1、Designation: D7737 11D7737/D7737M 15Standard Test Method forIndividual Geogrid Junction Strength1This standard is issued under the fixed designation D7737;D7737/D7737M; the number immediately following the designation indicatesthe year of original adoption or, in the case of revision, the year of la
2、st revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method is an index test which provides a procedure for determining the strength of an individual geogrid junct
3、ion,also called a node. The test is configured such that a single rib is pulled from its junction with a cross-rib to rib(s) transverse tothe test direction to obtain the maximum force, or strength of the junction. The procedure allows for the use of two different clampswith the appropriate clamp se
4、lected to minimize the influence of the clamping mechanism on the specific type of geogrid to betested.1.2 The values stated in either SI units or inch-pound units are to be regarded as the separately as standard. The values statedin each system may not be exact equivalents; therefore, each system s
5、hall be used independently of the other. Combining valuesfrom the two systems may result in non-conformance with the standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish a
6、ppropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D4354 Practice for Sampling of Geosynthetics and Rolled Erosion Control Products(RECPs) for TestingD4439 Terminology for GeosyntheticsD5262 Test Met
7、hod for Evaluating the Unconfined Tension Creep and Creep Rupture Behavior of Geosynthetics3. Terminology3.1 Definitions of other terms applying to this test method appear in Terminology D4439.3.1 Definitions: Definitions of other terms applying to this test method appear in Terminology D4439.3.1.1
8、atmosphere for testing geosynthetics, nair maintained at a relative humidity of 50 to 70 % and a temperature of 21 62C (7070 6 4F).4F.3.1.2 breaking force, (F), nthe force at failure.3.2.3 geogrid, nthe force at failure.3.1.3 integral,geogrid, adjna geosynthetic formed by a regular network of integr
9、ally connected elements with aperturesgreater than 6.35 mm (14 inch)0.25 in. to allow interlocking with surrounding soil, rock, earth, and other surrounding materialsto primarily function as reinforcement. (D5262) D52623.1.4 index test, na test procedure which may contain known bias, but which may b
10、e used to establish an order for a set ofspecimens with respect to the property of interest.3.1.5 integral, adjin geosynthetics, forming a necessary part of the whole; a constituent.3.1.6 junction, nthe point where geogrid ribs are interconnected to provide structure and dimensional stability.3.1.7
11、rib, nfor geogrids, the continuous elements of a geogrid which are interconnected to a node or junction.either in themachine or cross-machine direction as manufactured.3.1.8 rupture, nfor geogrids, the breaking or tearing apart of ribs.1 This test method is under the jurisdiction ofASTM Committee D3
12、5 on Geosynthetics and is the direct responsibility of Subcommittee D35.01 on Mechanical Properties.Current edition approved Sept. 15, 2011July 1, 2015. Published November 2011September 2015. Originally approved in 2011. Last previous edition approved in 2011as D773711. DOI: 10.1520/D77311110.1520/D
13、7737_D7737M-152 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is in
14、tended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the cur
15、rent versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Summary of Test Method4.1 This standard proposes a test method for performing tension tests
16、on geogrid junctions. The procedure provides twoclamping techniques for the junction to be tested including: Method A in which the clamps firmly grip the ribs transverse to thetest direction on each side of the junction; and, Method B in which the ribs transverse to the test direction are constraine
17、d in a slot,constraining rotation of the junction, while the rib in the test direction passes through the slot without the junction clamp applyingconfinement to the junction. The junction clamping technique is selected for the specific type of geogrid in order to minimizerotation and corresponding p
18、eal of the junction during the test. The rib in the test direction going through the junction is thenclamped at a distance from the junction and the system tensioned until junction (or rib) failure occurs. This forces a tension or shearforce to occur within the junction in the direction of the appli
19、ed load. The junction has no normal pressure on it, i.e., that is, it ishorizontally unconfined.5. Significance and Use5.1 This index test method is to be used to determine the strength of an individual junction in a geogrid product. The test isperformed in isolation, while in service the junction i
20、s typically confined. Thus the results from this test method are not anticipatedto be related to design performance.5.2 The value of junction strength can be used for manufacturing quality control, development of new products, or a generalunderstanding of the in-isolation behavior of a particular ge
21、ogrids junction (for example.,example, in relation to handling duringshipment and placement of the geogrid).5.3 This test method is applicable to geogrid products with essentially symmetrical orthogonal or non-orthogonal ribs, yarns orstraps, that is, geogrids which are composed of ribs, yarns or st
22、raps that are entangled through weaving or knitting, welded, bondedor formed through drawing.6. Apparatus6.1 The test apparatus for this method consists of three parts; the tensile testing machine, the junction clamp and the rib clamp.6.2 Tensile Testing MachineTensile Testing Machine - The testing
23、machine should operate under a constant rate of extension.It should have the capabilities of measuring the tensile force, typically with a load cell having an adequate load capacity to coverthe full range of products to be tested. The test recorder must be able to adequately record the complete forc
24、e-elongation curveduring the test.6.3 Method A: Junction Clamp (Rotation is Unconstrained)Method A: Junction Clamp (Rotation is Unconstrained) - Theclamp assembly which holds the geogrid junction shall be of the same design or equivalent to that shown in Fig. 1. The clamp mustonly confine the horizo
25、ntal rib or adjacent rib(s) transverse to the junction on each side of the junction and not the junction itself.The ribs transverse to the test direction should be placed horizontally level such that torsion is not applied to the junction. Theclamp cannot hinder or influence the junction. The two mo
26、vable parts of the restraining clamp should be adjustable to allow thebearing surfaces to fit snugly without touching the junction of the geogrid product being tested.The clamp assembly should providethe appropriate clamping power to prevent slipping or crushing (damage) of the horizontal rib. The e
27、ntire clamp assembly is tobe placed in the upper portion of the testing machine.NOTE 1These clamps are particularly well suited for homogeneous extruded and woven geogrids with either essentially symmetrical orthogonal ornon-orthogonal ribs and longitudinal ribs concentric with transverse ribs.6.4 M
28、ethod B: Junction Clamp (Rotation is Constrained)Method B: Junction Clamp (Rotation is Constrained) - The clampsaccording to Fig. 32 must only confine the horizontal rib or adjacent rib(s) transverse to the test direction on each side of thejunction and not the junction itself. The clamps should con
29、tinuously support the transverse rib to the test direction such that torsionis not applied. The clamp cannot hinder or influence the junction. The insert clamp shall fit snugly into the opening of therestraining clamp. Fig. 32a is for geogrids with two straps welded together in one junction, Fig. 32
30、b is for geogrids with twohorizontal straps welded to one vertical strap. The screws in Fig. 32a and Fig. 32b are not needed if the insert clamp fits snuglyinto the opening of the restraining clamp. The entire clamp assembly is to be placed in the upper portion of the testing machine.The dimensions
31、of the insert clamp as stated in Fig. 32a and Fig. 32b should be as follows:a - average width of vertical strap mm (readability 0.1 mm) 0.1 mm) + 0.6 mmb - 5 -to 10 mmc - average thickness of junction mm (readability 0.1 mm) 0.1 mm) + 0.2 mmd - average thickness of vertical strap mm (readability 0.1
32、 mm) 0.1 mm) + 0.2 mmThe assembled configuration of these clamps is shown in Fig. 43.NOTE 2These clamps are particularly well suited for welded or strap geogrids with longitudinal ribs not concentric with transverse ribs. They arealso better suited than the unconstrained clamps for various woven and
33、 knit geogrids with transverse elements (that is, ribs or nodes) that tend to rotatewhen tension is applied.6.5 Rib ClampRib Clamp - The lower portion of the vertical rib passing through the clamp assembly is placed in a separateclamp at the base of the testing machine. This is typically the longitu
34、dinal rib of the geogrid test specimen. The clamp must beD7737/D7737M 152sufficiently wide to grip the entire rib and must have the appropriate clamping power to prevent slipping or crushing (damage).The suggested style of clamp is a wedge action type as used for a rib tensile strength test.NOTE 3It
35、 is also possible to reverse the positioning of the test assembly from that described in 6.3 and 6.4Sections 6.3 and 6.4. . In such a case, thejunction clamp would be in the base of the testing machine and the rib clamp in the crosshead adjacent to the load cell.7. Test Specimens7.1 The test specime
36、n shape is unique to the particular geogrid being tested. It generally involves specimens to be cut in theshape of a “T“ with at least one junction remaining on each side of the junction being tested. The direction of the test shall bedefined as a nominal angle (skew to the machine direction), accor
37、ding to Fig. 4, where machine direction (MD) is defined as 0and cross machine direction (CMD) as 90. See Fig. 25 for illustrations of some geogrid test specimens. For woven and knittedgeogrids where nodes may unravel when cut, adjacent ribs can be cut away from the node as shown in Fig. 5Figure 2d d
38、 tominimize the effect of cutting on the structure of the product. Fig. 5e shows the testing arrangement for symmetrical,non-orthogonal ribs. The specimens should be cut to allow for the maximum amount of transverse rib on each side of the junctionto be tested. The center rib shall be long enough (t
39、ypically a minimum of three bars or nodes), so as to allow for enough clampingaction within the rib clamp. The test specimens should be brought to standard test conditions of temperatures 21 6 2C (70706 4F)4F and tested under the same conditions. Relative humidity is not an issue for this test metho
40、d.7.2 Number of test specimens:Number of Test Specimens:7.2.1 Reliable Estimate of vReliable Estimate of vWhen When there is a reliable estimate of v based upon extensive pastrecords for similar materials tested in the users laboratory as directed in the method, calculate the required number of spec
41、imensusing Eq 1, as follows:FIG. 1 Typical Junction Strength Test Specimen Test Setup Rotation is not Constrained per 6.3Section 6.3D7737/D7737M 153FIG. 32 Alternative Clamp for Constraining Rotation of the Geogrid Junction per Section6.4 6.4D7737/D7737M 154FIG. 43 Entire Assembly for Constrained Ro
42、tation of the Geogrid Junction per Section6.4 6.4D7737/D7737M 155n 5tv/A!2 (1)where:where:n = number of test specimens (rounded upward to a whole number),v = reliable estimate of the coefficient of variation of individual observations on similar materials in the users laboratory underconditions of s
43、ingle-operator precision, %t = the value of Students t for one-sided limits, a 95 % probability level, and the degrees of freedom associated with theestimate of v, and;A = 5.0 % of the average, the value of allowable variation.7.2.2 No Reliable Estimate of vNo Reliable Estimate of vWhen When there i
44、s no reliable estimate of v for the userslaboratory, Eq 1 should not be used directly. Instead, there should be ten (10) replicate specimens tested in the direction of concern. This number of specimens is somewhat larger than usually found using a reliable estimate of v. When a reliable estimate of
45、vfor the users laboratory becomes available, Eq 1 will usually require fewer than the fixed number of specimens.8. Procedure8.1 Calibrate and balance the testing system.8.2 Install testing clamps; the junction clamp is typically the upper fixture and the rib clamp is then the lower fixture.8.3 Adjus
46、t the movable parts of the junction clamp to fit as closely to the vertical center rib as possible, without touching it orinfluencing it (that is, within 1 mm of the edge of the junction).8.4 Mount the specimen carefully in the upper clamps, tighten it with sufficient force to prevent slipping or da
47、mage of thespecimen and see that its alignment is proper to mate with the lower rib clamp.8.5 Mount the rib in the lower clamp so that bending or torsion is avoided and the rib is positioned so as to be uniaxiallytensioned with respect to the upper assembly.NOTE 4If Note 3 is followed, 8.4 and 8.5 w
48、ould be reversed.8.6 Set the constant rate of extension of the test machine to be 50 mm/min (2 in./min)2 in./min.8.7 Rebalance the test system and initiate the test by starting the testing machine and continue until rupture occurs. Record andreport the maximum force obtained to cause failure.8.8 Rep
49、eat the above procedure for ten (10) representative test specimens. Calculate the average junction strength per rib asdescribed in the following section.9. Calculations9.1 From the resulting test data, the average junction strength per rib “Javg“ is calculated;Javg5(151nJi/n (2)Jave5(151nJi/n (2)where:where:Javg = average junction strength per rib in kN (lb)Jave = average junction strength per rib in kN lbJi = test strength for each junction evaluated in kN (lb)FIG. 4 Specimen Orientation and Test DirectionD7737/D7
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