1、Designation: D7499/D7499M 09 (Reapproved 2014)Standard Test Method forMeasuring Geosynthetic-Soil Resilient Interface ShearStiffness1This standard is issued under the fixed designation D7499/D7499M; the number immediately following the designation indicates theyear of original adoption or, in the ca
2、se of revision, the year of last 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 details how cyclic loading is applied togeosynthetics embedded in soil to
3、 determine the apparentstiffness of the soilgeosynthetic interface.1.2 Resilient interface shear stiffness describes the shearstiffness between a geosynthetic and its surrounding soil underconditions of small cyclic loads.1.3 This test method is intended to provide properties fordesign. The test met
4、hod was developed for mechanistic em-pirical pavement design methods requiring input of the resilientinterface shear stiffness. The use of this parameter from thistest method for other applications involving cyclic loadingshould be evaluated on a case-by-case basis. It can also be usedto compare dif
5、ferent geosynthetics, soil types, etc., and therebybe used as a research and development test procedure.1.4 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be
6、used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.5 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-priat
7、e safety and health practices and determine the applica-bility of regulatory limitations prior to use. This standard mayinvolve hazardous materials, and equipment.2. Referenced Documents2.1 ASTM Standards:2D123 Terminology Relating to TextilesD653 Terminology Relating to Soil, Rock, and ContainedFlu
8、idsD3080/D3080M Test Method for Direct Shear Test of SoilsUnder Consolidated Drained ConditionsD4439 Terminology for GeosyntheticsD4354 Practice for Sampling of Geosynthetics and RolledErosion Control Products(RECPs) for Testing3. Terminology3.1 For definitions of other terms used in this test metho
9、drefer to Terminologies D123, D653, and D4439.3.2 Definitions of Terms Specific to This Standard:3.2.1 apertures, nthe open spaces in geogrids whichenable soil interlocking to occur.3.2.2 atmosphere for testing geosynthetics, nair main-tained at a relative humidity of 60 6 10 % and a temperatureof 2
10、1 6 2C 70 6 4F.3.2.3 cross-machine direction, nthe direction in the planeof the geosynthetic perpendicular to the direction of manufac-ture.3.2.4 failure, nan arbitrary point at which a materialceases to be functionally capable of its intended use.3.2.5 geosynthetic, na planar product manufactured f
11、rompolymeric material used with soil, rock, earth, or other geo-technical engineering related material as an integral part of aman-made project, structure, or system.3.2.6 geosynthetic-soil resilient interface shear stiffness,na parameter that describes the apparent stiffness of theinterface between
12、 the soil and the geosynthetic determined bycalculating the slope of the shear stress, shear displacementcurve as the embedded geosynthetic is subjected to a cyclicload.3.2.7 junction, nthe point where geogrid ribs are intercon-nected in order to provide structure and dimensional stability.3.2.8 mac
13、hine direction, nthe direction in the plane of thegeosynthetic parallel to the direction of manufacture.3.2.9 pullout, nthe movement of a geosynthetic over itsentire embedded length, with initial pullout occurring when theback of the specimen moves, and ultimate pullout occurringwhen the movement is
14、 uniform over the entire embeddedlength.1This 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 Sept. 1, 2014. Published September 2014. Originallyapproved in 2009. La
15、st previous edition approved in 2009 as D7499/D7499M09.DOI: 10.1520/D7499_D7499M-09R14.2For 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 Summar
16、y page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.10 pullout force, (kN), nforce required to pull ageosynthetic out of the soil during a pullout test.3.2.11 pullout resistance, (kN/m), nthe pullout force pe
17、rwidth of geosynthetic measured at a specified condition ofdisplacement.3.2.12 rib, nthe continuous elements of a geogrid whichare either in the machine or cross-machine direction asmanufactured.3.2.13 wire gage, na displacement gage consisting of anon extensible wire attached to the geosynthetic an
18、d monitoredby connection to a dial extensometer, or electronic displace-ment transducer.4. Summary of Test Method4.1 In this test method, a horizontal layer of geosynthetic isembedded between two layers of soil. Six prescribed levels ofhorizontal cyclic force are applied to the geosynthetic at fives
19、pecified levels of normal stress confinement. The maximumand minimum forces and corresponding displacements arerecorded for the last ten cycles of each combination of normalstress and cyclic force (loading sequence).4.2 The resilient interface shear stiffness (kPa/m or psi/in)of the test specimen ca
20、n be calculated for any loading sequenceby dividing the cyclic shear stress by the corresponding netrecoverable horizontal displacement of the embedded geosyn-thetic5. Significance and Use5.1 This test method is intended as a performance test toprovide the user with a set of design values for the te
21、stconditions examined.5.1.1 The test method is applicable to all geosynthetics andall soils when loaded in a cyclic manner.5.1.2 This test method produces test data, which can be usedin the design of geosynthetic-reinforced pavement structures orin applications where geosynthetics are subjected to c
22、yclicloads.5.1.3 The test results may also provide information relatedto the in-soil stress-strain response of a geosynthetic underconfined loading conditions.5.2 Information derived from this test may be a function ofsoil gradation, plasticity, as-placed dry unit weight, moisturecontent, length and
23、 surface characteristics of the geosyntheticand other test parameters. Therefore, results are expressed interms of the actual test conditions. The test measures the neteffect of a combination of interface shear mechanisms, whichmay vary depending on type of geosynthetic specimen, em-bedment length,
24、relative opening size, soil type, displacementrate, normal stress, and other factors.5.3 Information between laboratories on precision is incom-plete. In cases of dispute, comparative tests to determine ifthere is a statistical bias between laboratories may be advis-able.6. Apparatus6.1 Test BoxAn o
25、pen rigid box consisting of two smoothparallel sides, a back wall, a horizontal split removable door, abottom plate, and a load transfer sleeve. The door is at the frontas defined by the direction of applied cyclic force. A typicalbox is shown in Fig. 1.6.1.1 The box should be square or rectangular
26、with mini-mum dimensions 457 mm 18 in. long by 457 mm 18 in.wide by 305 mm 12 in. deep, if sidewall friction isminimized, otherwise the minimum width should be 760 mm30 in. The dimensions should be increased, if necessary, sothat minimum width is the greater of 20 times the D85 of thesoil or 6 times
27、 the maximum soil particle size, and theminimum length greater than 5 times the maximum geosyn-thetic aperture size. The box shall allow for a minimum depthof 150 mm 6 in. above and below the geosynthetic. The depthof the soil in the box above or below the geosynthetic shall bea minimum of 6 times t
28、he D85 of the soil or 3 times themaximum particle size of the soil, whichever is greater. Thebox must allow for at least 305 mm 12 in. embedment lengthbeyond the load transfer sleeve.FIG. 1 Side View of Typical Test DeviceD7499/D7499M 09 (2014)2NOTE 1To remove side wall friction as much as possible
29、a highdensity polyethylene (HDPE) geomembrane should be bonded to theinside surfaces of the pullout box. The sidewalls may also be covered witha layer of silk fabric, which has been shown to eliminate adhesion and hasa very low friction value. Alternatively, a lubricant can be spread on thesidewalls
30、 of the box and thin sheets of polyethylene film used to minimizethe side wall friction. It should be also noted that the effect of sidewallfriction on the soil-geosynthetic interface can also be eliminated if aminimum distance is kept between the specimen and the side wall. Thisminimum distance is
31、recommended to be 150 mm 6 in.6.1.2 The box shall be fitted with a pair of metal sleeves(load transfer sleeves) at the entrance of the box to transfer theforce into the soil to a sufficient horizontal distance so as tosignificantly reduce the stress on the door of the box. Thesleeves shall consist o
32、f two tapered (illustrated in Fig. 3)ornon-tapered (no more than 13 mm 0.5 in. thick) platesextending the full width of the pullout box and into the pulloutbox a minimum distance of 150 mm 6 in., but it isrecommended that this distance equal the total soil depth aboveor below the geosynthetic. Both
33、design types must possesstapered edges at the point of load application in the soil that areno more then 3 mm 0.12 in. thick. The plates shall be rigidlyseparated at the sides with spacers and be sufficiently stiff suchthat normal stress is not transferred to the geosynthetic betweenthe plates.6.2 N
34、ormal Stress Loading DeviceNormal stress appliedto the upper layer of soil above the geosynthetic must beconstant and uniform for the duration of the load step. Tomaintain a uniform normal stress, a flexible pneumatic orhydraulic diaphragm-loading device which is continuous overthe entire test box a
35、rea should be used and capable ofmaintaining the applied normal stress within 62 % of therequired normal stress. Normal stresses utilized will depend ontesting requirements; however, stresses up to 250 kPa 35 psishould be anticipated. A recommended normal stress-loadingdevice is an air bag.6.3 Cycli
36、c Force Loading DeviceHorizontal cyclic forcemust be supplied by a device with the ability to apply cyclicload in the direction of the opening of the box. The force mustbe at the same level with the specimen.6.3.1 The cyclic force system must be able to apply multipleload repetitions using a haversi
37、ne-shaped load pulse consistingof a 0.2 s load followed by a 0.80 s rest period. The loadingsystem must also be able to simultaneously maintain a mini-mum seating load on the material during cyclic loading.6.3.2 Also, a device to measure the cyclic force (that is, aload cell) must be incorporated in
38、to the system and shall beaccurate within 60.5 % of its full-scale range.6.4 Displacement IndicatorsHorizontal displacement ofthe geosynthetic is measured at the entrance of the box and atseveral locations on the embedded portion of the specimen.Measurements outside the door at the box entrance are
39、made byelectronic displacement transducers (for example, linear vari-able differential transformers (LVDTs) can be used) mounted tothe box frame to read against a plate attached to the specimennear the door.6.4.1 Displacement measurements within the box may em-ploy any of several methods, which plac
40、e sensors or gaugeconnectors directly on the geosynthetic and monitor theirchange in location remotely. One such device utilizes wiregages, which are protected from normal stress by a surroundingtube, which runs from a location mounted on the specimen tothe outside of the box where displacements are
41、 measured bydisplacement transducers.6.4.2 All electronic measurement devices must be accurateto 60.01 mm. Locations of the devices must be accuratelydetermined and recorded. Minimum extension capabilities of50 mm 2 in. are recommended.6.4.3 Determine the displacement of the geosynthetic at thefront
42、 (leading end) and the rear (embedded end) of thegeosynthetic at several locations along its width; suggestedlayout is shown in Fig. 2.6.5 Geosynthetic Clamping DevicesClamps which con-nect the specimen to the cyclic force system without slipping,causing clamp breaks or weakening the material may be
43、 used,see Note 2. The clamps shall be swiveled to allow the cyclicforces to be distributed evenly throughout the width of thesample. The clamps must allow the specimen to remainhorizontal during loading and not interfere with the interfaceshear surface. Gluing, bonding, or otherwise molding of ageos
44、ynthetic within the clamp area is acceptable and recom-mended whenever slippage might occur. Thin metal rods ortubes may be used to reduce friction between the geosyntheticclamp/sample and the top edge of the lower load transfer sleeve(Fig. 3).NOTE 2A suggested method of clamping is shown in Fig. 4
45、andincludes a simple clamp consisting of two pieces of 22 gauge sheet metalglued to both sides of the geosynthetic sample. The sheet metal platesshould be at least the same width as the geosynthetic being tested. Specialprecautions should be taken to ensure that geotextile samples adhere to thesheet
46、 metalsuch as making holes for the epoxy to flow through the fabric,however; all such modifications to the fabric to facilitate bonding shouldnot interfere with the remainder of the geosynthetic protruding from thefront edge of the sheet metal.FIG. 2 Example Instrumentation LayoutD7499/D7499M 09 (20
47、14)36.6 Soil Preparation EquipmentUse equipment as neces-sary for the placement of soils at desired conditions. This mayinclude compaction devices such as vibratory or “jumping-jack” type compaction, or hand compaction hammers. Soilcontainer or hopper, leveling tools and soil placement/removaltools
48、may be required.6.7 Miscellaneous EquipmentMeasurement and trimmingequipment as necessary for geosynthetic preparation, a timingdevice and soil property testing equipment if desired.7. Geosynthetic Sampling7.1 Lot SampleDivide the product into lots and for any lotto be tested, take the lot samples a
49、s directed in Practice D4354,see Note 3.NOTE 3Lots of geosynthetics are usually designated by the producerduring manufacture. While this test method does not attempt to establisha frequency of testing for determination of design oriented data, the lotnumber of the laboratory sample should be identified. The lot numbershould be unique to the raw material and manufacturing process for aspecific number of units (for example, rolls, panel, etc.) designated by theproducer.7.2 Laboratory SampleConsider the units in the lotsample as
