Experimental study on migration and deposition characteristics of fine particles in sandwich sand under seepage condition
The problem of migration-deposition of fine particles in sandy soils with interbedded layers is widespread in groundwater recharge,infiltration of piles,design of reverse filtration layer and grouting.Using an indoor one-dimensional sand column test system,three kinds of sandy soils with typical grain sizes were selected,and the migration-deposition characteristics of suspended particles in sandy soils were investigated in two kinds of interlayer locations and thicknesses.The results show that the particle size has a significant effect on the migration-deposition process of fine particles in sand columns with interlayers.When the particle size ratio is larger than 1,the peak value of the suspended particles penetration curve is higher,and the amount of fine particles deposited in the interlayer increases abruptly;the closer the interlayer position is to the water injection end,the smaller the thickness is,and the larger the peak value and the sudden increase in deposition are.When the particle size ratio is less than 1,the peak value of the suspended particles penetration curve is lower,and there is no particle enrich-ment at the interlayer;the closer the interlayer is to the water outlet end,the greater the thickness,and the higher the peak value of the penetration curve.During the test,the migration and deposition of suspended particles will cause changes in the permeability coefficient.The process of permeability coefficient change corresponds to the change of penetration curve,and the process is divided into three kinds:deposition,stripping migration and dy-namic equilibrium.Fine particles are deposited in sandy soil by adsorption and accumulate at the adsorption.
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