Abstract:It is very important to analyze the effect of leachate on permeability properties of geosynthetic clay liner(GCL) when GCL is used as the liner of landfill. To overcome the shortcomings in seepage test such as weak repeatability and time-consumption,the saturated permeability coefficient of GCL is studied in a microscopic angle. Firstly,change law of intraparticle void ratio with CaCl2 concentration is found based on the current knowledge about microstructure of bentonite and the results from SEM method. Secondly,taking bentonite as dual porous media,calculation formula of the distance between layers of gel-type montmorillonite in interparticle pores, ,is deduced. Finally,improved calculation method of permeability coefficient is derived using and Poiseuille law. The method can take the effect of the changes of CaCl2 concentration and void ratio on permeability coefficient into account. And the comparison of calculated and measured permeability coefficient validates the method. It is shown that the changes of is resulted from the changes of both apparent porosity and the distance between layers of gel-type montmorillonite in interparticle pores.