基于PCAS对砂土孔隙特征的识别与应用

Study on Pore Characteristics of Sandy Soil Based on PCAS

为探究砂土粒径、颗粒级配与孔隙特征的关系,采用60目、80目、100目3种规格石英砂人工配置5种类型砂土,利用激光粒度仪和电镜扫描得到5种砂土的粒径累积百分数和135张砂土断面SEM(Scanning Electron Microscope)图像,使用PCAS软件和体积分形数学公式,分别对SEM图像和5种砂土的颗粒粒径累积百分数进行分析。分析显示,砂土颗粒在0. 8~1 000、50~500、0. 8~50μm粒级的体积分形维数数值范围分别为2. 093 77~2. 294 96、1. 298 7~2. 194 25、2. 014 9~2. 280 15;砂土孔隙分形维数数值和孔隙度分别为1. 117 9~1. 133 9、0. 519 4~0. 597 2。体积分形维数数值越大,砂土的颗粒级配越优;除砂土的粒径粗细程度影响孔隙分形维数外,颗粒级配也影响砂土的孔隙分形维数,颗粒级配越优,孔隙分形维数越大;相较于砂土的颗粒粒径大小,颗粒级配是影响砂土孔隙度的主要因素,颗粒级配越劣,砂土孔隙度越大。

This paper applied 60 mesh,80 mesh,100 mesh quartz sands to make five kinds of sandy soil,utilized laser particle size meter and scanning electron microscope to obtain cumulative percentage of particle size and 135 SEM(scanning electron microscope)images of soil section,used volume fractal formula and PCAS to analyze particle size and SEM images,respectively.Results show that ranges of values about volume fractal dimension of sandy soil are2.093 77~2.294 96,1.298 7~2.194 25,2.014 9~2.280 15μm,respectively,at 0.8 to 1 000 micron,50 to 500 micron,0.8 to 50 micron.The pore fractal dimension and porosity of sand are 1.117 9~1.133 9 and 0.519 4~0.597 2,respectively.The larger the volume fractal dimension is,the better the particle gradation is.Apart from that particle size is the affected factor towards pore fractal dimension,particle size distribution also impacts pore fractal dimension of sandy soil,and the better the particle gradation is,the larger the fractal dimension of pore is.Compared with the particle size of sandy soil,particle gradation is the main factor affecting the porosity of sandy soil.The worse the particle gradation is,the greater the porosity of sandy soil is.