Study On Microscopic Pore Structure Of Red Clay In Southern Guizhou Based On SEM

Red clay is the most widely distributed soil type in karst area of guizhou,and its pore structure determines the hydraulic parameters of soil,such as water conductivity,water characteristic curve and hydrodynamic dispersion coefficient.In recent years,the rapid development of SEM detection and image information technology has become a powerful tool for the study of soil microstructure,but the quantitative characterization of guizhou red clay microstructure based on SEM is still in the exploratory stage.Therefore,guizhou red clay microstructure SEM detection and fractal analysis,to explore the microscopic pore structure of red clay and the relationship between the macroscopic physical properties,not only to provide certain theoretical depth cognition of red clay in guizhou microstructure application according to the methods and techniques,and key zone in guizhou karst soil erosion and desertification control,ecological environment protection and groundwater pollution prevention and control technology has important reference value on the solution of the problem.In this paper,red clay in the south of guizhou province was taken as the example research object.Six representative red clay samples were collected in the field.Firstly,particle analysis test,mercury injection test and scanning electron microscope test were used to analyze the distribution rules of soil particle size and pore microstructure.Secondly,IPP(image-pro Plus)Image technology was used for information processing,classification,calculation and analysis of SEM microstructure images to obtain 3d structural parameters of red clay.Finally,the quantitative characterization of the micro-pore structure of red clay was studied by means of mathematical statistics and fractal theory.The main research results of this paper are as follows:1.The particle analysis test results of six groups of red clay soil samples showed that the minimum particle size of soil particles was 0.049 microns,and the maximum particle size was 69.61 microns.Among them,the particle size distribution of 0.119 microns ～ 0.933 microns was the most concentrated,accounting for 67.6% ～ 72.9%.Soil samples can not simultaneously satisfy the uneven gradation of soil(Cu≥5),and the gradation curve is continuous(Cc=1 ～ 3),which belongs to the poor gradation soil,and determines the nature of poor soil permeability.2.According to the analysis of mercury injection test data,for red clay samples with different dry densities,the cumulative mercury volume is inversely proportional to their dry densities,and the aperture analysis range is 0.005 bedroom meters 340 bedroom meters.Red clay can be divided into four categories,respectively,micro pore(< 0.01 microns),small pore(0.01 microns ～ 3 microns),medium pore(3 microns ～ 60 microns)and large pores(> 60 microns),the small pore development,red clay proportion is as high as 62%,small pore and outer load under the condition of deformation is not big,confirm the high porosity of the red clay is flooded,the macro physical and mechanical properties of low compression.3.IPP image processing technology was applied to extract the characterization parameters of micro-pore structure of red clay above 0.1 microns through SEM scanning electron microscope image information processing and classification,and the micro-structure of red clay was divided into four spatial structure types: flocculent structure,lamellar structure,skeletonlike structure and coagulite structure.4.pore abundance mainly distributed in more than 0.4 ～ 0.6(39.0% ～ 41.9%),greater than 0.6 ～ 0.8(23.8% ～ 29.1%)of these two interval,show that red clay of microscopic pore structure in the majority with oval shape,elongated and the porosity of the shaft type less,the pore is randomly distributed in the red clay,it reflects a structural unit in a ball of irregular arrangement form.The measurement results of the directional frequency of the samples showed that the distribution of the pore directional frequency at different sample points was different in each interval,but the directional Angle of the pores was distributed in each interval without significant difference.5.Based on the fractal dimension theory,the relationship model between the microporosity of red clay and the fractal dimension was established.The calculation results showed that the Sierpinski fractal dimension of red clay was between 1.84 and 1.90,and the fractal dimension decreased with the increase of the porosity.The fractal dimension of Korcak ranged from 0.60 to 0.76,and the fractal dimension increased with the increase of the number of micropores.The Menger fractal dimension of red clay is between 2.935 and 2.967,and the fractal dimension decreases with the increase of porosity.