【作者】 陈伟；

【导师】 姚仰平；

【作者基本信息】 北京航空航天大学 ， 建筑与土木工程， 2020， 硕士

【摘要】 在冬季寒冷季节,地表温度低于土体内部温度,土中水汽在温度梯度作用下向上迁移,当地表有机场跑道,公路,建筑物基础等的覆盖层时,迁移的水汽无法到达地面,在覆盖层下聚集,形成锅盖效应。对沈阳桃仙国际机场跑道进行工程勘探时发现道面下碎石层中水分大量聚集,引发了道面冻胀开裂,不均匀沉降的危害。基于该工程案例,进行了室内试验研究,根据室内试验需要对北航自行研制的冻融循环锅盖效应仪进行了改进,采用改进后的仪器展开了细砾中的锅盖效应试验研究,发现覆盖层下细砾中有大量水分聚集,结合沈阳桃仙国际机场的工程案例,推测该机场道基碎石中聚集的水分是锅盖效应导致的,并进行了室内试验模拟该机场跑道的锅盖效应致灾过程,分析了致灾机理。本文主要结论有:(1)对马氏瓶的回流原理展开了分析,推理出引起马氏瓶回流所添加水量的计算式,并结合试验对计算式进行了验证,揭示了马氏瓶回流过程的规律。(2)通过进行细砾中的锅盖效应试验,发现在低温期水汽迁移至覆盖层下冷凝凝华的速度较稳定;细砾中的持水量与温度场有关,土样顶部温度越高,持水量越少。(3)模拟沈阳机场跑道道基结构铺设试验土样,采用冻融循环的温控模式模拟沈阳机场的季节冻融循环。试验结果表明:在低温冻结期顶部控制温度越低,冻结锋面越深,水汽迁移速度越快,覆盖层下生成的凝华冰和冷凝水越多。试验中马氏瓶补充的水量可认为等于锅盖效应生成的水量。更多还原

【Abstract】 In the cold winter season,the surface temperature of the soil is lower than that of the internal temperature,and the vapor in the soil migrates upward due to the temperature gradient.the vapor cannot migrates to the ground and accumulates beneath a pavement where the local surface is covered by an airport runway,highway,building foundation,Which forms pot-cover effect.During the engineering exploration of the Shenyang Taoxian International Airport runway,it was found that a large amount of moisture was accumulated in the gravel layer below the road surface,which caused the danger of frost heave cracking and uneven settlement of the road surface.laboratory tests based on this project case were carried out.The pot-cover effect apparatus with freezing-thawing cycles developed by Beihang was improved according to the needs of the tests.Experimental study on pot-cover effect in the gravel were carried out with the improved instrument,and a large amount of moisture was gathered in the gravel under the cover.Combined with the engineering case of Shenyang Taoxian International Airport,it is speculated that the moisture accumulated in the gravel of road foundation at the airport was caused by the pot-cover effect,and an laboratory test was performed to simulate the disaster process of the pot-cover effect at the airport runway,and the mechanism of the disaster was analyzed.The main conclusions of this article are:1.Analysis of back-flow principle of Mariotte bottle was carried out,the amount of water reflow to Mariotte bottle calculation equation is obtained.And the equation has been verified by experiments.The study reveals the mechanism of water reflow process in Mariotte bottle.2.The conclusions were revealed by experimental study on pot-cover effect in the gravel.the rate is relatively stable of moisture accumulation beneath a pavement of condensation or desublimation.The amount of absorbed water in the gravel is related to the temperature distribution in the soil.The higher of temperature of the soil at the top,the less amount of water was absorbed.3.The laying structure of experimental soil is similar with the structure of foundation of Shenyang Taoxian International Airport runway,and the mode of the temperature control of the freeze-thaw cycle is used to immitted to the seasonal cycle of the Airport.The test results show that the lower the controlled temperature at the top of soil,the deeper of the freezing front,and the more condensation ice and condensate generated under the cover.The amount of water supplemented by the Mariotte bottle can be considered to be equal to the amount of water generated by pot-cover effect.更多还原