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基于格子Boltzmann方法,采用D2Q9基本模型,上、下边界采用非平衡外推格式,左、右不透水边界及土颗粒采用反弹格式设置边界条件,对土体细观渗流场进行数值模拟。首先将试验测得物理单位的数据转化为格子单位,然后用Matlab编制程序,对CT扫描切片进行处理,生成土体细观的数据结构,最后把格子单位表示的结果再转为物理单位,分析了渗流流速的变化规律,得到了整体和局部渗流场的分布情况。分析结果表明:(1)孔道处的流速U随着入渗时间的延长而逐渐达到一个相对稳定值,进而得到流体从开始入渗至稳定状态经历的准确时间T;(2)平均渗流速度由入口处沿y轴负方向逐渐递减,且小于入口处的平均渗流流速;(3)渗流量主要受控于通道的连通性、孔隙大小,最大渗流速度集中在通道的窄孔道处,封闭的孔道和孔隙渗流速度为0。格子Boltzmann方法能有效地对CT扫描得到的2D切片进行数值模拟,可以定量、准确地研究真实土体渗流场的变化机制。
Based on the lattice Boltzmann method, the basic model of D2Q9 is adopted. The upper and lower boundaries adopt the non-equilibrium extrapolation format, the left and right impervious boundaries and the soil particles set the boundary conditions by the rebound format. Firstly, the data of the physical units measured in the experiment were transformed into lattice units, and then the program was compiled by Matlab to process the CT scan slices to generate the mesoscopic data structure of the soil. Finally, the results expressed by the lattice units were converted into physical units and analyzed The variation law of seepage flow rate, the distribution of global and local seepage fields are obtained. The results show that: (1) the flow velocity U at the tunnel gradually reaches a relative steady value as the infiltration time prolongs, and then the accurate time T from the initial infiltration to steady state can be obtained; (2) The inlet decreases gradually along the negative direction of the y-axis and is less than the average seepage velocity at the entrance; (3) the seepage volume is mainly controlled by the connectivity of the channel, the pore size and the maximum seepage velocity are concentrated at the narrow channel of the channel, And pore seepage velocity is zero. The lattice Boltzmann method can effectively simulate the 2D slices obtained by CT scanning, and can quantitatively and accurately study the variation mechanism of the seepage field of real soil.