基于土体细观结构重构技术的渗流场数值模拟

真实土体的细观结构由许多个大小不一的土颗粒团组成，传统四参数随机生长法（QSGS）构建的土体结构土颗粒团比较均匀，与实际情况存在较大的差异。为弥补这一缺陷，考虑土体孔隙率及自相关函数的影响，对传统的四参数随机生长法进行改进，实现了更接近于真实土体的细观结构重构。在此基础上基于格子Boltzmann方法，采用D2Q9模型，通过设置模型入口、出口边界为非平衡态外推格式，左右边界及土颗粒边界为标准反弹格式的边界条件，建立了模拟重构土体细观渗流场的二维模型。同时，针对一算例编制了相应的计算程序，研究了恒定流速入渗情况下重构土体的细观渗流场。研究表明：土体的渗流方向优先选择连通性较好孔隙所形成的通道，流速受控于通道整体连通性的优劣。整体贯通型的通道流动速度较快，部分连通的孔隙中其流动速度相对较慢。即使局部孔隙空间较大，其渗流速度仍取决于是否位于贯通型通道上。

Numerical simulation for seepage field of soil based on mesoscopic structure reconfiguration technology

The mesoscopic structure of real soil consists of numerous particles with different sizes, and yet the traditional reconstruction method of quartet structure generation set (QSGS) produces relatively uniform soil particles，which has significant discrepancy with the actual mesoscopic structure of soil. In order to remedy this deficiency, the QSGS is improved by considering the influences of porosity and autocorrelative function of soil, so that the mesoscopic structure reconfiguration closer to real soil is obtained. Based on the reconfiguration model combined with Lattice Boltzmann method , the D2Q9 model is applied to construct a two dimensional model for simulating mesoscopic seepage field of reconfiguration soil by setting the non-equilibrium extrapolation scheme at the inlet and outlet boundaries, and the bounce-back scheme at the soil particles’ boundary as well as the left and right boundaries. Meanwhile, according to a case study, a corresponding program is developed to simulate mesoscopic seepage field of reconstructed soil with constant inlet seepage velocity. The results show that the pore fluid preferentially flows through the channel with good connectivity. Meanwhile, the flow velocity is controlled by the whole connectivity of the channel. The velocity is much faster in whole-through-channel than that in partial-through-channel. Even if there exists a large pore space, the velocity still depends on whether or not it is on the channel with integral connectivity.