geotextile aos selection - chesapeake, virginia on the sieve analysis of the material to be retained...
TRANSCRIPT
CALCULATIONS
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This analysis is to determine the appropriate maximum Apparent Opening Size (AOS) for the geotextile component of the proposed leachate collection system.
1.0 ASSUMPTIONS
� The gravel drainage layer material consists of gravel corresponding to the gradation specification of the Virginia Department of Transportation (VDOT) #57 stone; and,
� The stone has a carbonate content of less than 15%.
2.0 CALCULATIONS
2.1 AOS
Choice of apparent opening size (AOS) of a geotextile can be made using a variety of methods (Reference 2, Chapter 8). Since the purpose of the geotextile is to provide separation, the methods are based on the sieve analysis of the material to be retained (fly ash). A representative sample gradation analysis (sample ID# DPYT-SF-12) of fly ash from a similar project will be used for the AOS determination.
2.1.1 Task Force 25 Method
Examine the percentage of soil passing the #200 sieve, then select AOS based on the following recommendations:
Particles < 50% passing #200 sieve, AOS of the fabric > #30 sieve, or
Particles > 50% passing #200 sieve, AOS of the fabric > #50 sieve.
For sample DPYT-SF-12, the % passing the #200 sieve is 77.6%. Per the TF 25 method, select AOS as #50 sieve.
2.1.2 Giroud Method
Based on the CU (coefficient of uniformity) criteria of the soil a flowchart for soil retention criteria under steady state flow conditions has been developed (Chart 1 from Reference 3).
The path through the flowchart is illustrated on the attached Chart 1. From this, the minimum AOS selection is the #200 sieve.
The more restrictive of these methods (Giroud) yields a minimum AOS of #200 sieve. Typical AOS of manufactured nonwoven geotextiles is no smaller than the #100 sieve. To compensate for the sieve size, a thick (heavier weight) geotextile is recommended to improve its filtration capacity.
Date: August 29, 2013 Made by: DPM
Project No.: 130-0193 Checked by: ATN
Subject: Geotextile AOS Calculations Reviewed by: JRD
Project: CHESAPEAKE ENERGY CENTER ASH LANDFILL - SWP #440
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Geotextile AOS Calculations August 29, 2013 CEC Ash Landfill – SWP #440 2 130-0193
3.0 REFERENCES
1. Koerner, Robert M., Designing with Geosynthetics, Fifth Edition, 2005 2. Qian, Xuede, Koerner, Robert M., and Gray, Donald H, Geotechnical Aspects of Landfill Design and Construction, 2002. 3. Ten Cate Nicolon Corporation, Geotextile Filter Design, Application, and Product Selection Guide, 2002.
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