重塑非饱和黄土浸水入渗规律的模型试验研究

Model test study on infiltration law of remolded unsaturated loess

为了研究非饱和黄土的浸水入渗规律,开展了重塑黄土的浸水入渗模型试验,分析了浸水过程中不同位置的体积含水率变化及湿润锋面发展过程,研究了入渗水分在水平和径向的发展变化规律,并通过考虑空气压力的Green-Ampt模型计算得到不同时间的入渗深度,与实测值进行对比分析。研究表明:不同测点的体积含水率变化趋势基本一致,都会经历稳定-快速增长-到达峰值-快速减小-再次增长-维持稳定6个阶段;浸水入渗过程受入渗深度、渗流路径、沿程黏滞阻力和空气压力的共同影响,入渗深度越深、距离中心轴位置越远、湿润锋发展越滞后,入渗速率越小。深度从0 cm增加至100 cm时,入渗速率从14.93 cm/h减小至1.67 cm/h。对不同位置的竖向入渗速率与入渗深度的关系进行拟合发现:竖向入渗速率与入渗深度呈二次方关系,且拟合度达到0.9以上;径向水分运移是该深度水分径向扩散和上部水分竖向入渗综合作用的结果,故相比于竖向入渗较快;模型计算结果中湿润锋面发展趋势与实测竖向入渗情况一致,但入渗后期的入渗深度计算值比实测偏大。研究结果可为黄土地基浸水入渗研究提供参考。

In order to study the infiltration law of unsaturated loess,the infiltration model test of remolded loess is carried out,the change of volume moisture content at different positions and the development process of wetting front are analyzed,the development and change law of infiltration water content in horizontal and radial direction is studied,and the infiltration depth at different time is calculated by Green-Ampt model considering air pressure,which is compared with the measured value.The research shows that the change trend of volume moisture content at different measuring points is basically the same,and it would go through six stages:stability-rapid growth-reaching peak-rapid decrease-regrowth-maintaining stability;and the immersion infiltration process is affected by infiltration depth,infiltration path,viscous resistance and air pressure.The deeper the infiltration depth and the farther away from the central axis,the more delayed the development of wetting front and the smaller the infiltration rate.As the depth increases from 0 cm to 100 cm,the infiltration rate decreases from 14.93 cm/h to 1.67 cm/h.The relationship between vertical infiltration rate and infiltration depth at different positions is fitted,and it is found that the vertical infiltration rate and the infiltration depth have a quadratic relationship,and the fitting degree is above 0.9.Radial water migration is the result of the combined action of radial water diffusion and vertical water infiltration in the upper part of the depth,so it is faster than vertical water infiltration.The development trend of wetting front in the model is consistent with the measured vertical infiltration,however,the calculated value of infiltration depth is larger than the measured value at the late infiltration stage.The research results can provide reference for the study of loess foundation infiltration.