土壤水分特征曲线模型对数值模拟非饱和渗流的影响

土壤水分特征曲线直接影响非饱和渗流场压力水头和含水率的预测结果。Brooks-Corey模型和van Genuchten模型是目前运用最广泛的土壤水分特征曲线模型。本文给定三种不同质地土壤(粘土、砂土和砾石)的BC模型参数,根据Morel提出的BC模型与VG模型等价的参数关系计算出VG模型参数。采用上述两模型分别对这三种土壤进行了均质土柱的入渗过程模拟。两种模型的计算结果有一定差别。三种土壤土柱的VG模型湿润锋推进速度都比BC模型大。由于粘土的初始含水率接近饱和,BC模型和VG模型的渗流场差距最大。粘土土柱上表面压力水头的变化幅度BC模型小于VG模型,而含水率的变化幅度BC模型大于VG模型。砂土和砾石土柱上表面压力水头和含水率的变化幅度都为BC模型大于VG模型。砂土土柱BC模型和VG模型的渗流场差距随入渗时间的持续而加剧。

Effect of soil water characteristic models on numerical modeling of unsaturated flow

When numerical models are used to simulate unsaturated groundwater flows, distributions of pressure head and water contents are greatly dependent on the soil water characteristic curve (model). Brooks-Corey model and van Genuchten model are the most widely used soil water characteristic (curve) models. For three different kinds of soils (clay, sand and gravel), the parameters in van Genuchten model were computed from the known parameters in Brooks-Corey model according to the parameter equivalence given by Morel. Applying these two models, a case study of numerical modeling of infiltration into a homogeneous soil column was carried out. There were some differences in seepage field between the two models. The movement of wetting front of VG model was greater than BC model for three kinds of soils. The differences between the two models were maximum in clay column, because the initial water content was very near saturation. For clay column, the variation range of pressure head of BC model was less than VG model, while the variation range of water content of BC model was greater than VG model. The variation range of pressure head and water content of BC model were both greater than VG model in sand column and gavel column. The differences in sand column became larger as infiltration time went on.