1、Standard Practice for Determination of Long-Term Strength for Geosynthetic Reinforcement AASHTO Designation: R 69-151American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-4e R 69-1 AASHTO Standard Practice for Determinat
2、ion of Long-Term Strength for Geosynthetic Reinforcement AASHTO Designation: R 69-151INTRODUCTION Through this protocol, the long-term strength and stiffness of geosynthetic reinforcements can be determined. This protocol contains test and evaluation procedures to determine reduction factors for ins
3、tallation damage, creep, and chemical/biological durability, as well as the method to combine these factors to determine the long-term strength. The long-term strength and stiffness values determined from this protocol can be used as input values for geosynthetic structure designs conducted in accor
4、dance with AASHTO LRFD Bridge Design Specifications and related Federal Highway Administration (FHWA) design guidelines. The long-term strength and stiffness values determined from this protocol can also be compared to the required design strength and stiffness values provided in the contract for th
5、e geosynthetic structure(s) in question to determine whether the selected product meets the contract requirements. This protocol can be used for product qualification or acceptance (e.g., for inclusion in a Qualified Products List), or for verification to facilitate periodic review of products for w
6、hich the long-term strength has been previously determined using this standard practice. 1. SCOPE 1.1. This protocol has been developed to address polypropylene (PP), polyethylene (PE or HDPE), and polyester (PET) geosynthetics (i.e., geotextiles and geogrids). For other geosynthetic polymers (e.g.,
7、 polyamide (PA) or polyvinyl alcohol (PVA), the installation damage and creep protocols provided herein are directly applicable. While the chemical and biological durability procedures and criteria provided herein may also be applicable to other polymers (for example, hydrolysis testing as described
8、 in Annex C is likely applicable to PA and PVA geosynthetics), additional investigation will be required to establish a detailed protocol and acceptance criteria for these other polymers. These other polymers may be considered for evaluation using this protocol once modifications to the chemical/bio
9、logical durability aspects of this protocol have been developed and are agreed upon by the approval authority. 1.2. The values stated in SI units are to be regarded as the standard. 1.3. This standard may involve hazardous materials, operations, and equipment. This standard does not propose to addre
10、ss all safety problems associated with its usage. It is the duty and responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2015 by the American Association of State Highway and Transpor
11、tation Officials.All rights reserved. Duplication is a violation of applicable law.TS-4e R 69-2 AASHTO 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards and Specifications: T 96, Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine AASHTO LRFD Bridge
12、 Design Specifications Standard Specifications for Highway Bridges, 17th Edition 2.2. ASTM Standards: D1248, Standard Specification for Polyethylene Plastics Extrusion Materials for Wire and Cable D2488, Standard Practice for Description and Identification of Soils (Visual-Manual Procedure) D2837, S
13、tandard Test Method for Obtaining Hydrostatic Design Basis for Thermoplastic Pipe Materials or Pressure Design Basis for Thermoplastic Pipe Products D3045, Standard Practice for Heat Aging of Plastics Without Load D3083-89, Specification for Flexible Poly (Vinyl Chloride) Plastic Sheeting for Pond,
14、Canal, and Reservoir Lining (Withdrawn 1998) D3895, Standard Test Method for Oxidative-Induction Time of Polyolefins by Differential Scanning Calorimetry D4101, Standard Specification for Polypropylene Injection and Extrusion Materials D4355/D4355M, Standard Test Method for Deterioration of Geotexti
15、les by Exposure to Light, Moisture and Heat in a Xenon Arc Type Apparatus D4595, Standard Test Method for Tensile Properties of Geotextiles by the Wide-Width Strip Method D4603, Standard Test Method for Determining Inherent Viscosity of Poly(Ethylene Terephthalate) (PET) by Glass Capillary Viscomete
16、r D5261, Standard Test Method for Measuring Mass per Unit Area of Geotextiles D5262, Standard Test Method for Evaluating the Unconfined Tension Creep and Creep Rupture Behavior of Geosynthetics D5322, Standard Practice for Immersion Procedures for Evaluating the Chemical Resistance of Geosynthetics
17、to Liquids D5818, Standard Practice for Exposure and Retrieval of Samples to Evaluate Installation Damage of Geosynthetics D5885, Standard Test Method for Oxidative Induction Time of Polyolefin Geosynthetics by High-Pressure Differential Scanning Calorimetry D6637, Standard Test Method for Determini
18、ng Tensile Properties of Geogrids by the Single or Multi-Rib Tensile Method D6992, Standard Test Method for Accelerated Tensile Creep and Creep-Rupture of Geosynthetic Materials Based on Time-Temperature Superposition Using the Stepped Isothermal Method D7409, Standard Test Method for Carboxyl End G
19、roup Content of Polyethylene Terephthalate (PET) Yarns 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-4e R 69-3 AASHTO 2.3. Other Standards: ISO 13438:2004(en), Geotextiles and geotextile-related pro
20、ductsScreening test method for determining the resistance to oxidation GRI-GG8, Determination of the Number Average Molecular Weight of PET Yarns Based on a Relative Viscosity Value ISO 10319:2008, GeosyntheticsWide-width tensile test ISO/DIS 10722:2007, GeosyntheticsIndex test procedure for sthe ev
21、aluation of mechanical damage under repeated loading. Part 1: Installation in granular materials ISO/FDIS 9080:2012, Plastic piping and ducting systemsDetermination of long-term hydrostatic strength of thermoplastics materials in pipe form by extrapolation 3. TERMINOLOGY 3.1. aperturesthe open space
22、s formed between the interconnected network of longitudinal and transverse ribs of a geogrid. 3.2. d50 the grain size at 50 percent passing by weight for the backfill. 3.3. effective design temperaturethe temperature that is halfway between the average yearly air temperature and the normal daily air
23、 temperature for the warmest month at the geosynthetic structure site. 3.4. HDPEhigh-density polyethylene. 3.5. hydrolysisthe reaction of water molecules with the polymer material, resulting in polymer chain scission, reduced molecular weight, and strength loss. 3.6. in-isolation testinggeosynthetic
24、 testing in which the specimen is surrounded by air or a fluid (not soil). 3.7. installation damagedamage to the geosynthetic, such as cuts, holes (geotextiles only), abrasion, fraying, etc., created during installation of the geosynthetic in the backfill soil. 3.8. load levelfor creep or creep-rupt
25、ure testing, the load applied to the test specimen divided by Tlot, the short-term ultimate strength of the lot or roll of material used to form the creep testing. 3.9. MARVthe minimum average roll value for the geosynthetic, defined as two standard deviations below the mean for the product (i.e., 9
26、7.5 percent of all test results will meet or exceed the MARV). For practical purposes, from the users viewpoint, the average for a sample taken from any roll in the lot shipped to the job site should meet or exceed the MARV. 3.10. minimum valuethe lowest sample value from documented manufacturing qu
27、ality control test results for a defined population from one test method associated with one specific property. 3.11. MSEmechanically stabilized earth. 3.12. nonaggressive environmentfor geosynthetic walls and slopes, soils that have a d50of 4.75 mm or less, a maximum particle size of 31.5 mm or les
28、s, a pH of 4.5 to 9, and an effective design temperature of 30C (85F) or less. 3.13. oxidationthe reaction of oxygen with the polymer material, initiated by heat, UV radiation, and possibly other agents, resulting in chain scission and strength loss. 2015 by the American Association of State Highway
29、 and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-4e R 69-4 AASHTO 3.14. PETpolyester. 3.15. postconsumer recycled materialpolymer products sold to consumers that have been returned by the consumer after use of the products for the purpose of recyclin
30、g. 3.16. PPpolypropylene. 3.17. primary and secondary productsfor product line characterization purposes, the primary product is the product in which the full suite of index and performance level tests are conducted to characterize the product line, whereas the secondary products are those used to c
31、haracterize the consistency of the properties throughout the range of products included in the line (or to facilitate the interpolation of those properties to products in the line not specifically tested) using a limited suite of index and performance level tests. 3.18. product linea series of produ
32、cts manufactured using the same polymer (including stabilizers) in which the polymer for all products in the line comes from the same source and/or is purchased or manufactured by the geosynthetic manufacturer using the same property and material specifications for the base polymer plus additives, t
33、he manufacturing process is the same for all products in the line, and the only difference is in the product weight/unit area or number of fibers contained in each reinforcement element. 3.19. product qualification testingtesting used to establish the acceptability of the product or product line by
34、an agency prior to shipment or use of the product in a specific project (e.g., as the basis for adding the product to the agencys qualified or approved products list). 3.20. product verification testingtesting used to verify that the product or product line has not changed since being tested for pro
35、duct qualification (e.g., as the basis for allowing the product or product line to remain on the agencys qualified or approved products list). 3.21. QPLqualified products list. 3.22. RFcombined reduction factor to account for long-term degradation due to installation damage, creep, and chemical/biol
36、ogical aging. 3.23. RFCR strength reduction factor to prevent long-term creep rupture of the reinforcement. 3.24. RFDstrength reduction factor to prevent rupture of the reinforcement due to long-term chemical and biological degradation. 3.25. RFIDstrength reduction factor to account for installation
37、 damage to the reinforcement. 3.26. samplea portion of material that is taken for testing or for record purposes, from which a group of specimens can be obtained to provide information that can be used for making statistical inferences about the population(s) from which the specimens are drawn. 3.27
38、. specimena specific portion of a material or laboratory sample upon which a test is performed or that is taken for that purpose. 3.28. survivabilitythe ability of a geosynthetic to survive a given set of installation conditions with an acceptable level of damage. 3.29. Tal the long-term tensile str
39、ength that will not result in rupture of the reinforcement during the required design life, calculated on a load per unit of reinforcement width basis. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-
40、4e R 69-5 AASHTO 3.30. Tultthe ultimate tensile strength of the reinforcement determined from wide-width tensile tests. 3.31. UVultraviolet light. 4. SIGNIFICANCE AND USE 4.1. This recommended practice provides a protocol to assess the reduction in tensile strength and stiffness of geosynthetic (i.e
41、., geotextiles and geogrids) reinforcement that occurs due to the installation of the material in or immediately beneath soil backfill and due to time exposure to the ambient environment (e.g., temperature, pH, oxygen, water, or other materials or chemicals in the surrounding environment) during the
42、 design life for the structure. This recommended practice is applicable to the assessment of these long-term properties for individual geosynthetic reinforcement products as well as for geosynthetic reinforcement product lines. This reduced strength can be used as a design value in the design of geo
43、synthetic reinforced structures such as walls, reinforced slopes, or embankment base reinforcement, or can be used for material acceptance and verification purposes for the construction of such structures. 4.2. Due to the length of time required to obtain the test data required, this recommended pra
44、ctice is generally not practical to be carried out on a suite of products for a specific project. Its primary use is to establish values that can be used at a program level by an agency or the geosynthetic manufacturer, using data developed for a range of site conditions likely to be encountered tha
45、t can be adapted to the site-specific conditions encountered in specific construction projects as needed. 4.3. This practice has not been developed to establish strength and stiffness properties directly applicable to dynamic loading situations, such as in pavement base course reinforcement. The str
46、ength and stiffness properties obtained using this practice have been shown to be applicable to seismic loading situations, though the values obtained are likely to be conservative in that case, at least with regard to creep. 5. EVALUATION OF SOIL ENVIRONMENT AGGRESSIVENESS EFFECTS ON LONG-TERM STRE
47、NGTH DETERMINATION 5.1. The assessment of geosynthetic long-term strength depends on the aggressiveness of the environment to which it will be subjected. The protocols provided generally address what are defined as non-aggressive environments, except where noted. The aggressiveness of the environmen
48、t with regards to geosynthetic long-term strength determination shall be based on soil gradation and particle characteristics of the backfill soil, chemical properties of the backfill soil and adjacent environment, and site temperature. Soil gradation and particle characteristics primarily affect po
49、tential RFIDvalues, chemical properties affect the potential for high RFDvalues, and temperature affects potential for high RFDand high RFCRvalues. In general, the more angular the soil, the more uniform its gradation, the greater the maximum particle size, and the more durable the particles, the more aggressive the soil is with regard to potential for installation damage. While installation damage can be evaluated for a wide range of soil gradation and characteristics, it is generally undesir
