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Geotextiles—Test method for air permeability
1 Subject content and applicable scope
This standard specifies the determination method of geotextile permeability.
This standard is applicable to nonwoven geotextile, woven geotextile and knitted geotextile, but not to geomembrane.
2 Normative references
GB 6529 Textiles—Standard atmospheres for conditioning and testing
GB 8170 Rules for rounding off of numberical values
GB/T 13760 Geotextiles—Sampling and preparation of test specimens
3 Terms
3.1
air permeability
the permeability to air of geotextile with differential pressure on both sides.
3.2
air permeation volume
the volume of air flowing through the unit area per unit time under the specified pressure difference on both sides of the geotextile, in m3/m2·S.
4 Principle
According to the specified method and test parameters, make both sides of geotextile reach a certain pressure difference to measure the air permeation volume of geotextile.
5 Apparatus and appliances
5.1 A specimen clamping machine that capable of making the specimen not deformed and the edge not leak.
5.2 A fan that sucks air to make both sides of the geotextile reach the specified pressure difference.
5.3 Pressure gauge for measuring pressure difference.
5.4 Device for measuring air flow and a set of calibrated apertures, with the flow error not exceeding ±2%.
5.5 Calibration orifice plate used to calibrate the apparatus.
6 Standard atmosphere for conditioning and testing
The standard atmosphere shall be in accordance with Class III standard specified in GB 6529:
temperature: 20±2°C;
relative humidity: 65%±5%.
7 Sampling
Requirements for sampling in GB/T 13760 apply.
8 Preparation before test
8.1 Before the test, the sample shall be humidified for 24h under standard atmospheric conditions; or before the test, the sample shall be placed in the standard atmosphere to make the air flow smoothly through it until the weighing difference of the sample every 2h does not exceed 0.25%.
8.2 Cut the specimen from the sample. The dimension of the specimen may be determined according to the specific conditions of the test apparatus. The specimen shall not be wrinkled or ironed.
8.3 Number of tests
8.3.1 The number of tests may be obtained according to the coefficient of variation using the following Equation:
N＝0.154 CV2
where,
N——the number of tests (rounded up to the nearest integer).
CV——the coefficient of variation, %.
8.3.2 If the coefficient of variation of the tested fabric has not been determined, it cannot be directly calculated using the above equation, but a fixed number of tests N=15 may be used.
1 Subject content and applicable scope
2 Normative references
3 Terms
4 Principle
5 Apparatus and appliances
6 Standard atmosphere for conditioning and testing
7 Sampling
8 Preparation before test
9 Operating procedures
10 Result calculation
11 Test report
Annex A Schematic diagram of air permeation volume tester
