滨海软土微观孔隙测定方法

Microcosmic Determination Method of Coastal Soft Soil

土体孔隙结构是其重要物理力学指标,对研究土体变形、破坏有重要意义。通过室内试验(SEM、CT技术)及数值模拟(Arc GIS)对滨海软土的孔隙结构、孔径大小及分布进行研究,就土体在分级荷载下的二、三维孔隙结构进行探讨。将基于CT试验的Arc GIS三维孔隙率、PCAS统计的SEM二维孔隙率、利用SEM二维图像计算的三维孔隙率、压汞试验实测孔隙率进行对比,分析不同方法测定孔隙率的精确度。同时对SEM图像进行测量和分析,统计不同孔径的孔隙数量随荷载的变化规律,从而分析软土的固结机理和微宏观力学性质。研究表明:随竖向荷载增大,土体大孔隙逐渐被压缩,孔隙平均直径逐渐减小,总孔隙体积减小,结构单元之间变得紧密,表观孔隙率减小。土体的轴向、径向和体积的收缩变形是由于孔隙的压缩以及颗粒的变形引起的,同时孔隙的分形维数受孔隙的压缩和颗粒的影响较大,周长-面积法求取孔隙的分形维数受阈值选取影响,但体积-面积法不受阈值选取的影响。

The pore structure of soil is an important physical and mechanical index,which is of great significance for studying the deformation and destruction of soil. The pore structure,pore size and distribution of coastal soft soil were studied by laboratory test( SEM,CT technique) and numerical simulation( ArcGIS). The two-dimensional and three-dimensional pore structure of soil under hierarchical load were discussed. The three-dimensional porosity of ArcGIS based on CT test,the SEM two-dimensional porosity of PCAS statistics,3 D porosity calculated using SEM two-dimensional image,and the measured porosity of mercury intrusion test were compared to analyze the accuracy of different methods for determining porosity. At the same time,the SEM image was measured and analyzed,and the variation of the number of pores with different pore sizes with the load was statistically analyzed to analyze the consolidation mechanism and micro-macro-mechanical properties of the soft soil. The research shows that with the increase of vertical load,the large pores of the soil are gradually compressed,the average diameter of the pores is gradually reduced,the total pore volume is reduced,the structural units become tight,and the apparent porosity decreases. The axial,radial and volumetric shrinkage of the soil is caused by the compression of the pores and the deformation of the particles. At the same time,the fractal dimension of the pores is greatly affected by the compression of the pores and the particles,and the pores are determined by the perimeter-area method. The fractal dimension is affected by the threshold selection,but the volume-area method is not affected by the threshold selection.