Abstract: In order to clarify the clogging characteristics of geotextiles in iron tailings dam with high content of fine particles，and to find a more suitable type of geotextile for iron tailings dam，the permeabili⁃ ty test of the system composed of three kinds of geotextiles（short fiber，filament yarns and filter cloth） and an iron tailings slurry is carried out by improving the gradient ratio test. By analyzing the variation law of gradient ratio and system permeability coefficient，combined with the analysis of the variation law of par⁃ ticle migration in geotextile filter layer after the test，the mechanical clogging mechanism is revealed.At the same time，the chemical composition of the test soil samples is tested to reveal the chemical clogging mech⁃ anism.The results show that with the increase of hydraulic gradient，the geotextiles of short fiber and filter cloth show excellent reverse filtration performance，while the geotextiles of filament yarns show more seri⁃ ous clogging phenomenon.After the test，a good reverse filter layer is formed in the middle of the filter cloth geotextile filter layer. The chemical clogging is mainly caused by the oxidation reaction of Fe2+ in iron tailings to form Fe（OH）3 colloid.The conversion rate of Fe2+ to Fe3+ is in the order of short fiber> filament yarns > filter cloth. The filter cloth geotextile shows good resistance to chemical clogging and is more suit⁃ able for iron tailings dam project.

Key words: iron tailings, geotextiles, reverse filter, gradient ratio test, mechanical clogging, chemi? cal clogging