A Fractal Study On Soil Structure And Soil Water Movement Model

The relationship of Soil particle-size distributions and soil water retention characteristics, saturated and unsaturated hydraulic conductivity were studied in the lab. The effect of soil texture and soil structure on water retention and hydraulic conductivity has been analyzed and discussed with fractal theory. The results as follow:1. Fractal scaling of Soil cumulative mass particle-size distribution is more easy to be use to get particle-size distributions fractal dimension (Dp), This model give the dimension a strictly range :0<3.It response to filled- ability of soil particles. The texture is heavier, the Dp is too high.2. Soil particle-size distributions fractal dimension is correlative with other texture parameters. The dimension is clear line-relative with clay content and geometric mean diameter, but the line-relationship between the dimension and index of uniformity is low. The Dp is sensitive to the variety of soil texture. It can be use as a parameter to describe the variety of soil texture.3. On the basis of the A&P model, soil particle-size distributions and soil bulk density data is translated to Soil water retention characteristics. In low matric potential state, the A&P model can be use to predict water retention characteristics, but in high matric potential state, it cannot get good result. In addition of soil pore connectivity, to correct the A&P model, it can get good result in whole water content range.4.The soil structure fractal dimension (Ds) is defined to describe to soil pore connectivity. When the Ds is smaller than the Dp, soil pore connectivity is change better, when the A is bigger than the Dp, soil pore connectivity is change worse. The DS and difference between the DS and the Dp is sensitive to the variety of soil structure, they can be use to describe the variety of soil structure.5.To describe soil water movement with fractal model. The effect of Soil pore radius and pore connectivity on soil water movement was studied. In addition of pore connectivity, the prediction of unsaturated hydraulic conductivity is more improved in low water content. The change of big pore section shape has more influence on soil water movement, but in small pore channels, the influence is small, In addition of pore section shape, it can get better prediction of unsaturated hydraulic conductivity.