不同质地斥水土壤的入渗模型

为了对斥水土壤的入渗特性及形成机理作进一步研究,分别对4种不同质地的斥水土壤进行了一维土柱垂直积水入渗试验.作图分析了斥水土壤入渗过程中累积入渗量、入渗率、湿润锋的变化情况及入渗结束后剖面含水率的分布,并采用4种入渗模型对入渗率随时间变化情况作了对比;对累积入渗量与湿润深度之间的关系采用线性关系进行了描述.结果表明:与亲水土壤相比,4种斥水土壤在入渗过程中自某一时刻会出现入渗特性的改变:I-t,zf-t及z_f-I曲线均会自某点起发生转折,以此转折点可以将整个入渗过程分为转折前和转折后进行分析.Kostiakov公式可以较好地描述亲水土壤在整个入渗过程中及斥水土壤入渗转折前的i-t关系;不同质地的斥水土壤在入渗转折后入渗率变化情况差异较大;斥水土壤湿润锋与累积入渗量之间的关系可以在转折前后采用两段线性公式进行较好地描述;发现了斥水土壤剖面较上层土壤含水率大于亲水土壤的现象.

Infiltration models for different textures of water-repellent soils

In order to study the infiltration characteristics and mechanism in water-repellent soils deeply, one-dimension vertical infiltration experiments were conducted on water repellent soils with four different textures. The accumulation infiltration, infiltration rate and wetting front length were analyzed by using diagram when the infiltration was in progress, the soil moisture profiles were examined as well. The correlation between infiltration rate and time was predicted by means of four different models and compared with the measurements. The relationship between accumulation infiltration and wetting front length was described by a linear function. The results showed that for those hydrophobic soils there is a time instance at which the infiltration characteristic is changed. Thus the infiltration process can be divided into two stages: fore-stage and post-stage. The Kostiakov equation can describe the i-t relationship of hydrophilic soils and that at the fore-stage of hydrophobic soils very well, compared with the other models. Different hydrophobic soils show relatively large difference in infiltration rate during the post-stage of infiltration. The correlation between wetting front depth and accumulation infiltration can be described by a linear model in each of the two stages for hydrophobic soils, respectively. An effect, which the soil moisture in the upper-layer of hydrophobic soil is higher than hydrophilic soil,was observed.