土中水平渗流AHFO方法监测试验研究

土中的水平渗流影响着土体的结构强度,受测试技术的限制,目前还缺少有效的手段对其水平运移规律精确测定。采用基于分布式测温技术(DTS)的主动加热光纤法(AHFO),设计室内模型试验,测试土中一维水平渗流过程中含水率的变化,拟合了渗流时间与湿润锋运移距离、累积入渗量以及入渗率之间的关系,并对测试结果进行了评价。结果表明:利用AHFO可对任一时刻的湿润锋位置进行准确定位,湿润锋水平向运移距离与时间的关系满足Green-Ampt模型;利用AHFO法所测水平向含水率分布积分所得的累积渗入量与量筒所测实际加水量之间具有很好的一致性,累积渗入量与时间对数呈线性关系;入渗速率随着时间增长逐渐减小,与入渗时间平方根间可用一反比例函数描述。

Experiment study on horizontal seepage monitoring in soil using AHFO method

Horizontal seepage in soil affects the structural strength of soil. With limitations of measuring technology, there is still lack of effective means to accurately measure water infiltration in soil. In this paper, the actively heated fiber optic (AHFO) method based on the distributed temperature sensing (DTS) technology was adopted. A laboratory model test was carried out to monitor the change of soil moisture content during a one-dimensional horizontal infiltration process. The relationship between the elapsed time and (i) advanced distance of wetting front, (ii) cumulative infiltration volume and (ii) infiltration rate was investigated. The horizontal soil moisture profiles measured by the AHFO method were evaluated based on the classic Green-Ampt model. The results indicate that AHFO can be used to accurately locate the wetting front, and the relationship between the horizontal advanced distance of wetting front and elapsed time can be described by the Green-Ampt model. There is a good consistency between the cumulative infiltration amount obtained from horizontal integration of soil moisture content measured by the AHFO method and the actual charging amount gauged by a measuring cylinder. The cumulative infiltration amount and elapsed logarithmic time are linearly dependent. The infiltration rate decreases with elapsed time, which can be described by an inverse proportional function. The AHFO method used in this paper has the potential to monitor infiltration in embankments and slopes, and to evaluate their stability which are primarily determined by water infiltration.