Three-dimensional Reconstruction And Feature Representation Of Soil Pore

The structure of soil pore affects the transmission route and mode of water and solute directly, it also decides the important factors which affect the process of soil erosion, such as water retention, permeability, water transmissibility and so on. To research the properties of pore structure in soil has great practical significance in preventing and curing soil erosion, environment protection, reducing pollution of ground water and so on. The pore-network model is one of the most important methods for modeling porous media pore space. Taking the typical red soil as an example, this paper researches the structure of soil pores larger than 50μm by analyzing soil sample which uses the digital images of the soil slice during rainfall. We analyze and identify the original images by applying the technologies of serial slices, digital image processing especially technology of 3S to pick-up the images of soil. This paper also researches how to quantitatively describe the characteristics of the pore space and a viable pore-network model is built at the platform of Visual Basic 6.0. To study the relationship between pore structure changes and soil erosion process, this paper analyzes the spatial and temporal change rule of top soil pore characteristics. The main results are as follows:(1) Our research established data structure of network model to describe soil pore space topological characteristics, regulated design restrict by detailed system analysis and design, built pore network model based on the theory of morphologic network model and pore topological characteristics. In the modeling course, we researched the key arithmetic of heightening the vertical resolve, and the judging problem of level and vertical connection, after completed the steps above, base on the theory of space topology to structure the pore network. The result of testing model indicates that, the model can truly describe space distribution and gain topological characteristics of pore in soil.(2) Based on the research of topological relationship of pore space structure, this paper analysed pore size and connectivity from the aspect of pore affect water and solute to confirm quantitative parameters which can evaluate pore structure characteristics: Equivalent Diameter, Numbers, Porosity, Length, Angel from vertical, Tortuous Complexity, Connectivity and Hydraulic radius, moreover, it realized those arithmetic compute.(3) By using the pore network model, this paper again the parameters value of pore structure which bigger than 50μm with rainfall by numerical method, and the change rules of parameters.Pore diameter: majority pore is small, pores belong to 200-400μm have the biggest area. During the process of rainfall, the number of small pores increases, bigger pore decreases and the porosity decreases continually. With the increase in soil depth, the average diameter increases gradually. Pores in soil micro-layer L1, L2 are affected greatly in rainfall.Statistic the indicators of pores longer than 2.5 mm which play the most important role in affecting water and solute transportation, and the result are: there are regular rules of those parameters. Because the soil is disturb, there are many macropore, porosity is mainly about 4-7%. The pore structure is complex, tortuous Complexityτis mainly 1-2 mm/mm; the connectivity of soil is high, the average of Eluer is about 0.2-0.8, most pores' Hydraulic radius is about 0.05-0.1 mm. Most pore network's Angels from vertical 8 are smaller than 45 degree shows that pore has a good stretch in soil. There are some longer pores' parameters are larger than the others, pores with length is 30-40 mm haveτ6.5 mm/mm, R 0.18 mm. Although these pores with larger parameters are minority, they take more important part in transporting and seeping water and solute than samller pores in soil. The 3-D parameters have rules with rainfall, Porosity, Hydraulic radius decrease, and Angel from vertical, Tortuous Complexity and Euler number increase, indicates the pore connectivity and transmission ability decreases with the increase of rainfall time. In the later of rainfall, the surface layer of soil is compacted and pore structure has no change any more, tending to steady. As a whole, the transmission ability of pore is decreasing with the rainfall.In summary, based on the analysis of data structure of soil pore structure, this paper confirmed parameters of pore fit to pore topological structure, modeled pore network model. By using the model, we gained the change rules of red soil pore structure during rainfall. This research helps to enrich the research theory of pore topological characteristics, extend the research extension of soil erosion, open out the dynamic happen and development course of soil erosion.