This standard specifies the method for determining the pore size of geotextiles by dry sieving method. This standard is applicable to non-woven geotextiles, woven geotextiles and knitted geotextiles processed by needle punching and bonding methods. GB/T 14799-1993 Geotextile pore size determination method Dry sieving method GB/T14799-1993 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Method for Determining Apparent Opening Size of a Geotextile by Dry Sieving
Geotextiles --- Determining Apparent Opening Size of a Geotextile by Dry Sieving Subject Content and Scope of Application
This standard specifies the method for determining the aperture of geotextile by dry sieving. GB/T 14799-93
This standard applies to nonwoven geotextiles, woven geotextiles and knitted geotextiles processed by needle punching and bonding. 2 Reference Standards
GB8170 Numerical Rounding Rules
3 Terminology
3.1 Aperture
The aperture of geotextile is expressed as the diameter of glass beads or spherical sand particles passing through it. 3.2 Effective Aperture (0.)
The effective aperture (0.) indicates the maximum particle diameter that can effectively pass through the geotextile, for example, 0. indicates that 90% of the apertures in the geotextile are lower than this value.
4 Principle
Use the geotextile sample as the sieve cloth, place glass beads of known diameter on the surface of the geotextile and vibrate the sieve, weigh the weight of the glass beads passing through the geotextile, calculate the sieving rate, replace glass beads of different diameters for testing, and thus draw the pore size distribution curve of the geotextile and calculate the O value. 5 Instruments and tools
5.1 Sieve diameter 200mm.
5.2 Standard sieve vibrating machine
Shaking times: 221 times/min, vibration times: 147 times/min, turning radius: 12.5mm.
5.3 Preparation of standard granular materials
Use the sieving method to prepare graded granules from washed and dried glass beads. The grades are as follows: 0.05~~0.071, 0.071~0.09, 0.09~0.125, 0.125~0.154, 0.154~0.18, 0.18~0.25, 0.25~0.28, 0.28~0.35, 0.35~0.45 (mm). 5.4 Soft brush.
5.5 Balance, weighing 200g, sensitivity 0.01g. 5.6 Stopwatch.
6 Sample preparation
Cut the sample 10 cm from the edge of the geotextile and 1 m from the end of the geotextile in the length direction of the roll. There should be no obvious holes on the sample, and avoid more than two samples in the same longitudinal or transverse position. Cut 5 samples, the sample diameter should be larger than the sieve diameter. Note: 1) If it is a needle-punched nonwoven geotextile, the number of samples is 5×n, n is the number of groups of selected particle sizes. 7 Test steps
7.1 Weigh 50g of the coarse particle size glass beads that have been graded, and then evenly spread them on the surface of the geotextile. 7.2 Clamp the sieve frame, sample and receiving tray on the vibrating sieve machine, start the machine, and shake the sample for 20 minutes. 7.3 After shutting down, weigh the glass beads that pass through the sample and record the weight, then brush off the glass beads on the surface of the sample with a brush. 7.4 Repeat the procedures specified in 7.1 to 7.3 on the same sample with the next group of finer glass beads until the screening rate is not less than that of the three-level continuous classification standard particles, and one group of glass beads has about 95% passing through the sample within the 20-minute sieving time. Note: 1) Needle-punched nonwoven geotextiles should be replaced with new samples. 7.5 Repeat the procedures specified in 7.1 to 7.4 for the remaining samples. 8 Result calculation
8.1 Screening rate can be calculated as follows
Where: B
Screening rate of glass beads passing through the sample, %;
-The average number of the same group of particle sizes that pass through the sieve for each sample, name, T——The amount of glass beads used in each test, g. Calculate to three decimal places and round to two decimal places according to GB8170. 8.2 Plot the lower limit of the particle size of each group of glass beads on the abscissa (logarithmic coordinate) of the semi-logarithmic coordinate paper, and the corresponding screening rate on the ordinate, and the pore size (Og.) at which 90% of the glass beads remain on the geotextile can be obtained. If other "O\ values ​​are required, indicate them in the test report. 9 Test report
Specimen name, specifications,
Test results (pore size distribution curve and 09 value), test atmospheric conditions;
Test date,
Circumstances that should be noted in the test;
Various deviations from this standard.
Drawing of A1 curve
GB/T14799-93
Appendix A
Drawing of pore size distribution curve of geotextile
(reference)
Drawing with the lower limit of the particle size of each group of glass beads as the abscissa and the average value of the screening rate as the ordinate. Aperture distribution curve. 100
A20 value determinationwwW.bzxz.Net
Aperture 0, mm
Figure A1 Aperture distribution curve
0% means that 90% of the glass beads remain on the geotextile, and its screening rate (B) is 1-90%=10%. The horizontal coordinate corresponding to the point with a vertical coordinate of 10% on the curve is defined as the effective aperture 0o, in mm. Additional notes:
This standard is under the jurisdiction of the Standardization Research Institute of the China Textile Industry Association. This standard was drafted by the Shanghai Textile Science Research Institute and the Standardization Research Institute of the China Textile Industry Association. The main drafters of this standard are Mai Jiajun, Wang Fenjuan, Chen Jie, Guan Zeqing, Wei Hong, and Xu Jian. 120
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