摘要
草炭土是在地表积水环境下植物残体经氧化和部分分解作用而堆积形成的一种特殊的腐殖质土。含大量植物纤维的草炭土具有高渗透性、高孔隙比、高含水率等不良工程地质特性。为了探究草炭土的孔隙特征与其孔隙内部的渗流规律,本文以吉林省敦化地区草炭土为研究对象,通过CT扫描技术获取草炭土样的CT序列图像。采用试凑法,通过Mimics的mask体积计算功能并结合土体的真实孔隙率确定了图像二值化的最优阈值,并得到了更接近土体的细观结构的三维重构模型。同时基于Lattice Boltzmann Method原理,在PALABOS代码库的基础上改编程序进行草炭土样的单相渗流模拟,研究了恒定压差下的土体的模拟渗透率值与渗流场的性质,并结合Paraview可视化软件分析了流线与流速在孔隙内的分布情况。研究结果表明:草炭土内部孔隙孔径大小不一,大孔径孔隙与小孔径孔隙形态各异,而植物纤维的架空状分布以及根状孔隙是土体内部形成大孔径孔隙通道的主要原因;流体在其内部流动时,优先以大孔径通道渗流,流线也集中于大孔径渗流通道,流体在大孔径通道内部的流速也高于散布的细小孔径,草炭土的渗透率主要取决于其内部大孔径的数量,因此草炭土的渗透率受到土中植物纤维的含量以及分解度的影响,植物纤维的含量越多,分解度越低,草炭土的渗透率越高,反之则越低。
Turfy soil is a special kind of humus soil formed by oxidation and partial decomposition of plant residues in the environment of waterlogging.Turfy soil contains a lot of plant fibers,and is with adverse engineering geological characteristics such as high permeability,high pore ratio and high-water content.In order to investigate the pore characteristics of the turfy soil and the percolation law,CT sequence images of turfy soil in Dunhua,Jilin Province are obtained.The optimal threshold of image binarization is determined using the mask volume calculation of Mimics and porosity of turfy soil.The 3 D reconstruction model is constructed.Meanwhile,based on the Lattice Boltzmann Method principle,the PALABOS code is adopted to conduct the single-phase seepage simulation of the turfy soil.In addition,the differences of simulated permeability values and the seepage field of the soil under constant pressure are studied.The distribution of flow lines and flow velocity within the pore space are analyzed.The results show that internal pores in turfy soil vary in size.The large pore size and small pore size exhibit different patterns.The distribution of plant fibers and root-like pores are the main reason for the formation of large pore size channels in turfy soil.Therefore,the permeability of turfy soils is mainly affected by the content of plant fibers in the soil and the degree of decomposition.The more content of plant fiber,the lower the decomposition degree is and the higher the permeability of turfy soil is,and vice versa.
作者
杨圣涛
吕岩
贺元源
刘婷婷
马晓祯
YANG Shengtao;LüYan;HE Yuanyuan;LIU Tingting;MA Xiaozhen(College of Construction Engineering,Jilin University,Changchun 130026,China)
出处
《工程地质学报》
CSCD
北大核心
2021年第5期1354-1365,共12页
Journal of Engineering Geology
基金
国家自然科学基金(资助号:41502272)。
关键词
草炭土
CT扫描
三维重构
植物纤维
LBM
渗流模拟
Turfy soil
CT scanning
3D reconstruction
Plant fibers
Lattice Boltzmann Method
Seepage simulation
