1、Designation: D 6916 06cStandard Test Method forDetermining the Shear Strength Between SegmentalConcrete Units (Modular Concrete Blocks)1This standard is issued under the fixed designation D 6916; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、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 shear strengthbetween two layers of segmental conc
3、rete block units used inconstruction of reinforced soil retaining walls. The test iscarried out under conditions determined by the user thatreproduce the facing system at full-scale. The results of a seriesof tests are used to define a relationship between shear strengthdeveloped between segmental c
4、oncrete units and normal load.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 geogrids. The test is performed on a full-scale constructionof the facing system
5、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 materials, opera-tions, and equipment. This standard does not purport toaddress al
6、l 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 limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 448 Classification
7、for Sizes of Aggregate for Road andBridge ConstructionD 4354 Practice for Sampling of Geosynthetics for TestingD 4439 Terminology for GeosyntheticsD 4595 Test Method for Tensile Properties of Geotextilesby the Wide-Width Strip MethodD 6637 Test Method for Determining Tensile Properties ofGeogrids by
8、 the Single or Multi-Rib Tensile Method3. Terminology3.1 Definitions:3.1.1 displacement criteria, na user prescribed maximummovement, mm (in.), of the top segmental concrete unit outfrom the back of lower segmental concrete units.3.1.2 geosynthetic, na planar product manufactured frompolymeric mater
9、ial used with soil, rock, earth, or other geo-technical engineering related material as an integral part of aman-made project, structure or system. D 44393.1.3 granular infill, ncoarse grained soil aggregate usedto fill the voids in and between segmental concrete units.3.1.4 peak shear strength, nth
10、e maximum shear capacitybetween segmental concrete units.3.1.5 segmental concrete depth, nthe segmental concreteunit dimension perpendicular to the wall face.3.1.6 segmental concrete unit (modular concrete block),na concrete unit manufactured specifically for mortarless,dry-stack retaining wall cons
11、truction.3.1.7 segmental concrete unit width, nthe segmental con-crete unit dimension parallel to the wall face.3.2 For definition of other terms relating to geosynthetics,refer to Terminology D 4439.4. Summary of Test Method4.1 In this test method, segmental concrete units are as-sembled in two row
12、s (layers). The bottom row is laterallyrestrained. The top row is loaded vertically to a constantsurcharge load and the interface is sheared at a constant rate ofdisplacement until a drop of load after the peak load occurs.The test may be run with the geosynthetic reinforcementsandwiched between the
13、 two rows of segmental concrete unitsto determine the shear strength between segmental concreteunits at the connection between the units and the geosyntheticreinforcement.5. Significance and Use5.1 The shear strength between segmental concrete units(with and without geosynthetic reinforcement) and i
14、s used indesign of reinforced soil retaining walls.5.2 This test is used to determine the shear strength for thedesign of the facing stability of segmental retaining walls.Performing a series of these shear tests at varying normal loads1This test method is under the jurisdiction of ASTM Committee D3
15、5 onGeosynthetics and is the direct responsibility of Subcommittee D35.01 on Mechani-cal Properties.Current edition approved Nov. 15, 2006. Published December 2006. Originallyapproved in 2003. Last previous edition approved in 2006 as D 691606b.2For referenced ASTM standards, visit the ASTM Web Site
16、, 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 web site.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States
17、.permits development of a relationship between shear strengthand normal load. This relationship may be linear, bi-linear, orsome other complex mathematical expression.5.3 This shear strength test is meant to be a performance test(laboratory or field), therefore, it should be conducted usingfull-scal
18、e system components. The conditions for the test areselected 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 proceduresand materials tolerance normally present for these types ofretaining wall
19、systems.6. Apparatus6.1 Testing SystemAn example of a test apparatus andsetup is illustrated in Fig. 1. The principal components of thetest apparatus are:6.1.1 Loading Frame.6.1.2 Normal Load Piston/Actuator.6.1.3 Vertical Loading Platen, with stiff rubber mat orairbag to apply uniform vertical pres
20、sure to top of concreteblocks.6.1.4 Vertical Load Cell, to measure normal load.6.1.5 Horizontal Piston/Actuator, to apply horizontal loadon the top segmental concrete unit.6.1.6 Horizontal Load Cell, to measure applied force on thetop segmental concrete unit.6.1.7 Two (2) Horizontal Displacement Mea
21、surement De-vices, to record displacement of the top segmental concreteunit.6.2 Loading FrameThe loading frame shall have suffi-cient capacity to resist the forces developed by the horizontaland vertical loading pistons/actuators.6.3 Shear Loading PlateThe shear loading plate must besufficiently rig
22、id to apply a uniform force across the full widthof the top course. For some segmental units it may benecessary to apply the load through a deformable material (thatis, stiff rubber) which will conform to an irregular blocksurface, thereby allowing for a uniform load distribution.6.4 Restraining Box
23、/PlateA rigid restraining box/plate isrequired to prevent horizontal movement of the lowermostsegmental concrete units during shear testing. The restrainingbox/plate area shall be of sufficient width and depth toaccommodate the full scale “as manufactured” segmentalconcrete units being tested.6.5 Sh
24、ear Loading AssemblyThe tensile loading unit willgenerally be a constant rate of extension screw jack orhydraulic actuator that can be displacement rate controlled.The loading equipment shall have a capacity that is at leastequal to 120 % of the anticipated shear strength of thesegmental concrete un
25、its. The piston shall be capable of at least150 mm (6 in.) of movement in order to facilitate test set upand to ensure that there is adequate stroke to achieve peak load.The orientation of the tensioning force shall be horizontal andperpendicular to the back of the segmental units. The horizon-tal l
26、oading arrangement must not permit rotation of the topconcrete unit during shear.6.6 Load CellsA calibrated load cell shall be used tomeasure the shear force and normal load during the test. TheFIG. 1 Shear Test Apparatus (Cross Section View)D 6916 06c2load cell used for measuring shear shall have a
27、 capacity that isgreater than or equal to 120 % of the anticipated shear forcebetween units. The load cell used for measuring the normalsurcharge load shall have a capacity that is greater than orequal to 100 % of the maximum anticipated normal load. Theload cells shall be accurate within 6 0.5 % of
28、 its full-scalerange.6.7 Displacement Measuring DevicesTwo (2) LinearVariable Displacement Transducers (LVDTs) or similar elec-tronic displacement measuring devices are recommended tocontinuously monitor the displacement of the top segmentalconcrete unit out from the back of the lower segmentalconcr
29、ete units. Alternatively, dial gauges may be read andrecorded manually at regular intervals not greater than oneminute. LVDTs, dial gauges or similar measuring devices shallbe accurate to 6 0.1 mm (0.005 in.).7. Sampling7.1 Segmental Concrete Units:7.1.1 Segmental concrete units shall be full-size b
30、locks andmeet the manufacturers 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 stan
31、dardproduction lot, to construct the anticipated number of testconfigurations for the shear system within the testing agencysload frame and testing system.7.1.3 The shear interface must be constructed with full-sizeor modified (see 7.1.4) segmental concrete units randomlyselected from the users samp
32、ling of a standard production lot,see 7.1.2.7.1.4 Test Width The width of the shear interface fortesting shall be constructed to a minimum of 750 mm (29.5 in.)in width. The test section shall consist of at least two bottomcourse segmental concrete units with at least one top coursesegmental unit pla
33、ced on top of the lower segmental concreteunits. The shear interface shall include at least one typicalsegmental concrete unit running bond joint. The top unit mustbe the full width of the unit. The bottom units may be adjustedto fit into the test apparatus. Testing of segmental concrete unitwidths
34、greater than 500 mm (19.7 in.), may be represented inthis test by limiting the test wall to 1000 mm (39.4 in.) inwidth.NOTE 1Any modification to the width of bottom units should main-tain the integrity of the test shear interface and insure that a representative(repeatable) test shear interface is m
35、aintained.7.1.5 Test HeightThe height of the segmental concreteunit may be reduced to facilitate handling and safety issues.Any modification to the segmental concrete unit height shallnot alter the geometry of the test shear interface and shall beclearly stated in the test report (see 10.2).7.1.6 Co
36、nditioningThe 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 condit
37、ions for not less than one hour. The temperatureand humidity at the start and end of the test shall be recordedfor field-testing.7.2 Geosynthetic (if required):7.2.1 If the segmental concrete units are to be used for ageosynthetic reinforced segmental retaining wall, then a layerof a specified geosy
38、nthetic material shall be placed between thesegmental concrete units.7.2.2 Sampling RequirementsThe latest version of ASTMsampling protocol for geotextiles (Practice D 4354) shall beused for the geosynthetic reinforcement material.7.2.3 ConditioningThe geosynthetic reinforcement testspecimen shall b
39、e 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 toambient conditions for not less than one hour. The temperatureand humidity
40、 at the start and end of the test shall be recordedfor field-testing.7.2.4 Specimen WidthWhen included, the geosyntheticreinforcement test specimen shall be the full width of the sheartest interface.7.2.5 Specimen LengthThe geosynthetic specimen shallhave sufficient length to cover the interface sur
41、face as specifiedby the user. The specimen must be trimmed to providesufficient anchorage at the actuator side of the test apparatus toprevent slippage of the front edge of the geosynthetic sample.7.2.6 A new geosynthetic reinforcement test specimen shallbe used for each test.7.2.7 Number of TestsA
42、sufficient number of tests shall beconducted to adequately define a relationship between shearstrength and normal load. Tests shall be conducted at aminimum of five (5) unique normal loads within the range ofloads typical of wall design, as directed by the user. Addition-ally, at least two more test
43、s at one normal load will benecessary to verify repeatability (see 7.2.8).7.2.8 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 rei
44、nforcement sys-tem. The general range for repeatability of peak shear strengthof these three nominally identical tests is 6 10 % from themean of the three tests. If the test results are outside of thisrange it shall be duly noted on the report.8. Procedure8.1 Install and brace lower course of concre
45、te segmentalunits. Place the units such that a running joint will be locatedalong the centerline of the test apparatus.8.1.1 The facing system shall be constructed using thegeosynthetic reinforcement (if required), granular infill, full-scale segmental concrete block units and connectors specifiedby
46、 the user. The number, type and arrangement of mechanicalconnectors shall also be specified by the user.8.1.2 A single course of segmental units shall be placed ona rigid base. A single segmental concrete unit will later (see8.5) be placed over the bottom course of units, with thegeosynthetic reinfo
47、rcement located and placed between theseD 6916 06c3courses as described by the user or in the same manneranticipated for field construction.8.2 Place and compact granular infill within (if required)and between the segmental concrete units to the densityspecified by the user.8.2.1 The granular infill
48、 for testing shall be specified by theuser.NOTE 2A typical granular infill would be crushed stone conformingto the size number 57 or 67 gradations in Classification D 448.8.3 Center geosynthetic reinforcement on the running bondjoint of the lower course of segmental concrete units. Place thegeosynth
49、etic reinforcement test specimen in the user-specifiedposition with respect to concrete keys, mechanical connectors,and the wall face. Record the geosynthetic reinforcement testspecimen width, length, and position on the concrete units.8.4 Place a single segmental concrete unit over the bottomlayer and center on the running joint.8.5 Place and compact granular infill within (if required) thesegmental concrete unit to the density specified by the user.Ensure that the top surface of the unit is level.8.6 Place the surcharge/roller plate arrangement (or a
