All the fire protection measures adopted in this fire test satisfy the tentative fire requirement of Fushimi tunnel. (A). Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.
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