寒区隧道合理保温型式及保温效果试验
Rationality of heat preservation mode in cold region tunnels and model test verification

寒区隧道常常受到冻融循环破坏,合理的保温型式能有效减小隧道冻害发生。在实测温度场基础上根据冻土学原理,运用Stephen公式推导围岩最大冻结深度,并结合传热学中等效厚度换算法推导内置式和外置式保温层厚度计算公式,进行对比分析,结合工程实例计算得到围岩冻深为2.62 m,内置式和外置式保温层厚度分别为3.54 cm和4.61 cm,内置式保温型式更经济。运用自主研发的室内试验模型开展了环境温度-12.5 ℃无保温层、-12.5 ℃内置3.5 cm聚氨酯保温层、-20 ℃内置3.5 cm聚氨酯保温层3组工况试验。结果表明:环境温度-12.5 ℃未设保温层时围岩将会逐渐冻结,内置式3.5 cm聚氨酯保温层保温效果良好;环境温度-20 ℃内置式3.5 cm聚氨酯保温层保温效果变差但仍能满足短期围岩不发生冻结。研究结果可为寒区隧道保温设计提供依据。
Cold region tunnels are often destroyed by freeze-thaw cycles, setting appropriate thermal insulation layer can effectively reduce the occurrency of tunnel freezing injury. According to the principle of frozen soil, and the stephen formula, the maximum freezing depth of surrounding rock was calculated. Combining with the equivalent thickness conversion method, the calculation formula of the thickness of insulation layer was deduced. Based on the engineering example, calculated thickness of built-in thermal insulation layer is 3.23cm. Using the independent Indoor model testing 3 groups working condition of experiment, the environment temperature is -12.5 ℃ no thermal insulation layer, -12.5 ℃ built-in 3.5 cm polyurethane thermal insulation layer, and 20 ℃ built-in 3.5cm polyurethane thermal insulation layer, verifying the theoretical calculation value. The results show that the environment temperature is -12.5 ℃ surrounding rock frozen without thermal insulation layer, built-in 3.5 cm polyurethane insulation heat preservation effect is good; When the environment temperature -20 ℃ built-in 3.5 cm polyurethane insulation heat preservation effect variation but can still meet the short-term surrounding rock not freeze. The results can provide evidence for design of cold region tunnels