Quantitative Analysis Of Evolutionary Mechanism Of Micro-pore Structure Of Soft Clay Under The Isotropic Consolidation

The micro-structure of soil is an important factor to determine their mechanical properties, therefore, the study of the micro-structure has greatly theoretical and applied significance in the soil engineering evaluation system. However, the micro-structure of soil is a very complex porous structure, existing research tools are difficult to describe and simulate them accurately. In view of this, with the help of the special research foundation of doctorial subjects in university of China (No.20070497107), based on the isotropic consolidation and permeability test, by using scanning electron microscopy (SEM) and IPP image processing technology, the qualitative and quantitative research for evolution mechanism of micro-pore structure in the consolidation process of soft clay were conducted. In this paper, the research methods and main results are as follows:(1) The development history, current situation and research trends of the micro-structure and the fractal theory of soil were summarized in this paper, and the background and significance of the topic were briefly introduced.(2) Throught the isotropic consolidation tests of the original state of soft clay under different consolidation pressures, the relevant mechanical parameters were received, and the disturbance samples of before and after the consolidation test samples were produced to conduct the permeability test, the results showed that:the permeability coefficient had exponential relationship with consolidation pressure, the higher the pressure of consolidation, the smaller permeability coefficient of the disturbance sample; the temperature and diversity of soil had a greater influence on the permeability coefficient, the preliminary view showed that:if the water temperature were below 10 temperature, the higher the temperature, the greater the permeability coefficient.(3) The qualitative research about morphology of micro-structure of each samples before and after consolidation test were researched by using SEM, based on the study of SEM, the quantitative research was made to analyze the indicators of pore and regularities of distribution by the use of IPP image technology, which were size, number, area, porosity, surface fractal dimension, roundness, and so on. The results showed that:under the isotropic consolidation, the flocculation structure of the micro-structure of soft clay changed into the tight structure, and with the increase of the consolidation pressure, the porosity, pore size, distribution of pore size and total volume of pore progressively got smaller, which promoted the mutual adjustment of pore size distribution. In addition, the surface fractal dimension showed normal distribution, and its curve to had the trend of the left shift, at the same time, the roundness showed the trend of exponentially decreasing.(4) Based on experimental research, the fractal study of soft clay was made by using the model of Sierpinski carpet, the relationship between the fractal dimension and the parameters of micro-pore, the indicators of mechanical properties and permeability were investigated. The results showed that:soft clay had the obvious fractal characteristics, with the increase of consolidation pressure, the porosity reducted, Sierpinski fractal dimension increaseed. Fractal dimension and the consolidation pressure, porosity, the volume of pore and the deformation of consolidation had a more visible linear relationship, the fractal dimension and permeability coefficients showed a more pronounced exponential growth relationship. This showed that the fractal dimension could be used as a new parameters to reveal variation of parameters of mechanical properties and micro-structure evolution mechanism in the process of consolidation.