大断面盾构隧道混凝土构件的耐火试验研究

Research and analysis on fire resistance test of the concrete component in large section shield tunnel structure

研究了大断面盾构隧道混凝土构件在火灾条件下的温度变化规律。根据汕头市苏埃通道工程的实际结构,通过立式火灾试验炉及卧式火灾试验炉,对盾构隧道的管片接缝、衬砌牛腿及排烟道顶隔板进行了耐火试验。试验中采用RABT升温曲线,测量了盾构隧道不同混凝土构件在耐火试验中的温度-时间分布曲线。结果表明:管片接缝的温度随管片缝隙宽度减小而降低,管片缝隙宽度越小,在火灾中受到的影响越小;在衬砌牛腿耐火试验中,衬砌牛腿植筋处的温度较低,而靠近火源的混凝土表面的测点温度较高,受火面的混凝土出现了局部损伤,需对牛腿结构受火面进行防火保护;在顶隔板耐火试验中,顶隔板内部温度沿厚度方向呈非均匀分布,靠近受火面的温度高,上部区域温度与中部区域温度相差不大,受火面侧已经有部分厚度的混凝土受到局部的损伤。研究结果可为盾构隧道结构设计优化和其他类似工程提供参考。

In this paper,the temperature variation of the concrete components in the large section shield tunnel under fire conditions is studied. According to the actual structure of the Suai tunnel project in Shantou,fire resistance tests were carried out on the segment joint,the corbel,and the slab of the smoke exhaust duct through a vertical furnace and a horizontal furnace.In the fire resistance test of the segment joint,the RABT curves were adopted to measure the temperature vs time curves of the concrete components in the shield tunnel. The results show that the inner temperature of the segment joint decreases with decreasing the width of the gaps,which indicates that the lower the width of the segment joint is,the less influence it is in the fire.In the fire resistance test of the corbel,the temperature at the planting bar of the corbel is lower,while the temperature at the measuring point on the surface of the concrete near the fire source is higher,and part of the concrete on the fire surface is damaged. So it is necessary to carry out fire protection on the fire surface of the corbel. In the fire resistance test of the slab of the smoke exhaust duct,the internal temperature of the slab is nonuniformly distributed along the thickness direction. The temperature near the fire surface is higher,while the temperature of the upper area is not much different from the temperature of the middle area and the fire surface side is locally damaged. During the fire resistance test of the slab,the deflection of the slab almost shows a linear change. Since the slab is only subject to its weight,the deflection value generated is small. This paper can provide a reference for the optimization of shield tunnel structure design.