基于四参数随机生长法重构土体的渗流细观数值模拟

Reconstructed soil meso-numerical seepage simulation based on quartet structure generation set

基于四参数随机生长法(QSGS),根据土体孔隙率,重构土体微观结构.通过格子Boltzmann方法,左右采用不透水边界,上下边界采用非平衡外推格式,颗粒之间的碰撞采用标准反弹格式,建立饱和土体渗流模型,并让恒定流速的水渗入模型.结合算例,推导了宏观物理单位与格子单位之间的转换关系,编制相关Matlab程序,并且进行运算分析,探讨在计算机模拟情况下的微观土体结构中水的渗流变化规律.结果表明:根据QSGS方法所重构的土体生成过程与自然环境下多孔介质的生成过程类似,重构土体性状各异,连通性和结构与实际土体类似;在连通性良好的前提下,土体中水的渗流速度与孔隙率大小有关;同一土体中渗流通道越小的位置水的渗流速度越小,渗流通道越大的位置渗流速度越大;在相同孔隙率条件下,大颗粒土的平均渗流速度比小颗粒土的平均渗流速度大,而小颗粒土的渗流更为稳定.

Based on quartet structure generation set（QSGS）,and according to the soil porosity,soil microstructure is reconstructed.By the lattice Boltzmann method,using the impermeable boundary on the left and the right,the upper and lower boundaries adopting the non-equilibrium extrapolation format,the collisions between particles using Bounce-back scheme,the saturated soil percolation model is established,then water with a constant flow rate penetrates the model.Combined with examples,the conversion relationship between macroscopic physical units and lattice units is derived,the relevant matlab program is worked out,and the operational analysis is conducted to explore the water seepage variation of micro-soil structure in computer simulations.The results show that： The generating process according to QSGS reconstructed soil is similar to that of the porous medium in the natural environment,reconstructions of soil traits vary,connectivity and structures are similar to the actual soil.Under the premise of good connectivity,the seepage velocity is relative to the porosity.The smaller theposition of the seepage channel in the same soils,the smaller the water seepage velocity is; the larger the position of seepage channel,the larger the water seepage velocity is larger.In the same porosity condition,the average seepage velocity of large grained soil is greater than that of the small grained soil,and soil seepage of small grained soil is more stable.