Study On Mechanism Of Effect Of Sand Modification On Salt Leaching Of Coastal Clay Saline Soil

This study takes the coastal clay soil in the Yellow River Delta as the research object.In order to solve the problem of poor structural structure,poor physical properties,low soil saturated hydraulic conductivity,unfavorable soil salt leaching,and A large number of engineering sediments that are common in the Yellow River Irrigation District of the Yellow River Delta are difficult to treat and difficult to handle.We conducted experiments and theoretical studies on the improvement of coastal clay soil by using sediment from sedimentation.The study uses a combination of indoor simulation experiments,theoretical analysis and field experiments.We designed a soil column salt leaching test,a soil saturated hydraulic conductivity test and a soil moisture characteristic curve test under different sand distribution conditions.It is used to clarify the effects of different particle composition changes on desalination efficiency,saturated hydraulic conductivity and soil macroporosity of coastal clay soil.In order to explore the mechanism and measures for the improvement of coastal clay soil by sand matching improvement,the main results of this research include the following aspects:(1)The particle composition of the coastal clay soil is quite different from that of the yellow sediment.When the clay soil is modified with sand,the content of each grain in the soil sample changes significantly.The content of three fine fractions of fine sand,coarse powder and fine clay in soil samples is the most significant,the content of very fine sand of 0.1-0.05 mm is obviously improved,the coarse powder of 0.05-0.01 mm and the fine of <0.002 mm.The clay content is significantly reduced.(2)Using the gray correlation method to find the three grain sizes that have the greatest influence on soil macroporosity.Determine the order of strength of these three levels of action,The intensity of the action is from very large to small,fine sand,fine sand,coarse powder.The study found a significant linear correlation between these three particle sizes and soil macroporosity,and established a regression equation.(3)Soil saturated hydraulic conductivity increases with increasing soil macroporosity.There is a significant power function relationship between soil macroporosity and soil saturated hydraulic conductivity in coastal clay soil.In the indoor three-rinse test test,The soil desalination efficiency increases with the increase of soil saturated hydraulic conductivity,and there is a significant logarithmic function relationship.(4)The study clarified the mechanism of sand and soil improvement in clay soil.Viscous saline soil sand modification can affect soil macroporosity,soil saturated hydraulic conductivity,and ultimately affect soil desalination efficiency by changing soil particle composition.(5)In this study,the gray correlation method was used to find out the three particle sizes that have the greatest impact on soil desalination efficiency,and determined the order of the three grain strengths.The intensity of action is from coarse to small,coarse sand,medium sand,fine sand,There is a significant linear correlation between these three particle sizes and soil desalination efficiency.(6)One year after the field sand improvement,The degree of salinization of soil treated with each sand was significantly reduced.Among them,S1,S2,S3 and S4 in the field can effectively reduce the soil salinity of the soil 0-20 cm surface layer and 0-60 cm plough layer under evaporation conditions.And in the three years of field sand improvement,the winter wheat yield under the field has been significantly improved.In particular,in 2017,S3 increased production by 77.65%.