固结条件下软黏土微观孔隙结构的演化及其分形描述

利用扫描电镜(SEM)研究软黏土固结前后的微观结构,采用数字图像技术研究软黏土固结过程中微孔隙的大小、数量及其分布的演化规律.基于Sierpinski地毯的分形概念,结合量测数据给出了描述孔隙结构的Sierpinski分维数并研究其差异性.图像分析表明,随着固结压力的增大,软黏土的孔隙度和孔径趋于减小,孔径范围变窄,土体固结过程对孔隙级配具有一定的调节作用.分形研究表明,分维数的数值大小反映了软黏土固结过程中的孔隙度变化,固结压力愈大,孔隙度愈小,分维数愈大.分维数与孔隙度、固结压力、压缩量之间存在较为显著的线性回归关系,并能反映软黏土的结构性特点.研究结果揭示了土体宏观变形与微孔隙结构分形特性之间存在的相关关系,分维数可为软黏土固结变形预测提供依据.

Evolution of micro pore structure of soft clay and its fractal features under consolidation

The internal structure of unconsolidated and consolidated soft clay was studied by using scanning electron microscope(SEM). A digital imaging method was applied to investigate the evolution of pore size, pore number, pore size distribution and pore number distribution of soft clay in the process of consolidation according to the SEM images. Based on the fractal concept of Sierpinski carpet the Sierpinski fractal dimension Ds, characterizing the structure of soil pore, is obtained from the measured data, and its variation following the change of pressure is investigated. The image analysis shows that the porosity and pore size decreases as the consolidation pressure increases, and the range of pore size becomes narrower. The consolidation process of soft clay has an effect of adjusting the gradation of micro pore. The study result on fractal shows that the magnitude of Ds reflects the variation of porosity of soft clay under consolidation. Large fractal corresponds to large consolidation pressure and small porosity. Obvious linear relationships between Ds and porosity, consolidation pressure and consolidation deformation respectively. So that Ds reflects the structure characteristics of soft clay. It is concluded that the magnitude of fractal can be utilized to predict the consolidation deformation of soft clay.