1、Designation: D 7406 07Standard Test Method forTime-Dependent (Creep) Deformation Under ConstantPressure for Geosynthetic Drainage Products1This standard is issued under the fixed designation D 7406; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method is used to determine the unconfinedcompressive creep characteristics of
3、drainage geotextiles, geo-composites, geonets, or any other geosynthetic associated withdrainage at a constant temperature, when subjected to aconstant compressive stress.1.2 This test method is intended for use as an unconfinedcompressive performance creep test only. For a detailedprocedure on how
4、to establish an index test see the EN standard1897. For performance tests, the specimen shall be subjected tothe site-specific liquid and/or the site-specific stress (normaland potentially shear stress).NOTE 1Results achieved from unconfined compressive performancecreep may differ from testing perfo
5、rmed under confined conditions.1.3 Because of the changing nature of the geosyntheticindustry, and the wide variety of products already available,this particular test method may have to be slightly modified forunconfined compression creep testing of some products1.4 The values given in SI units are
6、to be considered as thestandard. The values given in parentheses are for informationonly. This standard covers the specific procedures and testconditions that are applicable for exposure of unreinforcedpolyolefin geomembranes to fluorescent UV radiation andcondensation.1.5 This standard does not pur
7、port to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D
8、2990 Test Methods for Tensile, Compressive, and Flex-ural Creep and Creep-Rupture of PlasticsD 4439 Terminology for GeosyntheticsD 5199 Test Method for Measuring the Nominal Thicknessof GeosyntheticsD 5261 Test Method for Measuring Mass per Unit Area ofGeotextilesD 5262 Test Method for Evaluating th
9、e Unconfined TensionCreep and Creep Rupture Behavior of GeosyntheticsD 6364 Test Method for Determining Short-Term Compres-sion Behavior of Geosynthetics2.2 EN Standard:EN 18973. Terminology3.1 For definitions related to geosynthetics, see Terminol-ogy D 4439.3.2 For definitions related to creep, se
10、e Test MethodsD 2990 and D 5262.3.3 Definitions: ).3.3.1 compressive creep, ntime-dependent deformation orcompressive strain of a material subjected to a constantcompressive stress.3.3.2 compressive creep rupture, nfailure by collapse of amaterial subjected to a constant compressive stress.4. Summar
11、y of Test Method4.1 In this performance test method, a geosynthetic drain-age product is subjected to a sustained normal and potentiallyshear stresses. Deformations of the specimen are recorded atdesignated time intervals, and a graph is drawn.4.2 The specimen may be immersed in a site-specific wate
12、ror permeant, to simulate actual field conditions.4.3 3 For long-term testing it is recommended that the testbe run for at least 1000 h. Dwell times up to 10000 hr havebeen used, if that longer time data is required.4.4 Creep load (normal as well as potentially shear) shouldreflect the actual field
13、conditions4.5 The test will be conducted at site specific temperatures.1This test method is under the jurisdiction of ASTM Committee D35 onGeosynthetics and is the direct responsibility of Subcommittee D35.02 on Endur-ance Properties.Current edition approved Dec. 1, 2007. Published January 2008.2For
14、 referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700
15、, West Conshohocken, PA 19428-2959, United States.5. Significance and Use5.1 The performance characteristics of a drainage geosyn-thetic are directly related to the integrity under compressiveloading. If the product is sensitive to compressive creep, itsflow capacity could be greatly reduced or even
16、 shut offcompletely.5.2 The creep sensitivity of a candidate geosynthetic can betested at field-simulated normal stress and potentially shearstresses.5.3 This test method does not evaluate the effect of creep ofa geotextile filter or adjacent membrane.5.4 Compression creep as it relates to reduction
17、 in flowcapacity of a geosynthetic drainage product is manufacturerand product specific. For example, a 10% reduction in originalthickness of a geonet made by manufacturer A does notnecessarily equal the same reduction in flow capacity as a 10%reduction in thickness of the same or another type of ge
18、onetmade by manufacturer B.5.5 This creep data has is merit directly to the end user,because it can be easily interpreted to result into a reductionfactor for creep3. The Reduction factor can then be used toderive an allowable flow rate4.6. Apparatus6.1 Overall System Fig. 1 shows a compression cree
19、p testsetup. It consists of a loading platen, a normal stress assembly,potentially a shear load assembly (not shown in Fig. 1),potentially a specimen container, and three digital gages (oneshown in Fig. 1).6.2 Specimen Container The specimen container shallhave a flat, rigid surface on which the bas
20、e platen is placed.The container shall be deep enough to allow the test specimento be completely immersed during testing. The container shallbe large enough to hold a minimum specimen size of 150 by150 mm (6.0 by 6.0 in.), but can have size of 300 by 300 mm(12.0 by 12.0 in.) or larger to assure the
21、test setup remainsunconfined.6.3 Base Platen The base platen shall be rigid enough toresist bending and, in turn, support a uniform normal stress. Athick steel plate is advisable. The base platen shall be placed inthe specimen container to support the tested specimen. Whenshear stress is applied it
22、is necessary to avoid slippage of thetested specimen with the base platen (rough surfaces on theplaten are recommended). Ideally the base platen will be largerthan the specimen size to support the specimen during drapingand flexing under the stress assembly.6.4 Loading Platen The loading platen shal
23、l be rigidenough to resist bending and, in turn, apply a uniform normalstress. When shear stress is applied it is necessary to avoidslippage of the tested specimen with the loading platen (roughsurfaces on the platen are recommended). The loading platenshall be slightly larger than the specimen to p
24、rovide evencompression during the entire duration of the test. In additionthe loading platen will be attached to the stress assembly insuch a way that no stress is placed on the specimen until thecommencement of the test and the weight of which is includedin the measurement of the applied stress whe
25、n appropriate forthe loading system used.6.5 Digital GagesAt least 3 digital gages accurate to 0.01mm (0.0005 in.) shall be used to measure specimen deforma-tion for the normal stress assembly. Alternatively, any devicethat can measure deformations to an accuracy of 0.01 mm(0.0005 in.) may be substi
26、tuted for a digital gage (for example,a linear variable differential transformer (LVDT). If a shearstress assembly is used 1 digital gages shall be used to measurethat deformation.6.6 Normal Stress and Potentially Shear Stress Assem-blyThe compressive stress may be applied mechanically, pneu-matical
27、ly, or hydraulically. The loading device, however, shallbe capable of applying the full magnitude of test stress in onecontrolled step (with no significant impact). Some systems mayuse dead weights to apply stress. At high stress levels, themagnitude of the weight required may make it difficult orim
28、possible to load the system in a controlled manner. In this3Giroud, J.-P., Zhao, A. and Richardson, G. N. (2000), “Effect of ThicknessReduction on Geosynthetic Hydraulic Transmissivity,” Geosynthetics International,Vol. 7, Nos. 4-6, pp. 433-452.4GRI GC-8 standard (2001), “Standard guide for determin
29、ation of the allowableflow rate of a drainage geocomposite”FIG. 1 Creep Apparatus Cross SectionD7406072case, a hydraulic jack can be used to support the weights untilthe test is commenced.NOTE 2Given the large variety of shear stress assemblies in use, itwas not the intent to eliminate some units in
30、 use, by describing here onlysome. From movable platens, to inclined plates, to block assemblies havebeen used successfully to collect shear deformations and ultimately shearstrains. Key is to assure that the shear stress is transferred into thespecimen, hence extra care has to be taken to assure th
31、ere is no slippage.7. Sampling and Test Specs and Units7.1 Test Specimens- Remove at least two specimen normallytaken equally spaced across the laboratory sample. The speci-men shall be cut square, a minimum of 150 by 150 mm (6.0 by6.0 in.). The specimen shall be taken no less than 300 mm (12in.) fr
32、om the edge of the stock and shall be examined beforetesting to verify that it is representative of the stock from whichit is taken.NOTE 3Given that the compressive units described in this test methodhave sizes ranging from 150 mm to 300mm square, it is recommended thatthe largest size specimen is t
33、ested that will fit within the testing device. Inaddition for some very high stresses, the available pressure might limit thesize of the tested sample. However that minimum cannot be less than 150mm by 150mm.7.2 Test specimens that are to be immersed during testingshall be saturated in the site-spec
34、ific liquid or leachate at thetemperature desired by the end user until equilibrium isreached (typically within a tolerance of 6 0.5C for 24 hbefore testing).8. Conditioning8.1 Testing shall be conducted at the site specific tempera-ture 6 0.5C. If the laboratory cannot be controlled within thisrang
35、e, tests need to be performed in a suitable environmentalchamber capable of controlled cooling and heating. Theenvironmental chamber shall have a programmable or set-pointcontroller so as to maintain the desired temperature to 60.5C.8.2 Allow the specimen adequate time to come to tempera-ture equili
36、brium in the laboratory or environmental chamber.Generally, this can be accomplished within a few hours.8.3 Record the relative humidity in the laboratory or envi-ronmental chamber if moisture sensitive products are testedand are not immersed into the permeant.9. Procedure9.1 Place specimen to be te
37、sted onto the loading base. If thespecimen is to be immersed, it shall be done so during this stepand placed into a specimen container. 99.2 Insert the specimen container into Normal Stress-andpotentially shear stress assembly.9.3 Set the loading platen into position over the specimenand adjust the
38、dial over the loading platen. The 3 digital gaugesare positioned on 3 different sides of the loading platen. It isrecommended that the dial gauges are zeroed more or less atthe same time when the desired level of stress is applied to thespecimen.9.4 Reposition coupons horizontally once a week by (1)
39、moving the two extreme right hand coupon holders to the farleft of the exposure area, and (2) sliding the remaining couponholders to the right.9.5 Apply the desired level of stress (normal and potentiallyshear ).NOTE 4Loading in a stepwise fashion could be more representative tosimulate conditions i
40、n the field. If the applied stress was applied in astepwise fashion, it should be recorded in the report.9.6 Record deformation readings from the 3 digital gaugesfrom the normal stress assembly, potentially also from theshear stress assembly at 1, 10, 30, 60 min and 2, 4, 8, 24, 48,72, 96, 120, 144,
41、 and 168 h. Readings are taken at every 168h thereafter.9.7 Readings shall continue for a minimum of 168 h, up till1000 hrs or more if longer-term data are required. Dwell timesup to 10000 hrs have been used, but for some products evenlonger dwell times are recommended. 9.8 Repeat the procedure9.1 t
42、hrough 9.7 on the remaining test specimens.9.8 Repeat the procedure 9.19.8in the remaining testspecimens.FIG. 2 Typical Geocomposite Creep ResponseD740607310. Calculation10.1 Applied normal stress may be calculated as follows:sn= P/Awhere:sn= normal stress in kPa (psi),P. = applied vertical load in
43、kN (lbf), andA = planar area of specimen in m2(in.2)10.2 Applied shear stress may be calculated as follows: T =Fs/Awhere:Tn= shear stress in kPa (psi),Fs= applied shear load in kN (lbf), andA = planar area of specimen in m2(in.2)10.3 Normal strain may be calculated as follows: en=(Ln/Ln) 3 100where:
44、en= strain (%) for each digital gauge (n),n = digital gauge number,DLn= deformation in mm (in.), andLn= initial thickness in mm (in.).NOTE 5The initial thickness (for each location the digital gauge isplaced) is measured in the compressive creep unit with a normal stress of20kPa, before the desired
45、level of stress is applied.10.4 Shear strain may be calculated as follows: gs=(DH/Ln) x 100where:gs= shear strain (%),DH = horizontal displacement of one face platen relative tothe other in mm (in.), andLn= initial thickness in mm (in.).10.5 The specimen test result is the average of the 3 normalstr
46、ains measured from the 3 different normal digital gaugelocations; or potentially the average of the shear strainsmeasured from the different shear digital gauge locations10.6 The sample test results is the average of the specimentest results, normal and potentially shear, respectfully.11. Report11.1
47、 The report shall include a description of the materialtested including its short-term compressive behavior per TestMethod D 6364, thickness per Test Method D 5199 at 20kPa,mass per unit area per Test Method D 5261, applied normalstress, potentially a shear stress. The conditions under whichthe test
48、 was conducted (temperature, site specific liquid if any)including conditioning of the specimens, shall also be reported.11.2 The report shall include a plot of the average normalstrain versus time for each specimen tested, if a shear stresswas applied that shear strain versus time should be plotted
49、 aswell. Fig. 2 shows a typical normal stress response for a singlespecimen of geocomposite.11.3 The report shall include a table showing for all timessteps data was collected per specimen tested: normal deforma-tions in mm collected for each digital gauge, calculated normalstrain for each digital gauge, in addition the average normalstrain for all digital gauges collecting the normal deformation.If a shear stress was applied, shear deformation, and shearstrain versus time as well.11.4 f it is desired to extrapolate creep response to futuretimes, there are a number of
