1、Designation: D 7499/D7499M 09Standard Test Method forMeasuring Geosynthetic-Soil Resilient Interface ShearStiffness1This standard is issued under the fixed designation D 7499/D7499M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision,
2、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 determine the a
3、pparentstiffness 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 method was develope
4、d 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 different geosynthe
5、tics, 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 used independent
6、ly 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-priate safety and hea
7、lth 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:2D 123 Terminology Relating to TextilesD 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 3080 Test
8、 Method for Direct Shear Test of Soils UnderConsolidated Drained ConditionsD 4439 Terminology for GeosyntheticsD 4354 Practice for Sampling of Geosynthetics for Testing3. Terminology3.1 For definitions of other terms used in this test methodrefer to Terminologies D 123, D 653, and D 4439.3.2 Definit
9、ions 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 21 6 2C (70 6 4F).3.2.3 cross-machine direction, nthe dire
10、ction 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 frompolymeric material used with soil, rock, earth, or o
11、ther 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 the soil and the geosynthetic determined bycalculating
12、 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 machine direction, nthe direction in the plane of thegeosy
13、nthetic 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 uniform over the entire embeddedlength.1This test meth
14、od 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 June 15, 2009. Published September 2009.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM C
15、ustomer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.10 pullout force, (kN), , nf
16、orce required to pull ageosynthetic out of the soil during a pullout test.3.2.11 pullout resistance, (kN/m), nthe pullout force perwidth 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
17、direction asmanufactured.3.2.13 wire gage, na displacement gage consisting of anon extensible wire attached to the geosynthetic and 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 geosynthet
18、ic isembedded between two layers of soil. Six prescribed levels ofhorizontal cyclic force are applied to the geosynthetic at fivespecified levels of normal stress confinement. The maximumand minimum forces and corresponding displacements arerecorded for the last ten cycles of each combination of nor
19、malstress and cyclic force (loading sequence).4.2 The resilient interface shear stiffness (kPa/m or psi/in)of the test specimen can be calculated for any loading sequenceby dividing the cyclic shear stress by the corresponding netrecoverable horizontal displacement of the embedded geosyn-thetic5. Si
20、gnificance and Use5.1 This test method is intended as a performance test toprovide the user with a set of design values for the testconditions 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, whic
21、h can be usedin the design of geosynthetic-reinforced pavement structures orin applications where geosynthetics are subjected to cyclicloads.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 Informa
22、tion derived from this test may be a function ofsoil gradation, plasticity, as-placed dry unit weight, moisturecontent, length and surface characteristics of the geosyntheticand other test parameters. Therefore, results are expressed interms of the actual test conditions. The test measures the netef
23、fect of a combination of interface shear mechanisms, whichmay vary depending on type of geosynthetic specimen, em-bedment length, 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
24、, comparative tests to determine ifthere is a statistical bias between laboratories may be advis-able.6. Apparatus6.1 Test BoxAn open 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 fronta
25、s 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 with mini-mum dimensions 457 mm (18 in.) long by 457 mm (18 in.)wide by 305 mm (12 in.) deep, if sidewall friction is mini-mized, otherwise the minimum width should be 76
26、0 mm (30in.). The dimensions should be increased, if necessary, so thatminimum width is the greater of 20 times the D85 of the soilor 6 times the maximum soil particle size, and the minimumlength greater than 5 times the maximum geosynthetic aperturesize. The box shall allow for a minimum depth of 1
27、50 mm (6in.) above and below the geosynthetic. The depth of the soil inthe box above or below the geosynthetic shall be a minimum of6 times the D85 of the soil or 3 times the maximum particlesize of the soil, whichever is greater. The box must allow for atleast 305 mm (12 in.) embedment length beyon
28、d the loadtransfer sleeve.NOTE 1To remove side wall friction as much as possible 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
29、very low friction value. Alternatively, a lubricant can be spread on theFIG. 1 Side View of a Typical Test DeviceD 7499/D7499M 092sidewalls 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-
30、geosynthetic interface can also be eliminated if aminimum distance is kept between the specimen and the side wall. Thisminimum distance is 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 theforc
31、e into the soil to a sufficient horizontal distance so as tosignificantly reduce the stress on the door of the box. Thesleeves shall consist of 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 pullou
32、tbox a minimum distance of 150 mm (6 in.), but it isrecommended that this distance equal the total soil depth aboveor below the geosynthetic. Both 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 rigid
33、lyseparated at the sides with spacers and be sufficiently stiff suchthat normal stress is not transferred to the geosynthetic betweenthe plates.6.2 Normal Stress Loading Device Normal stress appliedto the upper layer of soil above the geosynthetic must beconstant and uniform for the duration of the
34、load step. Tomaintain a uniform normal stress, a flexible pneumatic orhydraulic diaphragm-loading device which is continuous overthe entire test box area should be used and capable ofmaintaining the applied normal stress within 62% of therequired normal stress. Normal stresses utilized will depend o
35、ntesting requirements; however, stresses up to 250 kPa (35 psi)should be anticipated. A recommended normal stress-loadingdevice is an air bag.6.3 Cyclic Force Loading Device Horizontal cyclicforce must be supplied by a device with the ability to applycyclic load in the direction of the opening of th
36、e box. The forcemust be at the same level with the specimen.6.3.1 The cyclic force system must be able to apply multipleload repetitions using a haversine-shaped load pulse consistingof a 0.2 second load followed by a 0.80 second rest period. Theloading system must also be able to simultaneously mai
37、ntain aminimum seating load on the material during cyclic loading.6.3.2 Also, a device to measure the cyclic force (i.e., a loadcell) must be incorporated into the system and shall be accuratewithin 60.5 % of its full-scale range.6.4 Displacement Indicators Horizontal displacementof the geosynthetic
38、 is measured at the entrance of the box andat several locations on the embedded portion of the specimen.Measurements outside the door at the box entrance are made byelectronic displacement transducers (e.g., linear variable dif-ferential transformers (LVDTs) can be used) mounted to thebox frame to r
39、ead against a plate attached to the specimen nearthe door.6.4.1 Displacement measurements within the box may em-ploy any of several methods, which place sensors or gaugeconnectors directly on the geosynthetic and monitor theirchange in location remotely. One such device utilizes wiregages, which are
40、 protected from normal stress by a surroundingtube, which runs from a location mounted on the specimen tothe outside of the box where displacements are measured bydisplacement transducers.6.4.2 All electronic measurement devices must be accurateto 6 0.01 mm. Locations of the devices must be accurate
41、lydetermined and recorded. Minimum extension capabilities of50 mm (2 in.) are recommended.6.4.3 Determine the displacement of the geosynthetic at thefront (leading end) and the rear (embedded end) of thegeosynthetic at several locations along its width; suggestedlayout is shown in Fig. 26.5 Geosynth
42、etic Clamping DevicesClamps which con-nect the specimen to the cyclic force system without slipping,causing clamp breaks or weakening the material may be used,see Note 2. The clamps shall be swiveled to allow the cyclicforces to be distributed evenly throughout the width of thesample. The clamps mus
43、t allow the specimen to remainhorizontal during loading and not interfere with the interfaceshear surface. Gluing, bonding, or otherwise molding of ageosynthetic within the clamp area is acceptable and recom-mended whenever slippage might occur. Thin metal rods ortubes may be used to reduce friction
44、 between the geosyntheticclamp/sample and the top edge of the lower load transfer sleeve(Fig. 3).NOTE 2 A suggested method of clamping is shown in Fig. 4 andincludes a simple clamp consisting of two pieces of 22 gauge sheet metalglued to both sides of the geosynthetic sample. The sheet metal platess
45、hould be at least the same width as the geosynthetic being tested. Specialprecautions should be taken to ensure that geotextile samples adhere to thesheet metal such as making holes for the epoxy to flow through thefabric, however; all such modifications to the fabric to facilitate bondingshould not
46、 interfere with the remainder of the geosynthetic protrudingfrom the front edge of the sheet metal.6.6 Soil Preparation Equipment Use 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 h
47、and compaction hammers. SoilFIG. 2 Example Instrumentation LayoutD 7499/D7499M 093container or hopper, leveling tools and soil placement/removaltools may be required.6.7 Miscellaneous Equipment Measurement and trim-ming equipment as necessary for geosynthetic preparation, atiming device and soil pro
48、perty testing equipment if desired.7. Geosynthetic Sampling7.1 Lot SampleDivide the product into lots and for any lotto be tested, take the lot samples as directed in Practice D 4354,see Note 3NOTE 3Lots of geosynthetics are usually designated by the producerduring manufacture. While this test metho
49、d 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 the units in the laboratory sample for the lot to betested. Take for a laboratory sample, a sample extending thefull width of the geosynthetic production unit, of suffici
