冻融条件下路基温度场和湿度场分布式感知试验

Laboratory Study on Temperature Field and Moisture Field Distributed Sensing of Subgrade in Freezing and Thawing

摘要:

搭建土体冻融多物理场感知室内试验装置，布设传统点式传感器和分布式光纤，对土体冻融过程中路基温度场、湿度场和变形情况开展试验监测，探究单端冻结、双端融化条件下土体温度场和湿度场的分布式感知特征，验证主动加热分布式光纤技术的监测效果。试验结果表明，-15 ℃单端冻结条件下，土体冻结过程按降温速率分为快速冷却、逐步降温、稳定平衡三阶段，冻结锋面逐渐下移，最大冻深约占土柱高度的35%。孔隙水受冻胀迁移力影响向冻结锋面移动，引起冻融前后土体湿度场重分布，并导致土体冻胀变形，变形量为土体最大冻深的7.8%~10.9%。分布式光纤可准确得到冻融过程中土体温度场、湿度场变化特征，识别土体内冻结区域范围，温度、湿度监测拟合优度R²分别达0.98和0.94。

Abstract:

In this paper， a laboratory test device for multi-physical field sensing during soil freezing and thawing was established. Traditional point sensors and distributed optical fibers were used in the test to monitor the temperature field， moisture field， and deformation of the subgrade during freezing and thawing process. Distributed sensing characteristics of the temperature and moisture fields of the soil under single-ended freezing and double-ended thawing condition were investigated， and the monitoring performance of the active heating distributed optical fiber technology was verified. The results show that， under the condition of -15 ℃ single-ended freezing， the soil freezing process is divided into three stages according to the cooling rate， i.e.， the rapid cooling stage， the gradual cooling stage， and the stable equilibrium stage. The freezing front gradually moves down during freezing， and the maximum freezing depth is about 35% of the height of soil column. The pore water is affected by the frost heave migration force to the freezing front and causes the redistribution of soil moisture field before and after freezing and thawing， thus causes frost heave deformation of the soil， which accounts for 7.8 % to 10.9 % of the maximum freezing depth of soil column. The distributed optical fiber can accurately obtain the characteristics of the soil temperature and moisture fields during the freezing and thawing process， and identify the range of the freezing area in the soil. The goodness of fit R² of temperature and moisture monitoring reaches 0.98 and 0.94， respectively.