1、Designation: D7556 10Standard Test Methods forDetermining Small-Strain Tensile Properties of Geogrids andGeotextiles by In-Air Cyclic Tension Tests1This standard is issued under the fixed designation D7556; the number immediately following the designation indicates the year oforiginal adoption or, i
2、n the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover the determination of small-strain tensile properties of g
3、eogrids and geotextiles by subject-ing wide-width specimens to cyclic tensile loading.1.2 These test methods (A, B, and C) allow for the deter-mination of small-strain cyclic tensile modulus by the mea-surement of cyclic tensile load and elongation.1.3 This test method is intended to provide propert
4、ies fordesign. The test method was developed for mechanistic-empirical pavement design methods requiring input of thereinforcement tensile modulus. The use of cyclic modulus fromthis test method for other applications involving cyclic loadingshould be evaluated on a case-by-case basis.1.4 Three test
5、 methods (A, B, and C) are provided todetermine small-strain cyclic tensile modulus on geogrids andgeotextiles.1.4.1 Test Method ATesting a relatively wide specimen ofgeogrid in cyclic tension in kN/m (lbf/ft).1.4.2 Test Method BTesting multiple layers of a relativelywide specimen of geogrid in cycl
6、ic tension in kN/m (lbf/ft).1.4.3 Test Method CTesting a relatively wide specimen ofgeotextile in cyclic tension in kN/m (lbf/ft).1.5 The values stated in SI units are to be regarded asstandard. The values given in parentheses are provided forinformation only and are not considered standard.1.6 This
7、 standard does not purport 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 Documents
8、2.1 ASTM Standards:2D76 Specification for Tensile Testing Machines for TextilesD123 Terminology Relating to TextilesD579 Specification for Greige Woven Glass FabricsD4354 Practice for Sampling of Geosynthetics for TestingD4439 Terminology for Geosynthetics3. Terminology3.1 Definitions:3.1.1 atmosphe
9、re for testing geosynthetics, nair main-tained at a relative humidity of 50 to 70 % and a temperatureof 21 6 2C (70 6 4F).3.1.2 corresponding force, nsynonym for force at speci-fied elongation.3.1.3 force at specified elongation (FASE), nforce associ-ated with a specific elongation on the force-elon
10、gation curve.(Synonym for corresponding force.)3.1.4 force-elongation curve, nin a tensile test, graphicalrepresentation of the relationship between the magnitude of anexternally applied force and the change in length of thespecimen in the direction of the applied force. (Synonym forstress-strain cu
11、rve.)3.1.5 geogrid, ngeosynthetic formed by a regular networkof integrally connected elements with apertures greater than6.35 mm (14 in.) to allow interlocking with surrounding soil,rock, earth, and other surrounding materials to primarilyfunction as reinforcement.3.1.6 geosynthetic, nproduct manufa
12、ctured from poly-meric material used with soil, rock, earth, or other geotechnicalengineering related material as an integral part of a man madeproject, structure, or system.3.1.7 geotextile, nany permeable textile material usedwith foundation, soil, rock, earth, or any other geotechnicalengineering
13、 related material, as an integral part of a man-madeproject, structure, or system.3.1.8 integral, adjin geosynthetics, forming a necessarypart of the whole; a constituent.3.1.9 junction, npoint where geogrid ribs are intercon-nected to provide structure and dimensional stability.3.1.10 rib, nfor geo
14、grids, continuous elements of a geo-grid which are either in the machine or cross-machine directionas manufactured.3.1.11 tensile, adjcapable of tensions, or relating to ten-sion of a material.1These test methods are under the jurisdiction of ASTM Committee D35 onGeosynthetics and are the direct res
15、ponsibility of Subcommittee D35.01 onMechanical Properties.Current edition approved Feb. 1, 2010. Published April 2010. DOI:10.520/D755610.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume
16、 information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.12 tensile strength, (af), nfor geogrids, maximumresistance to deformation developed for a specific mat
17、erialwhen subjected to tension by an external force. Tensile strengthof geogrids is the characteristic of a sample as distinct from aspecimen and is expressed in force per unit width.3.1.13 tensile test, nfor geosynthetics, test in which amaterial is stretched uniaxially to determine the force elong
18、a-tion characteristics, the breaking force, or the breaking elon-gation.3.1.14 tension, nforce that produces a specified elonga-tion.3.2 For definitions of other terms used in these test methods,refer to Terminology D123 and D4439.4. Summary of Test Method4.1 Test Method AIn this test method, a rela
19、tively widegeogrid specimen is gripped across its entire width in theclamps of a constant rate of extension type tensile testingmachine operated at a prescribed rate of extension, applying auniaxial cyclic load to the specimen over specified limits ofcyclic axial strain and centered around six succe
20、ssively greaterlevels of prescribed or permanent axial strain. Tensile modulusin kN/m (lbf/ft) of the test specimen can be calculated at eachlevel of prescribed axial strain from the last cycles of load frommachine scales, dials, recording charts, or an interfaced com-puter.4.2 Test Method BA relati
21、vely wide, multiple layeredgeogrid specimen is gripped across its entire width in theclamps of a constant rate of extension type tensile testingmachine operated at a prescribed rate of extension, applying auniaxial cyclic load to the specimen over specified limits ofcyclic axial strain and centered
22、around six successively greaterlevels of prescribed or permanent axial strain. Tensile modulusin kN/m (lbf/ft) of the test specimen can be calculated at eachlevel of prescribed axial strain from the last cycles of load frommachine scales, dials, recording charts, or an interfaced com-puter.4.3 Test
23、Method CA relatively wide geotextile specimenis gripped across its entire width in the clamps of a constantrate of extension type tensile testing machine operated at aprescribed rate of extension, applying a uniaxial cyclic load tothe specimen over specified limits of cyclic axial strain andcentered
24、 around six successively greater levels of prescribed orpermanent axial strain. Tensile modulus in kN/m (lbf/ft) of thetest specimen can be calculated at each level of prescribed axialstrain from the last cycles of load from machine scales, dials,recording charts, or an interfaced computer.5. Signif
25、icance and Use5.1 Test MethodsA, B, and C provide a means of evaluatingthe tensile modulus of geogrids and geotextiles for applicationsinvolving small-strain cyclic loading. The test methods allowfor the determination of cyclic tensile modulus at differentlevels of prescribed or permanent strain, th
26、ereby accounting forpossible changes in cyclic tensile modulus with increasingpermanent strain in the material. These test methods shall beused for research testing and to define properties for use inspecific design methods.5.2 In cases of dispute arising from differences in reportedtest results whe
27、n using these test methods for acceptancetesting of commercial shipments, the purchaser and suppliershould conduct comparative tests to determine if there is astatistical bias between their laboratories. Competent statisticalassistance is recommended for the investigation of bias. As aminimum, the t
28、wo parties should take a group of test speci-mens which are as homogeneous as possible and which arefrom a lot of material of the type in question. The testspecimens should then be randomly assigned in equal numbersto each laboratory for testing. The average results from the twolaboratories should b
29、e compared using Students t-test forunpaired data and an acceptable probability level chosen by thetwo parties before the testing began. If a bias is found, either itscause shall be found and corrected or the purchaser andsupplier shall agree to interpret future test results in light of theknown bia
30、s.5.3 All geogrids can be tested by Test Methods A or B.Some modification of techniques may be necessary for a givengeogrid depending upon its physical make-up. Special adapta-tions may be necessary with strong geogrids, multiple layeredgeogrids, or geogrids that tend to slip in the clamps or thosew
31、hich tend to be damaged by the clamps.5.4 Most geotextiles can be tested by Test Method C. Somemodification of clamping techniques may be necessary for agiven geotextile depending upon its structure. Special clamp-ing adaptations may be necessary with strong geotextiles orgeotextiles made from glass
32、 fibers to prevent them fromslipping in the clamps or being damaged as a result of beinggripped in the clamps.5.5 These test methods are applicable for testing geotextileseither dry or wet. It is used with a constant rate of extensiontype tension apparatus.5.6 These test methods may not be suited fo
33、r geogrids andgeotextiles that exhibit strengths approximately 100 kN/m(600 lbf/in.) due to clamping and equipment limitations. Inthose cases, 100 mm (4 in.) width specimens may be substi-tuted for 200 mm (8 in.) width specimens.6. Apparatus6.1 Testing ClampsThe clamps shall be sufficiently wideto g
34、rip the entire width of the specimen and with appropriateclamping power to prevent slipping or crushing (damage).Fixed clamps shall be used.6.1.1 Size of Jaw FacesEach clamp shall have jaw facesmeasuring wider than the width of the specimen.6.2 Tensile Testing MachineA testing machine of theconstant
35、 rate of extension type as described in SpecificationD76 shall be used. The testing machine shall be capable ofapplying cyclic loads between specified limits of deformationas specified in 10.4 and 10.6. The machine shall be equippedwith a device for recording the tensile force and the amount ofsepar
36、ation of the grips. Both of these measuring systems shallbe accurate to 61.0 % and, preferably, shall be external to thetesting machine. The rate of separation shall be uniform andcapable of adjustment within the range of the test. A stroke ofapproximately 100 to 150 mm (4 to 6 in.) and a load ratin
37、g ofapproximately 50 kN (11 kips) is recommended for these typesof tests.D7556 1026.3 Distilled Water and Nonionic Wetting AgentUsed forwet specimens only.6.4 ExtensometerWhen required by the test method, adevice capable of measuring the distance between two refer-ence points on the specimen without
38、 any damage to thespecimen or slippage, care being taken to ensure that themeasurement represents the true movement of the referencepoints. Examples of extensometers include mechanical, opti-cal, infrared, or electrical devices.7. Sampling7.1 Lot SampleDivide the product into lots, and take thelot s
39、ample as directed in Practice D4354.7.2 Laboratory SampleFor the laboratory sample, take afull roll width swatch long enough in the machine directionfrom each roll in the lot sample to ensure that the requirementsin 8.1 can be met. The sample may be taken from the endportion of a roll provided there
40、 is no evidence it is distorted ordifferent from other portions of the roll.8. Test Specimen8.1 The specimens shall consist of three junctions or300 mm (12 in.) in length, in order to establish a minimumspecimen length in the direction of the test (either the machine,cross-machine or some other dire
41、ction, if appropriate). Allspecimens should be free of surface defects, etc., not typical ofthe laboratory sample. Take no specimens nearer the selvageedge along the geogrid than110 the width of the sample.NOTE 1If comparing one geogrid to another, the length of eachspecimen shall be the same (as si
42、milar as possible) and agreed upon by allparties.8.2 Preparation:8.2.1 Test Method APrepare each finished specimen to bea minimum of 200 mm (8 in.) wide and contain at least five ribsin the cross-test direction by at least three junctions (twoapertures) or 300 mm (12 in.) long in the direction of te
43、sting,with the length dimension being designated and accurately cutparallel to the direction for which the tensile strength is beingmeasured.8.2.2 Test Method BPrepare each finished specimen to bea minimum of 200 mm (8 in.) wide and contain five ribs in thecross-test direction by at least three junc
44、tions (two apertures) or300 mm (12 in.) long in the direction of testing, with the lengthdimension being designated and accurately cut parallel to thedirection for which the tensile strength is being measured. Thisshall be repeated for each layer of geogrid included in the test.8.2.3 Test Method CPr
45、epare each finished specimen to bea minimum of 200 mm (8 in.) wide (excluding fringe whenapplicable, see 8.2.5) by at least 200 mm (8 in.) long (see 8.2.5)with the length dimension being designated and accuratelyparallel to the direction for which the tensile modulus is beingmeasured. Centrally, dra
46、w two lines running the full width ofthe specimen, accurately perpendicular to the length dimensionand separated by 100 mm (4 in.) to designate the gauge area.8.2.4 For some woven geotextiles, it may be necessary tocut each specimen 210 mm (8.5 in.) wide and then remove anequal number of yarns from
47、each side to obtain the 200 mm (8in.) finished dimension. This helps maintain specimen integrityduring the test.8.2.5 For geotextiles where specimen integrity is not af-fected, the specimens may be initially cut to the finished width.8.2.6 When the wet tensile modulus of the geotextile isrequired in
48、 addition to the dry tensile modulus, cut each testspecimen at least twice as long as is required for a standard test(see Note 2). Number each specimen and then cut it crosswiseinto two parts: one for determining the conditioned tensilemodulus and the other for determining the wet tensile modulus.Ea
49、ch portion shall bear the specimen number. In this manner,each paired break is performed on test specimens containingthe same yarns.NOTE 2For geotextiles which shrink excessively when wet, cut thetest specimens for obtaining wet tensile strength longer in dimension thanthat for dry tensile strength.8.3 Number of Test Specimens:8.3.1 Unless otherwise agreed upon as when provided in anapplicable material specification, take a number of test speci-mens per swatch in the laboratory sample such that the usermay expect at the 95 % probability level that
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