Resarch On Fractal Model Of Soil Structure Based On Particle Size Distribution And Pore Parameters

China’s power system,with a complex distribution structure,has a wide range of radiation.Ground fault often occur and results in different degrees of economic and casualties.As the important factor to determine the grounding performance,soil impedance is influenced by many factors.So it is difficult to get the experimental results of soil impedance changing with a single factor through macro experiment.As the basis of simulation analysis of soil physical properties,soil microstructure model has been widely used in soil transport,seepage and other aspects.The establishment of soil model suitable for the study of soil electrical conductivity has an important guiding role in the design of lightning and grounding protection.And a little literature involves in this area.Therefore,this paper establishes an improved fractal model based on some soil structure parameters,which lays a foundation for the study of grounding protection,ion transport and porous dielectric electrical materials.The paper focuses on the following aspects:Based on Fractal Theory,classcial soil fractal model is introduced and have such problems as accurate self-similarity or uncontrollable porosity distribution.Theχ²-test is used to verify that the porosity of the Random Sierpinski Carpet Model has non-normal distribution.In addition,the influence of the disordered iterative pattern on the overall porosity in the first fractal is too heavy,which leads to model porosity with a large discrete.As the main parameters affecting soil conductivity.Different samples from a certain area or a certain type of soil in nature will have different porosity,but the statistical value of the overall sampling results will be normal distribution.For solveing above problem in the classical model,Lower-Weighted Non-uniform Iterative Fractal（LNIF）Model is proposed,which effectively reduce the randomness of model porosity and guarantee the normal distribution.From the perspective of probability theory and mathematical statistics,the influence of the input parameters on the distribution characteristics of LNIF Model porosity is analyzed.The relations between the input parameters and the average and variance of porosity distribution are obtained.The method to control the model input parameters is obtained.A water adsorption program is proposed.The influence of adsorption probability on the uniformity of water distribution is analyzed.Combined water adsorption program and input parameter control method,a Controllable Fractal Modeling（CFM）Method based on actual soil structure parameters is proposed.The maximum difference of particle size,porosity and water content of LNIF Model is successfully controlled by adopting CFM Method.The influence of particle adsorption on the range of solid particles is studied.The range of solid particles is larger thand^k-1,which meets the control conditions of the range.In the model,there is a phenomenon of grading distribution of solid particles,the grading standard of solid particle area is determined,the size and content of solid particle area in different particle size range are calculated,and the characteristics of particle content distribution are analyzed.