1、Designation: D 6638 07Standard Test Method forDetermining Connection Strength Between GeosyntheticReinforcement and Segmental Concrete Units (ModularConcrete Blocks)1This standard is issued under the fixed designation D 6638; the number immediately following the designation indicates the year oforig
2、inal adoption or, in the case 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 connectionproperties
3、 between a layer of geosynthetic reinforcement andsegmental concrete block units used in construction of rein-forced soil retaining walls. The test is carried out underconditions determined by the user that reproduce the connec-tion system at full-scale. The results of a series of tests are usedto d
4、efine a relationship between connection strength for asegmental unit-geosynthetic connection system and normalload.1.2 This is a performance test used to determine propertiesfor design of retaining wall systems utilizing segmental con-crete units and soil reinforcing geosynthetics, either geotextile
5、sor geogrids. The test is performed on a full-scale constructionof the connection and may be run in a laboratory or the field.1.3 The values stated in SI units are regarded as thestandard. The values stated in inch-pound units are providedfor information only.1.4 This standard may involve hazardous
6、materials, opera-tions, and equipment. This standard does not purport toaddress all of the safety concerns, if any, associated with itsuse. It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitat
7、ions prior to use.2. Referenced Documents2.1 ASTM Standards:2D 448 Classification for Sizes of Aggregate for Road andBridge ConstructionD 4354 Practice for Sampling of Geosynthetics for TestingD 4439 Terminology for GeosyntheticsD 4495 Test Method for Impact Resistance of Poly(VinylChloride) (PVC) R
8、igid Profiles by Means of a FallingWeightD 6637 Test Method for Determining Tensile Properties ofGeogrids by the Single or Multi-Rib Tensile Method3. Terminology3.1 Definitions:3.1.1 displacement criteria, na user prescribed maximummovement, mm (in.), of the geosynthetic reinforcement outfrom the ba
9、ck of segmental concrete units.3.1.2 geosynthetic, na planar product manufactured frompolymeric material used with soil, rock, earth, or other geo-technical engineering related material as an integral part of aman-made project, structure or system. (D 4439)3.1.3 granular infill, ncoarse grained soil
10、 aggregate usedto fill the voids in and between segmental concrete units.3.1.4 peak connection strength, nthe maximum tensilecapacity of the connection between geosynthetic reinforcementand segmental concrete units.3.1.5 segmental concrete unit (modular concrete block),na concrete unit manufactured
11、specifically for mortarless,dry-stack retaining wall construction.3.1.6 segmental concrete unit width, nthe segmental con-crete unit dimension parallel to the wall face and coincidentwith the geosynthetic reinforcement test specimen width.3.1.7 service state connection strength, n the connectiontens
12、ile capacity at a service state displacement criterion be-tween geosynthetic reinforcement and segmental concreteunits.3.2 For definition of other terms relating to geosynthetics,refer to Terminology D 4439.4. Summary of Test Method4.1 One end of a wide geosynthetic reinforcement testspecimen is att
13、ached to dry stacked segmental concrete blockunits assembled as specified by the user. The other end of thetest specimen is attached to a clamp, which is part of a constantrate of extension tensile loading machine. The top course ofsegmental concrete block units is then loaded vertically to aconstan
14、t normal load and the geosynthetic is then tensioned1This test method is under the jurisdiction of ASTM Committee D35 onGeosynthetics and is the direct responsibility of Subcommittee D35.01 on Mechani-cal PropertiesCurrent edition approved June 1, 2007. Published July 2007. Originally approvedin 200
15、1. Last previous edition approved in 2006 as D 6638 06.2For 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.1Copyr
16、ight ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.under constant rate of displacement until a sustained loss ofconnection capacity and/or excessive movement (greater than150 mm) of the reinforcement out from the connection.4.1.1 Peak connect
17、ion capacity, and tensile capacity after auser prescribed displacement criteria has occurred, is used todefine connection strength based on peak and service statecriteria respectively. Both these values may be obtained fromeach test that measures geosynthetic displacement. Tensileloads and strengths
18、 are reported per unit width of geosyntheticsample, kN/m (lb /ft). Generally a series of tests are performedto establish a mathematical relationship between connectionstrength and normal load on the connection.5. Significance and Use5.1 The connection strength between geosynthetic rein-forcement and
19、 segmental concrete block units is used in designof reinforced soil retaining walls.5.2 This test is used to determine the connection strength forthe design of the connection system formed by segmentalconcrete block units and geosynthetic reinforcement layers inreinforced soil retaining walls. Perfo
20、rming a series of theseconnection tests at varying normal loads permits developmentof a relationship between connection strength and normal load.This relationship may be linear, bi-linear, or some othercomplex mathematical expression.5.3 This connection strength test is meant to be a perfor-mance te
21、st (laboratory or field), therefore, it should be con-ducted using full-scale system components. The conditions forthe test are selected by the user and are not for routine testing.5.4 As a performance test on full-scale system componentsit accounts for some of the variables in construction procedur
22、esand materials tolerance normally present for these types ofretaining wall systems.6. Apparatus6.1 Testing SystemAn example of a test apparatus andsetup is illustrated in Figs. 1 and 2. The principal componentsof the test apparatus are:6.1.1 loading frame,6.1.2 normal load piston/actuator,6.1.3 ver
23、tical loading platen, with stiff rubber mat or airbagto apply uniform vertical pressure to top of concrete blocks6.1.4 vertical load cell, to measure normal load6.1.5 geosynthetic loading clamp,6.1.6 horizontal piston/actuator, to load geosynthetic rein-forcement in tension6.1.7 horizontal load cell
24、 to measure geosynthetic tensileforce, and6.1.8 two (2) horizontal displacement measurement de-vices,to record displacement of the geosynthetic at the back ofthe segmental concrete blocks.6.2 Loading FrameThe loading frame shall have suffi-cient capacity to resist the forces developed by the horizon
25、taland vertical loading pistons/actuators.6.3 Tensile Loading Clamp and Loading AssembliesThegeosynthetic is gripped at its free end with a clamp extendingthe full width of the specimen. The clamp shall be capable ofapplying a uniform force across the full width of the testspecimen. A roller grip as
26、sembly may be used to apply thetensile load. For some geosynthetics it may be necessary toepoxy bond the geosynthetic to, or within, the clamp in orderto obtain a uniform stress distribution across the entire width ofthe test specimen.6.3.1 The tensile loading unit will generally be a constantrate o
27、f extension screw jack or hydraulic actuator that can bedisplacement rate controlled. The loading equipment shall havea capacity that is at least equal to 120 % of the wide striptensile strength of the geosynthetic (Test Methods D 4595 orD 6637) multiplied by the specimen width. The piston shall bec
28、apable of at least 150 mm (6 inches) of movement in order tofacilitate test set up and to ensure that there is adequate stroketo achieve failure of geosynthetic reinforcement specimens.NOTE 1Some systems (that is, modular concrete units with a depthgreater than 0.5 m) may need more than 150 mm of mo
29、vement to achievefailure of the connection.6.3.2 The orientation of the tensioning force shall be hori-zontal and perpendicular to the back of the segmental units andshall be applied at the elevation where the geosynthetic exitsthe back of the segmental units.6.4 Load CellsA calibrated load cell sha
30、ll be used tomeasure the tensile connection force and normal load duringthe test. The load cell used for measuring tension shall have acapacity that is greater than or equal to 120 % of the wide striptensile strength of the geosynthetic (Test Methods D 4595 orD 6637) multiplied by the specimen width
31、. The load cell usedfor measuring the normal surcharge load shall have a capacitythat is greater than or equal to 100 % of the maximumanticipated normal load. The load cells shall be accurate within6 0.5 % of its full-scale range.FIG. 1 Connection Strength Test SystemFIG. 2 Connection Test Apparatus
32、 (Plan View)D66380726.5 Displacement Measuring Devices Two linear variabledisplacement transducers (LVDTs) or similar electronic dis-placement measuring devices are recommended to continu-ously monitor the displacement of the geosynthetic out fromthe back of the concrete units. Alternatively, dial g
33、auges maybe read and recorded manually at regular intervals not greaterthan one minute. LVDTs, dial gauges or similar measuringdevices shall be accurate to 6 0.1 mm (60.005 in.).7. Sampling7.1 Segmental Concrete Units7.1.1 Segmental concrete units shall be full-size blocks andmeet the manufacturers
34、material and dimensional specifica-tions. Model or prototype units shall not be used unless it canbe demonstrated that they are equivalent to production units.7.1.2 The user shall specify and/or collect a sufficientsample of representative segmental units, from a standardproduction lot, to construct
35、 the anticipated number of testconfigurations for the connection system within the testingagencys load frame and testing system.7.1.3 The wall for connection testing shall be constructedusing randomly selected full-size (that is, full width) segmentalunits from the users sampling of a standard produ
36、ction lot, seesection 7.1.2. A maximum of two half width segmentalconcrete units may be used on only one course of the unitsbeing tested in a confined width test apparatus. Segmentalconcrete units may be re-used in testing if there is no cracking,abrasion or wearing of the concrete surfaces between
37、tests.7.1.4 Wall WidthThe wall for testing shall be constructedto a minimum of 750 mm (29.5 in.) in width and contain atleast one typical segmental concrete unit running bond joint.The segmental wall width for testing shall be at least as wideas the geosynthetic test specimen width (see 7.2.3). Test
38、ing ofsegmental concrete unit widths greater than 500 mm, may berepresented in this test by limiting the test wall to 1000 mm(39.4 in.) in width.NOTE 2Narrower wall widths may be used for testing, provided theconnection strength is proven to be unaffected by this reduction (seesection 7.2.3).7.1.5 C
39、onditioningThe segmental concrete unit test speci-men shall be brought to standard temperature and relativehumidity conditions for testing in a laboratory. The temperatureis to be 21 6 2C (70 6 4F) and the relative humidity of 656 10 %. For field-testing the specimen shall be brought toambient condi
40、tions for not less than one hour. The temperatureand humidity at the start and end of the test shall be recordedfor field-testing.7.2 Geosynthetic7.2.1 Sampling RequirementsThe latest version of ASTMsampling protocol for geotextiles (Practice D 4354) shall beused for the geosynthetic reinforcement m
41、aterial.7.2.2 ConditioningThe geosynthetic reinforcement testspecimen shall be brought to standard temperature and relativehumidity conditions for testing in a laboratory. The temperatureis to be 21 6 2C (70 6 4F) and the relative humidity of 606 10 %. For field-testing the specimen shall be brought
42、 toambient conditions for not less than one hour. The temperatureand humidity at the start and end of the test shall be recordedfor field-testing.7.2.3 Specimen WidthThe geosynthetic reinforcement testspecimen shall be a minimum of 750 mm (29.5 in.) in width.For tests that use two or more full segme
43、ntal retaining wallunits on the bottom course, the geosynthetic shall be an exactmultiple of the segmental retaining wall unit width totalingclosest to, but exceeding 750 mm (29.5 in.) in width. Forsegmental retaining wall unit widths greater than 500 mm (19.7in.) a geosynthetic specimen width of 10
44、00 mm (39.4 in.) maybe used.NOTE 3Narrower geosynthetic reinforcement specimen widths maybe used for a specific concrete unit, provided that sufficient testingdemonstrates that narrower samples provide an evaluation of connectionperformance that is equivalent to the minimum 750 mm (29.5 in.) widthsa
45、mple. This procedure may be appropriate for wall connections that areprimarily mechanical (non-frictional) in nature.7.2.4 Specimen LengthThe geosynthetic specimen shallhave sufficient length to cover the interface surface as specifiedby the user. The specimen must be trimmed to providesufficient an
46、chorage at the geosynthetic loading clamp and afree length between the back of the concrete blocks and loadingclamp ranging from a minimum of 200 mm (7.9 in.) to amaximum of 600 mm (23.6 in.), The geosynthetic reinforce-ment specimen shall be placed between the stacked segmentalconcrete units to cov
47、er the same area that will be used in fieldconstruction of the connection or as determined by the user.7.2.5 A new geosynthetic reinforcement test specimen shallbe used for each test.7.2.6 Number of TestsA sufficient number of tests shall beconducted to adequately define a relationship between conne
48、c-tion strength and normal load applied to the connection. Testsshall be conducted at a minimum of five (5) unique normalloads within the range of loads typical of wall design, asdirected by the user.Additionally, at least two more tests at onenormal load will be necessary to verify repeatability (s
49、eesection 7.2.7).7.2.7 Repeatability of Test ResultsThe testing agencyshall provide evidence of test results repeatability by conduct-ing at least three tests at one normal load level for a specificsegmental concrete units and geosynthetic reinforcement sys-tem. The general range for repeatability of peak connectionstrength of these three nominally identical tests is 6 10 % fromthe mean of the three tests (see reference in X1.1). If the testresults are outside of this range it shall be duly noted on thereport.8. Test Procedure8.1 Install and brace lower co
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