1、Designation: D 4632 08Standard Test Method forGrab Breaking Load and Elongation of Geotextiles1This standard is issued under the fixed designation D 4632; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、 number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method is an index test which provides apro
3、cedure for determining the breaking load (grab strength)and elongation (grab elongation) of geotextiles using the grabmethod. This test method is not suitable for knitted fabrics andalternate test methods should be used. While useful for qualitycontrol and acceptance testing for a specific fabric st
4、ructure,the results can only be used comparatively between fabricswith very similar structures, because each different fabricstructure performs in a unique and characteristic manner in thistest. The grab test methods does not provide all the informationneeded for all design applications and other te
5、st methodsshould be used.1.2 Procedures for measuring the breaking load and elon-gation by the grab method in both the dry and wet state areincluded; however, testing is normally done in the dry condi-tion unless specified otherwise in an agreement or specifica-tion.1.3 The values stated in SI units
6、 are to be regarded asstandard. The values stated in inch-pound units are providedfor information only.1.4 This 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 h
7、ealth practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D76 Specification for Tensile Testing Machines for TextilesD 123 Terminology Relating to TextilesD 1776 Practice for Conditioning and Testing TextilesD 2905 Practice for
8、 Statements on Number of Specimensfor TextilesD 4354 Practice for Sampling of Geosynthetics for TestingD 4439 Terminology for Geosynthetics3. Terminology3.1 Definitions:3.1.1 atmosphere for testing geotextiles, n air maintainedat a relative humidity of 65 6 5 % relative humidity andtemperature of 21
9、 6 2C (70 6 4F).3.1.2 breaking load, nthe maximum force applied to aspecimen in a tensile test carried to rupture.3.1.3 cross-machine direction, nthe direction in the planeof the fabric perpendicular to the direction of manufacture.3.1.4 elongation at break, nthe elongation correspondingto the break
10、ing load, that is, the maximum load.3.1.5 geotextile, nany permeable textile material usedwith foundation, soil, rock, earth, or any other geotechnicalmaterial, as an integral part of a man-made product, structure,or system.3.1.6 grab test, nin fabric testing, a tension test in whichonly a part of t
11、he width of the specimen is gripped in theclamps.3.1.6.1 DiscussionFor example, if the specimen width is101.6 mm (4 in.) and the width of the jaw faces 25.4 mm (1in.), the specimen is gripped centrally in the clamps.3.1.7 machine direction, nthe direction in the plane of thefabric parallel to the di
12、rection of manufacture.3.1.8 For definitions of other terms used in this test method,refer to Terminology D 123 or Terminology D 4439.4. Summary of Test Method4.1 A continually increasing load is applied longitudinallyto the specimen and the test is carried to rupture. Values for thebreaking load an
13、d elongation of the test specimen are obtainedfrom machine scales or dials, autographic recording charts, orinterfaced computers.5. Significance and Use5.1 The grab method is applicable whenever it is desired todetermine the “effective strength” of the fabric in use, that is,the strength of the mate
14、rial in a specific width, together with1This test method is under the jurisdiction of ASTM Committee D35 onGeosynthetics and is the direct responsibility of Subcommittee D35.01 on Mechani-cal Properties.Current edition approved July 1, 2008. Published May 1991. Originally approvedin 1991. Last previ
15、ous edition approved in 2003 as D 463291(2003).2Annual Book of ASTM Standards, Vol 07.01.For 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 Summa
16、ry page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.the additional strength contributed by adjacent material. Thereis no simple relationship between grab tests and strip tests sincethe amount of fabric assistan
17、ce depends on the construction ofthe fabric. It is useful as a quality control or acceptance test.5.2 The procedure in Test Method D 4632 for the determi-nation of grab strength of geotextiles may be used for accep-tance testing of commercial shipments, but caution is advisedsince information about
18、between-laboratory precision is in-complete. Comparative tests as directed in 5.2.1 are advisable.5.2.1 In case of a dispute arising from differences inreported test results when using the procedures in Test MethodD 4632 for acceptance testing of commercial shipments, thepurchaser and the manufactur
19、er should conduct comparativetests to determine if there is a statistical bias between theirlaboratories. Competent statistical assistance is recommendedfor the investigation of bias. As a minimum, the two partiesshould take a group of test specimens that are as homogeneousas possible and which are
20、from a lot of material of the type inquestion. The test specimens should then be randomly assignedin equal numbers to each laboratory for testing. The averageresults from the two laboratories should be compared using theappropriate Students t-test and an acceptable probability levelchosen by the two
21、 parties before testing is begun. If a bias isfound, either its cause must be found and corrected or thepurchaser and the manufacturer must agree to interpret futuretest results in the light of the known bias.5.3 Most geotextile fabrics can be tested by this test method.Some modification of clamping
22、 techniques may be necessaryfor a given fabric, depending upon its structure. Specialadaptation may be necessary with strong fabrics, or fabricsmade from glass fibers, to prevent them from slipping in theclamps or being damaged as a result of being gripped in theclamps, such as cushioning the clamp
23、or boarding the specimenwithin the clamp.5.4 This test method is applicable for testing fabrics eitherdry or wet. It may be used with constant-rate-of-traverse (CRT)or constant-rate-of-extension (CRE) type tension machines.However, there may be no overall correlation between theresults obtained with
24、 the CRT machine and the CRE machine.Consequently, these two tension testers cannot be used inter-changeably. In case of controversy, the CRE machine shallprevail.6. Apparatus6.1 Tensile Testing Machine, of the constant-rate-of-extension (CRE) or constant-rate-of-traverse (CRT) type withautographic
25、recorder conforming to the requirements of Speci-fication D76.6.2 Clamps, having all gripping surfaces parallel, flat, andcapable of preventing slipping of the specimen during a test.Each clamp shall have one jaw face measuring 25.4 by 50.8mm (1 by 2 in.), with the longer dimension parallel to thedi
26、rection of application of the load. The other jaw face of eachclamp shall be at least as large as its mate. Each jaw face shallbe in line, both with respect to its mate in the same clamp andto the corresponding jaw of the other clamp.7. Sampling and Selection7.1 Division into Lots and Lot Samples Di
27、vide the mate-rial into lots and take a lot sample as directed in PracticeD 4354. Rolls of fabric are the primary sampling unit.7.2 Laboratory SampleTake for the laboratory sample aswatch extending the width of the fabric and approximately 1m (39.37 in.) along the selvage from each roll in the lot s
28、ample.The swatch may be taken from the end portion of a rollprovided there is no evidence that it is distorted or differentfrom other portions of the roll. In cases of dispute, take aswatch that will exclude fabric from the outer wrap of the rollor the inner wrap around the core.7.3 Test SpecimensCu
29、t the number of specimens fromeach swatch in the laboratory sample determined as directed inSection 8. Take no specimens nearer the selvage of fabric edgethan120 of the fabric width or 150 mm (6 in.), whichever is thesmaller. Cut rectangular specimens 101.6 by 203.2 mm (4 by 8in.). Cut the specimens
30、 to be used for grab tests in the machinedirection with the longer dimension parallel to the machinedirection and the specimens to be used for grab tests in thecross-machine direction with the longer dimension parallel tothe cross-machine direction. Locate each group of specimensalong a diagonal lin
31、e on the swatch so that each specimen willcontain different warp ends and filling picks. Draw a line 37mm (1.5 in.) from the edge of the specimen running its fulllength. For woven and reinforced nonwoven fabrics, this linemust be accurately parallel to the lengthwise yarns in thespecimen.8. Number o
32、f Specimens8.1 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 the test result isno more than 5 % above the true average for each
33、 swatch in thelaboratory sample for each the machine and cross-machinedirection, respectively.8.1.1 Reliable Estimate of vWhen there is a reliableestimate of v based upon extensive past records for similarmaterials tested in the users laboratory as directed in themethod, calculate the required numbe
34、r of specimens using Eq1, as follows:n 5 tv/A!2(1)where:n = number of test specimens (rounded upward to a wholenumber),v = reliable estimate of the coefficient of variation ofindividual observations on similar materials in theusers laboratory under conditions of single-operatorprecision, %,t = the v
35、alue of Students t for one-sided limits (see Table1), a 95 % probability level, and the degrees offreedom associated with the estimate of v, andA = 5.0 % of the average, the value of the allowablevariation.8.1.2 No Reliable Estimate of vWhen there is no reliableestimate of v for the users laboratory
36、, Eq 1 should not be usedD4632082directly. Instead, specify the fixed number of 10 specimens forthe machine direction tests and 10 specimens for the cross-machine direction tests. The number of specimens is calculatedusing v = 9.5 % of the average for both machine direction andcross-machine directio
37、n. These values for v are somewhatlarger than usually found in practice. When a reliable estimateof v for the users laboratory becomes available, Eq 1 willusually require fewer than the fixed number of specimens.9. Conditioning9.1 Bring the specimens to moisture equilibrium in theatmosphere for test
38、ing geotextiles. Equilibrium is considered tohave been reached when the increase in mass of the specimenin successive weighings made at intervals of not less than 2 hdoes not exceed 0.1 % of the mass of the specimen. In generalpractice, the industry approaches equilibrium from the “asreceived” side.
39、NOTE 1It is recognized that in practice geotextile materials arefrequently not weighed to determine when moisture equilibrium has beenreached. While such a procedure cannot be accepted in cases of dispute,it may be sufficient in routine testing to expose the material to the standardatmosphere for te
40、sting for a reasonable period of time before thespecimens are tested. A time of at least 24 h has been found acceptable inmost cases. However, certain fibers may exhibit slow moisture equiliza-tion rates from the “as received” wet side. When this is known, apreconditioning cycle, as described in Pra
41、ctice D 1776, may be agreedupon between contractural parties.9.2 Specimens to be tested in the wet condition shall beimmersed in water maintained at a temperature of 21 6 2C(706 4F). The time of immersion must be sufficient to wet-outthe specimens thoroughly, as indicated by no significantchange in
42、strength or elongation following a longer period ofimmersion, and at least 2 min. To obtain thorough wetting, itmay be necessary or advisable to add not more than 0.05 % ofa nonionic neutral wetting agent to the water.10. Procedure10.1 Test the conditioned specimens in the standard atmo-sphere for t
43、esting in accordance with Section 9.10.2 Set the distance between the clamps at the start of thetest at 75 6 1mm(36 0.05 in.). Select the load range of thetesting machine such that the maximum load occurs between10 and 90 % of full-scale load. Set the machine to operate at aspeed of 300 6 10 mm/min
44、(12 6 0.5 in./min).10.3 Secure the specimen in the clamps of the testingmachine, taking care that the long dimension is as nearly aspossible parallel to the direction of application of the load. Besure that the tension in the specimen is uniform across theclamped width. Insert the specimen in the cl
45、amps so thatapproximately the same length of fabric extends beyond thejaw at each end. Locate the jaws centrally in the widthwisedirection by having the line which was drawn 37 mm (1.5 in.)from the edge of the specimen run adjacent to the side of theupper and lower front jaws which are nearest this
46、edge. Thisensures that the same lengthwise yarns are gripped in bothclamps.10.4 If a specimen slips in the jaws, breaks at the edge of orin the jaws, or if for any reason attributed to a faulty operationthe result falls markedly below the average for the set ofspecimens, discard the result and take
47、another specimen.Continue this procedure until the required number of accept-able breaks have been obtained.NOTE 2The decision to discard a break shall be based on observationof the specimen during the test and upon the inherent variability of thefabric. In the absence of other criteria for rejectin
48、g a so-called jaw break,any break occurring within 5 mm (14 in.) of the jaws which results in avalue below 80 % of the average of all the other breaks shall be discarded.No other break shall be discarded unless it is known to be faulty.NOTE 3It is difficult to determine the precise reason for breaka
49、ge oftest specimens near the edge of the jaws. If breaks are caused by damageto the specimen by the jaws, then the results should be discarded. If,however, they are merely due to randomly distributed weak places inspecimens, the results should be considered perfectly legitimate. In somecases, breaks may be caused by a concentration of stress in the areaadjacent to the jaws. If this occurs, the specimen is prevented fromcontracting in width as the load is applied. In such cases, a break near theedge of the jaws is inevitable and shall be accepted as a chara
