A Study On Characteristics Of Unsaturated Sandy Soils Based On The CT Scanning Method

In the hydrologic cycle,sandy soil is an important junction of surface water and groundwater,especially in arid areas which is lack of water.Therefore,it is meaningful to study the soil water in the unsaturated zone for water soil conservation and ecological environment protection.At present,in the field of soil physics,CT scan is used to study the soil hydraulic properties that is in a blank state.Applying industrial CT high-resolution instruments to do a quantitative research about the microstructure of porous media and fluid motion law has become a new research direction in the field of materials science.Basing on the latest industrial CT scan instrument called XTH225 ST,this study scans the five samples of sand(quartz sand,coarse sand)to focus on the soil microstructure.This test uses the VG-Studio and Image J software to handle the image data.The software can identify the solid particles,water and air,and analyze particle size distribution and moisture content of cross sections.Contrasting four quartz sand sections,it can be concluded that the optimal particle size is 1 to 2 mm under CT scan.According to the quantitative analysis of the porosity,with the decreasing particle size,the same soil's total porosity also will increase.Using the artificial recognition and VG-Studio software's transferring phenomenon module handle the CT scan image,and we can get the diameter of the equivalent capillary and the equivalent of capillary water.We can have a conclusion that for the same sand column and the same material,the average level of capillary water equivalent diameter is smaller than the capillary equivalent diameter with other things being equal.For the different particle size of sand column,the size of the average pore diameter also increases with the increase of particle size in the same other conditions.The research select 1-2 mm CUGB coarse sand to do the moisture absorption and emancipation experiment.When it reached the stability,we can get the unsaturated characteristic curve of soil moisture by CT scanning analysis.Because of the existence of the lag phenomenon,the characteristic curve of soil moisture will be a "circle".And it can also provide some parameter values for the Van Genuchten formula.3D distribution of capillary water in the sand column is complex,and its winding path likes many "worms" creeping in the soil.The method of CT scan can skip over the traditional experiment,and directly find out the relationship between moisture content and matrix suction called characteristic curve of soil moisture.Furthermore,it can improve the efficiency.And it provides a new way of getting the water distribution characteristics of unsaturated soil.