Hydraulic and Chemical Stability of Polypropylene Geotextile Filters in Saline Soil: Results from a Three-Stage Field Study

Abstract

Arezoo Salamatnia*, Hamzeh Saeedi and Mehrdad Nahavandchi

The Polypropylene geotextile filters are increasingly used in subsurface irrigation and drainage systems because of their cost-effectiveness and superior hydraulic performance compared to conventional gravel filters. This study evaluated the permeability and durability of these filters under saline soil conditions in Khuzestan Province, Iran. A three-stage field investigation assessed short-term (0–1 year), medium- term (5–10 years), and long-term (more than 20 years) performance. Samples were collected from three farms Mirza Kouchak Khan, Nakhil at Abadan Khorramshahr, and Salman Farsi and tested according to the Netherlands Standard NEN 7090 (KOMO method). The tested polypropylene filters had mean pore size ranges of 355–500 micrometers (type PP450) and 600–850 micrometers (type PP700). The short and medium term PP450 filters met the performance criteria of more than 10 percent particle passage through the finer screen and less than 10 per cent through the coarser screen, while the long term PP450 samples showed slightly higher permeability values. The medium-term PP700 sample initially failed but passed upon retesting, and the long term PP700 filters met the permeability limits at the 600–850 micrometer range. Soil analyses indicated an electrical conductivity of up to 2.5 deci Siemens per meter, a sodium adsorption ratio of up to 4.5, and elevated ion and iron concentrations. No chemical degradation or structural damage of the polypropylene fibers was detected, and minor permeability reductions were attributed to mechanical clogging by fine sediments. Overall, the results confirm that polypropylene geotextile filters maintain high hydraulic stability and chemical resistance for at least 20 to 25 years, making them a technically and economically sustainable solution for saline, fine-textured soils.

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