基于分形理论的非饱和土多相流相对渗透系数模型

相对渗透系数是描述非饱和土水力特性的重要参数之一,然而在传统非饱和土相对渗透系数研究中着重研究了湿润相的渗流特性,而非湿润相的渗流特性研究较少。为研究非饱和土壤多相流运移特征,将土壤孔隙简化为一簇服从分形定律的迂曲毛细管,通过建立液相与气相在多孔介质中的输运特征模型,结合Young-Laplace方程与Buckingham-Darcy定律得到了非饱和土的液相与气相的相对渗透系数模型。该模型仅包含2个参数,其物理意义明确且均可通过试验测得。最后通过8组试验数据对提出的模型进行验证,结果表明提出的模型可较好地描述非饱和土多相渗流特征,验证了其合理性与适用性。

Relative Permeability Coefficient Model of Unsaturated Soil with Multiphase Flow Based on Fractal Theory

Relative permeability coefficient is a crucial parameter describing the hydraulic characteristics of unsaturated soil. In researches of traditional relative permeability model for unsaturated soil, the seepage characteristic model of wet phase rather than non-wet phase received much focus. To study the multiphase flow transport model of unsaturated soil, we at first simplified the soil pores into a group of tortuous capillaries obeying the fractal law; by establishing the transport characteristic model of liquid and gas phase in porous media, we obtained the model of relative permeability coefficient of both liquid and gas phase of unsaturated soil in association with the Young-Laplace equation and the Buckingham-Darcy’s law. The model only contains two parameters, with clear physical meanings and can be measured by experiments. Eight groups of test data validated the rationality and applicability of the present model. We hence conclude that the model better describes the multiphase seepage characteristics of unsaturated soil.