| With the rise of urban rail transit and urban underground road construction in large and medium sized cities, the tunnel construction of shield tunneling method has become more and more widely used in China. Segment joint as the weak point of this structure system, in the high temperature of fire performance degradation, which may lead to joint excessive deformation, affect the structural safety of tunnel, even lead to serious tunnel disaster.In this paper, using the prototype of large diameter shield tunnel segments, in different fire scenario such as fire size and duration, segment joint experimental study and numerical simulation are done under high temperature of fire. From three aspects i.e. segment joint concrete, joint bolt and joint rubber strips, the joint performance are studied under high temperature of fire. The achievements are as follows:(1) From apparent phenomena of segment concrete such as burst, crack, seepage, characteristics of segment injury under high temperature are analysised。The critical bursting temperature is 520～540 centigrade, concentrated burst duration time is 25-35min, maximum burst depth of different working conditions, segment crack development and segment seepage change under the time of fire, which are obtained。(2) The temperature field of segment and the segment joint are described under fire。Segment concrete temperature heating is mainly concentrated in the distance which is within 20cm to the fire surface. Along the thickness direction of the segment, the highest temperature of segment concrete distribution formula is proposed; bolt heating up slowly, which the highest temperature is about 100 centigrade. Temperature of the inner rubber strip final is up to 250 centigrade, while the outer rubber strip is less than 50 centigrade.(3) The segment joint deformation and the joint stiffness change with the time of fire. The higher temperature and the longer time of fire, the greater joint opening and the joint stiffness decreased more quickly. When the fire time is 120min, the segment joint stiffness can be regarded as 0.(4) Analysis on coupled thermal-mechanical simulation of concrete segment joint by established finite element model. Under different working conditions, numerical simulation is done for the segment joint. By comparing the numerical results with the experimental results, it is verified that the numerical simulation is in general agreement with the experimental results.(5) The criterion of segment joint damage assessment after fire is put forward, which provides reference for the establishment of tunnel fire protection code in our country. The evaluation criterion is divided into four grades:Ⅱa-minor damage, II b-mild damage, III-moderate damage and Ⅳ-destruction.(6) The relationship between water pressure, temperature and the opening amount of rubber strip is obtained. Waterproof evaluation of segment joints under fire is proposed. Compared with the designed waterproof pressure, the waterproof failure time can be calculated. When the rubber strip is opened to 8mm or the rubber temperature is up to 200 centigrade, the waterproof pressure value of the rubber strip can be considered as 0.(7) Secondary lining are put forward as the effective protection measures of shield tunnel fire. Through the joint test and high temperature rubber waterproof analysis, it is concluded that the secondary lining can effectively ensure the segment lining joint security. |
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