海底隧道管节结构防火试验与数值模拟

Fire-proof Test and Numerical Simulation on Tube Structure of Subsea Tunnel

以港珠澳大桥工程海底隧道为依托,采用明火试验与数值模拟方法研究了隧道管节结构在火灾下的温度分布及防火技术方案。基于被动隔热技术设计了玻镁防火板单层拼装与双层错缝拼装、保全板单层拼装、防火涂料单层喷涂等3种类型多种试验工况,测试了管节结构构件表面、钢筋保护层等关键位置的温度变化,得到了不同防火方案的隔热效果。基于有限元热传导瞬态分析方法,研究了小汽车、公交车、重型货车、RABT曲线4种典型火灾对管节结构的温度影响,得到了有、无防火板条件下管节结构体内的温度梯度、衰减规律与火灾影响深度,论证了防火隔热对管节结构火灾安全的保护效果。结果表明：防火涂料存在易掉落等现象;玻镁防火板单层拼装方案下,试验构件表面温度超过380℃,不满足耐火极限要求;玻镁防火板双层拼装与保全板单层拼装方案可以满足耐火极限要求,但需做好填缝等构造要求;无论何种隧道火灾升温曲线,管节结构内温度呈现负指数衰减形式;在双层玻镁板隔热条件下,结构受温影响深度为15~20cm,无隔热措施时,结构受温影响深度约为30cm。

Based on the Hong Kong-Zhuhai-Macao Bridge（HZMB）project,fire experiment and numerical simulation were used to analyze the temperature distribution and fire-proof technical solution for subsea tunnel tube structure.According to passive thermal insulation technique,three types of staggered assembling of single-layer or double-layer magnesium board,single-layer assembling of preservation board and single-layer ejected fire-proof coating were designed under different conditions.Temperature changes of structure surface and reinforcement protective cover were measured for researching the thermal insulation effects under different fireproofing solutions.Based on finite element transient analysis method of heat transfer,four different fire disasters known as car,public bus,heavy truck and RABT temperature curves were used to analyze the effect of high temperature on tube structure.The temperature gradient,attenuation rule and influenced depth of internal structure with or without fireproofing board were obtained,and the protective effect of fireproofing board on structural fire safe was proved.The resultsshow that the ejected coating is likely to fall by high temperature.Under the test of single-layer magnesium board,tube structure surface temperature has exceeded 380 ℃ which doesn＇t satisfy the fire endurance need.In the contrast,the test results of double-layer magnesium board and single-layer preservation board can well meet the requirement of fireproofing limit,but some construction requirements like gap filling between fireproofing boards should be firstly considered in the design scheme.Whatever temperature curve it is,the temperature distribution inside tube structure manifests a negative exponential delay.Under the condition of double-layer magnesium boards,the temperature influencing depth is 15 to 20cm thickness.Under the condition of no fireproofing boards,the temperature influencing depth is 30 cm thickness.