基于AHFO技术的毛细水运移模型验证试验研究

为了验证常用的描述毛细水运移模型的准确性,设计了室内模型试验,采用主动加热光纤法(简称AHFO)对砂土模型中的毛细水运移进行了测试。根据测试结果,分析了毛细水入渗模型Green-Ampt模型、Terzaghi毛细水上升模型和毛细水最大上升高度预测模型Lane模型、Peck模型的特点和预测精度。试验分析结果表明:对于砂性土,毛细水上升过程可以分为两个阶段,第一阶段(约前50 h),Green-Ampt模型和Terzaghi毛细水上升模型预测的毛细水上升高度值均低于实测值,Terzaghi模型拟合精度高于Green-Ampt模型;第二阶段(约50h后),Green-Ampt模型和Terzaghi模型预测值均高于实测值,且Green-Ampt模型拟合精度高于Terzaghi模型。这两个模型预测精度随时间的变化现象是与其所用的假设条件和土体物理性质变化有关。Peck模型的误差低于Lane模型,为2.60 cm,而Lane模型由于只考虑了有效粒径D10,误差高达8.58 cm。利用Green-Ampt模型可反演土的饱和渗透系数与湿润锋处基质吸力。研究成果为常用毛细水运移模型选择和误差分析提供了实测依据。

Experimental study on capillary water transport model based on AHFO technology

In order to verify the accuracy of commonly used capillary water transport models, several laboratory model tests are carried out based on the active heated fiber optic method (AHFO). During these tests, the soil moisture profiles determined by capillary force are measured using AHFO. Based on the experimental results, the characteristics and prediction accuracy of Green-Ampt and Terzaghi models are analyzed, so as to describe the moving rate of capillary water. In addition, the Lane and Peck models that predict the maximum capillary heights are evaluated as well. The results indicate that for sand, the capillary water rise process can be divided into two stages. During the first stage (first elapsed 50 hours), the predicted capillary water heights by the Green-Ampt and Terzaghi models are lower than the measured values collected by AHFO, and the accuracy of Terzaghi model is higher than that of the Green-Ampt model. During the second stage (after 50 hours), the predicted values are higher than the actual measured ones, and the Green-Ampt model has a higher accuracy. This accuracy change with time depends on model assumptions and physical properties of soils. The results also suggest that the error of the Peck model (2.60 cm) is lower than that of the Lane model (8.58 cm). The saturated hydrologic conductivity of the soils and the matric suction at the wetting front can be calculated by the Green-Ampt model. These discoveries provide basic data for selecting effective and high-precision models to reflect capillary rise in soils.