The chemical clogging of geotextiles filters is a common issue, which threatens the safety of engineering projects. To reduce the chemical clogging of nonwoven geotextiles and enhance their drainage capability, a polyurethane foam was innovatively placed under the nonwoven geotextiles in this paper. A series of column tests were conducted to study the mechanism of the polyurethane foam to reduce the chemical clogging of the nonwoven geotextile filters in tailings caused by ferrous iron. In addition, the influence of the concentration of Fe2+, hydraulic gradient and thickness of the tailings specimen on the chemical clogging of the polyurethane foam and nonwoven geotextiles was examined. Less chemical clogging of geotextiles caused by polyurethane foam was observed and the related mechanism was firstly explained. The polyurethane foam under the geotextile reduced the contact between the geotextile and air. As a result, the chemical clogging of the geotextile was alleviated, which increased the drainage capability of the geotextiles. A high water saturation of the polyurethane foam would help to a reduce the extent of the chemical clogging of the geotextile. The chemical clogging characteristics of geotextiles and polyurethane foam under different concentrations of Fe2+ and hydraulic gradients were observed.

Nonwoven geotextiles are widely used in tailings ponds for filtration and drainage, but there is a risk of failure of nonwoven geotextile due to physical clogging. In this study, to reduce the clogging of nonwoven geotextile filter in tailings ponds and improve its long-term drainage performance, a layer of woven geotextile is placed between tailings and nonwoven geotextile to form a composite filter of woven-nonwoven geotextile. A series of gradient ratio tests were conducted to study the influence of the aperture of woven geotextile on the filtration characteristics of composite filter. The long-term filtration performance of composite filter was evaluated, and the filtration mechanism of composite filter was revealed. The results show that after adding a layer of woven geotextile with reasonable aperture upon the nonwoven geotextile, the gradient ratio of filter decreased and the flow rate of filter significantly increased. The filtration performance of composite filter of geotextile was better than that of nonwoven geotextile filter. The aperture of woven geotextile had an important influence on the filtration characteristics of composite filter. With the increase of the aperture of woven geotextile, the gradient ratio value of the composite filter decreased first and then increased. For relatively dense tailings, the recommended ratio of the equivalent aperture of woven geotextile (O95) to the characteristic particle diameter of tailings (d85) s is about 1.6.