Calculation of the permeability coefficient of clay soil in the Langfang land subsidence area
Clay soil can be found in the weak permeable layer of underground aquifer systems,which has the function of blocking water flow and solute migration.The question of how to obtain the hydraulic parameters of weak permeable layer has gradually become a research hotspot.The permeability coefficient of clay soil is an important hydraulic parameter in the calculation of groundwater seepage and consolidation.In this work,through borehole sampling and geotechnical test,the permeability coefficient and other geotechnical test data of 52 groups of clay soil samples buried within 75 m of the Langfang settlement area are obtained.The test data show that within a 75 m burial depth,the permeability coefficient of the clay soil varies from(0.001 5～0.350 0)× 10-6 cm/s,and is sensitive to the clay content;with an increase of clay content,the permeability coefficient decreases.Combined with the analysis of the composition and structure of the clay soil,the effective porosity ratio is calculated using an empirical equation and conventional geotechnical indices.Then,the permeability coefficient is found using a modified version of the Kozeny-Carman equation.The results show that the value of Kprediction/K measurement falls between 0.25 and 8.25.The reliability of the empirical equation derived and used to calculate the effective porosity ratio is verified by comparing its analytical predictions with measured data of clay soils at other locations in the area.The calculation formulas and methods presented in the paper can be used for reference in other areas.
coefficient of permeabilityclay soileffective porosity ratioLangfang subsidence areaempirical equation
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