AH-FBG法用于毛细水运移规律的温度效应研究

Effect of Temperature on Capillary Water Migration Using the Actively Heated Fiber Bragg Grating Method

摘要

毛细水运移作为非饱和土体水分运移的重要形式，其动态特征直接影响土体的力学性质，并与多种地质灾害、环境岩土问题密切相关．地下水位以上的土体温度分布往往存在差异，进而对毛细水运移速率产生影响．为了探究毛细水运移规律的温度效应，本研究利用主动加热光纤布拉格光栅(AH-FBG)法开展室内模型试验，在定水头条件下，通过控制加热桶与常温桶的温度变量监测土体中毛细水运移过程，并对不同温度条件下土体的体积含水率分布变化进行对比，分析温度效应对毛细水运移的影响．研究结果表明：在一定时间内，毛细水上升高度随时间增加而升高，湿润峰出现的位置标志着该时刻水分运移的最远位置；土体温度升高对毛细水运移具有促进影响，土体温度越高，毛细水上升同一高度所需的时间越短，毛细水上升速率越高；湿润锋界面作为状态界面，在运移过程中具有动态变化特性，温度升高会显著促进湿润峰界面的运移速率；毛细水湿润锋界面变化及其温度效应与外界环境条件紧密相关，是工程建设中不可忽视的运动与状态界面．

Abstract

Capillary water migration is one of the key mechanisms of moisture migration in unsaturated soils. Its dynamic characteristics directly influence the mechanical properties of soils and are closely linked to various geological hazards and environmental geotechnical issues. The temperature distribution in soils above the groundwater table is often heterogeneous, which influences the rate of capillary water migration. To investigate the effect of temperature on capillary water migration, indoor model experiments were conducted under constant head conditions using the actively heated fiber Bragg grating(AH-FBG)method. By controlling the temperature difference between a heated water reservoir and a reservoir maintained at an ambient temperature, the capillary water migration process in the soil was studied. The volumetric water content distributions of soil at different temperatures were compared to analyze the influence of temperature on capillary water migration. Results showed that over a given period, the rise height of capillary water gradually increased with time and the location where the wetting front appeared marked the furthest extent of water migration at that moment. High soil temperatures promoted capillary water transport. In particular, high temperatures led to less time being required for capillary water to reach the same height, resulting in a high rate of ascent. Moreover, the wetting front was a state interface that changed continuously with water migration over time. An increase in the temperature notably increased the migration rate of the wetting front. The wetting front interface, along with its temperature effect, was highly influenced by external environmental conditions and played a critical role in engineering construction as both a motion and state interface that could not be ignored.

关键词

毛细水运移 / 主动加热光纤布拉格光栅法 / 体积含水率 / 湿润锋 / 温度效应 / 状态界面

Key words

capillary water migration / actively heated fiber Bragg grating(AH-FBG) method / volumetric water content / wetting front / temperature effect / state interface

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基金资助

国家自然科学基金青年科学基金资助项目(42307189)

中国博士后科学基金资助项目(2024T170215)

中国博士后科学基金资助项目(2023M740974)

江苏省地质工程环境智能监控工程研究中心开放基金资助项目(2023-ZNJKJJ-11)