1、Designation: D6638 11Standard Test Method forDetermining Connection Strength Between GeosyntheticReinforcement and Segmental Concrete Units (ModularConcrete Blocks)1This standard is issued under the fixed designation D6638; the number immediately following the designation indicates the year oforigin
2、al adoption or, in 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 This test method is used to determine the connectionproperties be
3、tween 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 defi
4、ne 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 geotextilesor
5、 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 mat
6、erials, 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 limitation
7、s prior to use.2. Referenced Documents2.1 ASTM Standards:2D448 Classification for Sizes of Aggregate for Road andBridge ConstructionD4354 Practice for Sampling of Geosynthetics for TestingD4439 Terminology for GeosyntheticsD4495 Test Method for Impact Resistance of Poly(VinylChloride) (PVC) Rigid Pr
8、ofiles by Means of a FallingWeightD6637 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 back of se
9、gmental 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. (D4439)3.1.3 granular infill, ncoarse grained soil aggregat
10、e 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 specifica
11、lly 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 connectiontensile capac
12、ity 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 D4439.4. Summary of Test Method4.1 One end of a wide geosynthetic reinforcement testspecimen is attached to d
13、ry 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 aconstant normal l
14、oad 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, 2011. Published July 2011. Originally approvedin 2001. Last pr
15、evious edition approved in 2007 as D6638 07. DOI: 10.1520/D6638-11.2For 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 we
16、bsite.1Copyright 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
17、Peak connection 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 a
18、nd strengths 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-f
19、orcement and 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
20、walls. Performing 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 per
21、for-mance test (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 construct
22、ion proceduresand 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/actuat
23、or,6.1.3 vertical 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 horizont
24、al load cell to measure geosynthetic tensileforce, and6.1.8 two (2) horizontal displacement measurement devic-es,to record displacement of the geosynthetic at the back of thesegmental concrete blocks.6.2 Loading FrameThe loading frame shall have suffi-cient capacity to resist the forces developed by
25、 the horizontaland 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 ro
26、ller grip assembly 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 co
27、nstantrate of 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 D4495 orD6637) multiplied by the specimen width. The piston
28、 shall becapable 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 15
29、0 mm of movement 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 loa
30、d cell shall 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 D4495 orD6637) multiplied by the specim
31、en width. 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 A
32、pparatus (Plan View)D6638 1126.5 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. Alternativel
33、y, dial gauges 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 manuf
34、acturers 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
35、construct 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 stand
36、ard production 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
37、 between 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
38、.3). Testing 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
39、).7.1.5 ConditioningThe 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 toambi
40、ent 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 Geosynthetic7.2.1 Sampling RequirementsThe latest version of ASTMsampling protocol for geotextiles (Practice D4354) shall beused for the geosynthetic reinfor
41、cement material.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
42、 brought 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 fu
43、ll segmental 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 wid
44、th of 1000 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.)
45、 widthsample. 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 providesuffi
46、cient anchorage 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 unit
47、s to cover 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 betwe
48、en connec-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 repeatab
49、ility (seesection 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 brac
