Experiment And Numerical Simulation Of Soil Water And Salt Transport Under Different Groundwater Levels In YinBei Area

The soil salinization in our country is becoming more and more serious,its main distribution is in north of China,northwest of China and coastal areas,and the most prominent is ni ningxia region.Based on the example of the town named swallows in ningxia,which is used to analyze the dynamic variations of water salt migration before and after the evaporation of the area,the mathematical model of soil water salt removal in the area is established with a numerical simulation of the soil water salt migration in the area already completed to figure out the changes in soil salinization in the area.(1)In the process of establishing the mathematical model of soil water salt migration,a lot of soil hydrodynamic parameters need to be used.These parameters are determined by experiments.The water characteristic curves were fitted with VG and GM.Comparing the two fitting models,it is concluded that the fitting of the soil water curve in this region is more suitable than the VG model.At the same time,the water diffusivity and hydrodynamic dispersion coefficient parameters were obtained by using horizontal soil column suction method.To measure the moisture content of soil and the measured values of diffusivity for fitting,it is concluded that the fitting curve of the correlation coefficient is 0.9367,and the exponential function is more suitable to express,making fitting precision more higher.(2)When doing soil column vertical infiltration test in the laboratory,according the basic data of hydrogeology and groundwater mineralization degree,a suitable model test scheme combined with the corresponding mathematical model was accomplished to determine the suitable soil hydraulic characteristic parameters for the model in the study area,analysising the process of water and salt dynamic change law in the study area The numerical model was constructed by using a finite volume method,and it's applied to a specific example in the case of the different discrete format,and the total implicit format is more suitable for the discrete processing of the model.In solving the problem of water movement in unsaturated soil,finite volume method is more advantageous in solving the problem.(3)The dynamic changes of soil water and salt migration influenced by many factors.First of all,the analysis of characteristics of soil water and salt migration in the monitoring area under different soil depth before evaporation and after the evaporation was done.Then on the basis of the indoor model experiment,a two-dimensional numerical model for soil moisture migration equation was constructed by using the discrete finite volume method,choosing the selection of appropriate discrete format,using high precision algorithm to discrete equations.The data of the field experiment from July to December were compared with the simulated values to verify the reliability of the model.The dynamic quantitative analysis of groundwater and soil water and salt variation law in saline-alkali land was finished through numerical simulation,thus more scientific advice of resoring the saline-alkali land in northern Yinchuan is given in this research.