软土孔隙微观结构的分形研究

Fractal Approach on Soft Soil Porosity Microstructure

根据分形模型的构造方法,提出了孔隙度分维、孔隙分布分维及孔隙边缘形状分维,用以描述软土微结构SEM图像中孔隙的变化情况.利用数字图像处理与分析的方法研究了软土加固前后3种分形维数的变化趋势,发现软土加固后3种分形维数随深度增加有减小趋势,说明软土加固后孔隙的分布面积减少,结构单元体之间排列紧密,孔隙尺寸分布趋于均匀,孔隙边缘趋于光滑.结果表明:软土中孔隙分布及其形状具有分形特征,不同的分形维数可以从不同角度反映土体的加固效果及力学特性变化,为由微观结构反映土体的宏观力学性能提供了桥梁.

Based on the creation of fractal model, three kinds of fractal dimensions, i.e. , porosity density dimension, porosity distribution dimension and porosity edge shape dimension, were proposed to describe the variations of porosity in a soft soil microstructure SEM （spherical environment mapping） image. With the image processing and analysis methods, these fractal dimensions of un-reinforced and reinforced soft soils were investigated. The investigation shows that the fractal dimensions of reinforced soft soil diminish in different degrees. This indicates that the distribution area of porosity decreases, the structure units of soft soil array more tightly, the size distribution of porosity becomes uniform and the edge of porosity turns smooth. The research results show that the distribution and the shape of porosity in soft soil hold a fractal feature. Different fractal dimensions indicate the reinforced effectiveness and the mechanical performance variation of soil mass from different views so as to build a connection between the microstructure of soil and the macro mechanics performance of soil mass.