1、Designation: D 5994 98(Reapproved 2003)Standard Test Method forMeasuring Core Thickness of Textured Geomembrane1This standard is issued under the fixed designation D 5994; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、 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 covers a procedure to measure the corethickness of textured geomembranes.1.2 This test method does
3、not provide thickness values forgeomembranes under variable normal stresses.2. Referenced Documents2.1 ASTM Standards:2D 4354 Practice for Sampling of Geosynthetics for TestingD 4439 Terminology for Geosynthetics3. Terminology3.1 Definitions:3.1.1 core thickness, nthe average thickness of a textured
4、geomembrane as measured using this particular test method.3.1.2 geomembrane, nan essentially impermeable geo-synthetic composed of one or more synthetic sheets. (D 4439)3.1.3 thickness gage points, nthe tips of a thickness gagewhich contact the upper and lower geomembrane surfaces, andbetween which
5、the thickness is measured.3.1.4 pressure, nthe force or load per unit area.3.1.5 textured geomembrane, na geomembrane havingone or both surfaces intentionally manufactured with projec-tions or indentations, most commonly for the purpose ofproviding increased shear strength against adjacent materials
6、.3.1.6 thickness, nthe perpendicular distance between onesurface and its opposite.3.1.7 For definitions of other terms relating to geomem-branes used in this test method, refer to the TerminologyD 4439.4. Summary of Test Method4.1 The core thickness of a textured geomembrane iscalculated as the aver
7、age value of measurements taken onreplicate specimens of the sample under investigation. Thethickness of each specimen is measured at a specific location asthe distance between two gage points. The opposing thicknessgage points are manufactured to a defined geometry, with aspecified force of 0.56 6
8、0.05 N (2.0 6 0.2 oz) applied alongtheir axis.5. Significance and Use5.1 Thickness is one of the basic index properties used tocontrol and track the quality of many geomembranes. Addi-tionally, many mechanical properties (for example, tensileyield strength, puncture strength, etc.) can be related to
9、 corethickness. Core thickness values may also be required incalculation of some parameters such as diffusion coefficients ortensile stresses.5.2 The measured core thickness of geomembranes mayvary considerably depending on the pressure applied to thespecimen during measurement. To reduce variation
10、in measure-ments and the chance of unrealistically low values due toexcessively high pressures, a specific gage point geometry andapplied force are prescribed in this test method.5.3 The test method is applicable to all commonly availabletextured geomembranes that are deployed as manufacturedgeomemb
11、rane sheets.6. Apparatus6.1 Thickness GageThe thickness gage shall be of thedead-weight type capable of measuring to an accuracy of atleast 60.01 mm (0.0004 in.). The gage shall be constructed topermit application of a specific force of 0.56 6 0.05 N(2.0 6 0.2 oz). The gage shall have a base point (
12、or anvil) anda free-moving presser point whose axes are aligned to eachother.NOTE 1The geomembrane specimen being measured should be main-tained perpendicular to the axes of the opposing gage points. Anunderlying support system may be necessary to support large testspecimens.6.2 Thickness Gage Point
13、sThe gage points shall be madeof hardened steel. The points shall be tapered at an angle of60 6 2 to the horizontal with the tip rounded to a radius of0.8 6 0.1 mm (0.031 6 0.004 in.). Fig. 1 shows the criticaldimensions.1This test method is under the jurisdiction of ASTM Committee D35 onGeosyntheti
14、cs and is the direct responsibility of Subcommittee D35.10 on Geomem-branes.Current edition approved May 10, 1998. Published January 1999. Originallyapproved in 1996. Last previous edition approved in 1998 as D 5994 982For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact AS
15、TM Customer 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.NOTE 2The gage and points ca
16、n be calibrated using standard thick-ness blocks. Frequent use and rough use of the gage can dull the gagepoints and cause misalignment, both of which will cause incorrectreadings. These problems can be detected by frequent calibration.7. Sampling7.1 SampleFor the sample, take a full width sample of
17、sufficient length so that the requirements of 7.2 through 7.4.2can be met. Exclude the inner and outer wraps of the roll or anymaterial not representative of the sample (see Note 1).7.2 Remove test specimens from the sample in a randomlydistributed pattern across the width. The thickness readingsmus
18、t include measurements within 15 cm (6 in.) of both edgesof the geomembrane roll.7.3 Test SpecimensFrom each unit in the sample, removethe specimens so that the edge of the specimen will extendbeyond the edge of the gage points by 10 mm (0.4 in.) in alldirections. It is recommended to use circular t
19、est specimens ofapproximately 75 mm (3 in.) diameter.7.4 Number of SpecimensUnless otherwise agreed upon,as when provided in an applicable material specification, takea number of test specimens per sample such that the user mayexpect, at the 95 % probability level, that the test result is notmore th
20、an 5 % of the average above or below the true averageof the sample. Determine the number of specimens per sampleas follows:7.4.1 Reliable Estimate of vWhen there is a reliableestimate of v based upon extensive sample records for similarmaterials tested in the users laboratory as directed in themetho
21、d, calculate the required number of specimens as fol-lows:n 5 tv/A!2(1)where:n = number of test specimens (rounded upward to a wholenumber),t = the value of Students “t” for one-sided limits (seeTable 1 in Test Method D 4354), a 95 % probabilitylevel, and the degrees of freedom associated with thees
22、timate of v,v = reliable estimate of the coefficient of variation ofindividual observations on similar materials in theusers laboratory under conditions of single-operationprecision, %, andA = 5 % of the average, the value of the allowable varia-tion.7.4.2 No Reliable Estimate of vWhen there is no r
23、eliableestimate of v for the users laboratory, Eq 1 should not be useddirectly. Instead, specify the fixed number ten of specimens.The number of specimens is calculated using v = 9.5 % of theaverage. These values for v are somewhat larger than usuallyfound in practice. When a reliable estimate of v
24、for the userslaboratory becomes available, Eq 1 will usually require fewerthan the fixed number of specimens.8. Conditioning8.1 Bring the specimens to a temperature equilibrium of21 6 2C (70 6 4F) and a relative humidity of 60 6 10 %.9. Procedure9.1 Test the conditioned specimens in the standard lab
25、ora-tory atmosphere specified in 8.1.9.2 With the specified force applied to the presser point onthe base point (that is, no specimen present), zero the measur-ing scale or record the initial non-zero reading.FIG. 1 Dead Weight Thickness Measurement Device for Textured GeomembranesD 5994 98 (2003)29
26、.3 Lift the presser point and insert the test specimen. Whileallowing the presser point to come slowly into contact with thetest specimen, adjust the test specimen to locate the gage pointsin the “low spots” or “valleys,” in between the projections, orinto the indentations, of the textured surface(s
27、) to obtain thelocal minimum thickness reading. Repeat the above so that atotal of three measurement readings are obtained for eachspecimen. Record only the lowest value of the three readings tothe nearest 0.025 mm or 0.001 in. as the thickness for thatspecimen.9.4 Allow the full dead weight pressur
28、e to be applied for 5s, and record the thickness value to the accuracy of the gage.9.5 Repeat the method for each of the remaining specimens.10. Calculation10.1 Calculate the average thickness of the sample from theindividual specimen results and record to the nearest 0.025 mmor 0.001 in.11. Report1
29、1.1 Report the following information for the averagethickness:11.1.1 Project, type of geomembrane tested, and method ofsampling.11.1.2 Name or description of thickness apparatus used fortesting.11.1.3 Dimensions of the gage points (if different than thisstandard).11.1.4 Dimensions of the sample and
30、test specimens (ifdifferent than this standard).11.1.5 Loading time interval.11.1.6 Number of specimens.11.1.7 Report the individual specimen thickness measure-ments to the nearest 0.025 mm or 0.001 in.11.1.8 Report the average thickness of the individual mea-surements to the nearest 0.025 mm or 0.0
31、01 in.11.1.9 Coefficient of variation of the individual measure-ments of the sample, in percent (optional).11.1.10 Any unusual or out-of-standard conditions or obser-vations made during the tests.12. Precision and Bias12.1 PrecisionThe precision of this test method procedureis being established.12.2
32、 BiasThe procedure in this test method has no biasbecause the value of average thickness can be defined only interms of this test method.13. Keywords13.1 geosynthetics; geomembrane; textured geomembrane;thicknessASTM International takes no position respecting the validity of any patent rights assert
33、ed in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by t
34、he responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive
35、 careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM Interna
36、tional, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 5994 98 (2003)3
