Since water permeability determination of geotextiles is mostly carried out at ambient temperature and not at the reference temperature, a correction factor based on the ratio of the viscosity of water at ambient test temperature and that at the reference temperature is considered. This correction factor was assumed for all flow conditions although, strictly, it only applies to laminar flow. Since the flow of water through most geotextiles does not occur under laminar conditions, the applied correction results in incorrect values of permeability. Permeability determinations of geotextiles illustrate that temperature correction for flow conditions, other than laminar, may result in a much larger deviation than no correction. A possible solution for the problem is the determination of water permeability within narrow limits around the reference temperature. This will undoubtedly require additional equipment. Experiments to detect the influence of the temperature have therefore been carried out and a procedure to correct water permeability values of geotextiles towards a reference temperature has been proposed. This correction holds for both the quadratic flow equation and the exponential equation, and is based on the application of the correction factor for the laminar part of the applied flow equation. The paper describes the experimental set-up and the results obtained, and gives evidence of the improved results if corrections are made according to the proposed procedure.
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