植被发育斜坡土体大孔隙三维重构模型渗流场的LBM数值模拟

以云南昭通头寨植被发育斜坡土体为研究对象，结合CT扫描试验与数字图像处理技术实现了其三维大孔隙空间结构模型的重构。然后基于格子Boltzmann方法（LBM）的D3Q19模型，将固体土骨架视为渗流场边界，并设置反弹格式的边界条件模拟土骨架与水分间的相互作用，从细观角度研究了水在植被发育斜坡土体大孔隙中的渗流特性。研究结果表明：土体渗流过程中，在大孔隙纵向连通的通道内形成了优先流，且通道中的流速远超其他部位；而在封闭或者连通性差的大孔隙中导水率极小，流速几乎为0。土体中大孔隙通道内的流速由孔壁至通道中心逐渐增大，且流速与至通道中心的距离近似呈二次抛物线的分布特征。沿深度方向土体切片大孔隙率大的截面平均渗流流速Uz也较大，从整体变化趋势来看，截面大孔隙率与平均渗流流速有相似的变化规律，这充分说明植被发育斜坡土体内的大孔隙分布对土壤沿深度方向的渗流特性有重要影响。

Numerical simulation of macropores seepage field in the 3D reconstruction model of well vegetated slope soil based on LBM

Taking the well vegetated slope soil in the Touzhai of Yunnan province as case study, a 3D macropores structure model is reconstructed based on the CT scanning and digital image processing technology. Then the soil skeleton is taken as the boundary of seepage field, and the bounce-back scheme is set to simulate the interaction between soil skeleton and water. The lattice Boltzmann method is applied to study the seepage behavior in the macropores of well vegetated slope soil. The results show that the preferential flow is formed in the channel with good longitudinal connectivity, and the flow velocity in the channel is larger than that of other regions. In the closed macropores or these with poor connectivity, the water conductivity is small and the flow velocity almost equals to zero. The flow velocity in the channel increases gradually from the wall of macropores to the center of the channel, and the relationship between flow velocity and distance to the center of channel is approximately quadratic parabola. Along the depth direction, the section with larger macropores porosity has the faster average seepage velocity of Uz. Overall, there is the similar trend for the section macropores porosity and the average seepage velocity, which indicates that the distribution of macropores in the well vegetated slope soil influences significantly on the seepage characteristics along the depth direction.