Basic study on the seepage control work of the waste landfill site by sheet piles for prevention of water pollution

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In this study we have carried out a series of centrifuge model tests to investigate the influence of the penetration depth of a steel sheet pile and the difference of water level between inside and outside the sheet pile on the performance in diffusion control of contaminant when a sheet pile wall penetrated into the low permeability soil layer on the high permeability soil layer. We also carried out convective hydraulic dispersion analysis based on GMS under the same condition with centrifuge model tests to compare the results of experiments and calculations. The conclusions derived from this study are below.1)The increment of time for reaching the concentration ratio of contaminant C/CO at the clay layer surface outside the sheet pile to the specified value to the increment of penetration depth of a sheet pile depends on the conditions of the soil layers. Design by existing simplified method gives both conservative and unsafe evaluations on the time for reaching varying with the specified C/CO value.2)The more penetration depth of a sheet pile, the higher performance in diffusion control of the contaminant we get. However, the performance in diffusion control of the contaminant becomes low when the sheet piles were penetrated to the depth near a high permeability soil layer which exists under a low permeability soil layer.