1、Designation: D 6780 05Standard Test Method forWater Content and Density of Soil in Place by Time DomainReflectometry (TDR)1This standard is issued under the fixed designation D 6780; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、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. Scope*1.1 This test method may be used to determine the watercontent of soils and the in-place density of soils us
3、ing a TDRapparatus.1.2 This test method applies to soils that have 30 % or lessby weight of their particles retained on the 19.0-mm (34-in.)sieve.1.3 This test method is suitable for use as a means ofacceptance for compacted fill or embankments.1.4 This test method may not be suitable for organic an
4、dhighly plastic soils.1.5 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D 6026.1.5.1 The method used to specify how data are collected,calculated, or recorded in this standard is not directly related tothe accuracy to whi
5、ch the data can be applied in design or otheruses, or both. How one applies the results obtained using thisstandard is beyond its scope.1.6 Two alternative procedures are provided.1.6.1 Procedure A involves two tests in the field, an in-placetest and a test in a mold containing material excavated fr
6、om thein-place test location. The apparent dielectric constant isdetermined in both tests.1.6.2 Procedure B involves only an in-place test by incor-porating a bulk electrical conductivity in addition to theapparent dielectric constant.1.7 The values stated in either SI units or inch-pound unitsare t
7、o be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard. For additional information consult ASTMSI 101.8 Thi
8、s 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 health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Document
9、s2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 698 Test Methods for Moisture-Density Relations ofSoils and Soil-Aggregate Mixtures, Using 5.5 lb (2.49 kg)Rammer and 12-in. (305-mm) DropD 2216 Method for Laboratory Determination of Water(Moisture) Content of Soil,
10、 Rock, and Soil-AggregateMixturesD 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and ConstructionD 4753 Specification for Evaluating, Selecting, and Speci-fying Balances and Scales for Use in Soil and RockTes
11、tingD 6026 Practice for Using Significant Digits in Geotechni-cal DataD 6565 Test Method for Determination of Water (Moisture)Content of Soil by the Time Domain ReflectometryMethodE1 Specification for ASTM ThermometersSI 10 Standard for Use of the International System of Units(SI): The Modern Metric
12、 System3. Terminology3.1 DefinitionsRefer to Terminology D 653 for standarddefinitions of terms.3.2 Definitions of Terms Specific to This Standard:3.2.1 apparent dielectric constant, Kinsitu, Kmoldthesquared ratio of the velocity of light in air to the apparentvelocity of electromagnetic wave propag
13、ation in the soilmeasured by a TDR apparatus in place and in the cylindricalmold, respectively.3.2.2 apparent length, laon a plot of electromagneticwave signal versus scaled distance measured by a TDR1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct r
14、esponsibility of Subcommittee D18.08 on Special andConstruction Control Tests.Current edition approved May 1, 2005. Published June 2005. Originallyapproved in 2002. Last previous edition approved in 2002 as D 6780 02.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact AST
15、M Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consho
16、hocken, PA 19428-2959, United States.apparatus as shown in Fig. 1, it is the horizontal distancebetween the point on the waveform due to the reflection fromthe surface of the soil where the probe is inserted into the soilto the point on the waveform due to the reflection from the endof the probe.3.2
17、.3 bulk electrical conductivity, ECbelectrical conduc-tivity is a measure of how well a material accommodates thetransport of electric charge. Its SI derived unit is Siemens permeter (S/m). As an electromagnetic wave propagates alongTDR probed buried in soil, the signal energy is attenuated inpropor
18、tion to the electrical conductivity along the travel path.Determination of bulk electrical conductivity is illustrated inFig. 1.3.2.4 coaxial head, CH3a device that forms a transitionfrom the coaxial cable connected to the TDR apparatus to theMultiple Rod Probe or to a Cylindrical Mold Probe.3.2.5 c
19、ylindrical mold probe, CMP3a probe formed by acylindrical metal mold as the outer conductor having a non-metallic end plate, filled with compacted soil, and with an innerconductor consisting of a rod driven into the soil along the axisof the mold.3.2.6 multiple rod probe, MRP3a probe formed by drivi
20、ngfour rods of equal length into the soil in a pattern where threeof the rods define the outer conductor of a “coaxial cable” andone of the rods is the inner conductor.3.2.7 probe length, Lthe length of the TDR probe that isbelow the surface of the soil.3.2.8 scaled distance, lthe product of the vel
21、ocity of lightin air and electromagnetic wave travel time in the soil dividedby two.3.2.9 TDR internal resistance, Rsthe internal resistance ofthe TDRs pulse generator (generally 50 ohms).3.2.10 voltage source, Vsthe source voltage and equal totwice the step voltage generated by the TDR.3.2.11 volta
22、ge, long term, Vfthe long term voltage asillustrated in Fig. 1.4. Summary of Test Method4.1 Procedure AThe dielectric constant of the soil in-place is determined using a multiple rod probe (MRP), acoaxial head (CH), and TDR apparatus. The soil at the locationof the insitu measurement is then excavat
23、ed and compacted ina mold. By measurement of the mass of the mold and soil andwith the mass and volume of the mold known, the wet densityof the soil in the mold is determined. A rod driven into the soilalong the axis of the mold creates a cylindrical mold probe(CMP). Using the same coaxial head (CH)
24、, an adapter ring, andthe TDR apparatus the dielectric constant of the soil in themold is measured. The water content of the soil in the mold isdetermined using a correlation between the dielectric constant,moisture content and soil density. The correlation requires twoconstants that are somewhat so
25、il specific. It is assumed that thewater content of the soil in place is the same as the watercontent in the mold. The density of the soil in place isdetermined from the density of the soil in the mold and thedielectric constants measured in the mold and in place.4.2 Procedure BThe apparent dielectr
26、ic constant and thebulk electrical conductivity of the soil in-place is determinedusing a multiple rod probe (MRP), a coaxial head (CH), andTDR apparatus. The water content and density of the soilin-place are determined from the measured apparent dielectricconstant, the bulk electrical conductivity
27、and six constants. Thesix soil constants are soil and in-place pore fluid dependent.The six soil constants are determined in conjunction withlaboratory compaction procedures using specified compaction3The apparatus is covered by patents. Interested parties are invited to submitinformation regarding
28、the identification of alternative(s) to this patented item to theASTM Headquarters.Your comments will receive careful consideration at a meetingof the responsible technical committee, which you may attend.FIG. 1 Typical TDR Waveform for Soil Showing Measurements to Obtain Apparent Dielectric Constan
29、t, Ka, andBulk D.C. Electrical Conductivity, ECbD6780052procedures, for example, Test Method D 698, and by takingmeasurements of the apparent dielectric constant and the bulkelectrical conductivity for each compaction point.5. Significance and Use5.1 This test method can be used to determine the den
30、sityand water content of naturally occurring soils and of soilsplaced during the construction of earth embankments, roadfills, and structural backfills.5.2 Time domain reflectometry (TDR) measures the appar-ent dielectric constant (Procedure A) and both the apparentdielectric constant and the bulk e
31、lectrical conductivity (Proce-dure B) of soil. The apparent dielectric constant is affectedsignificantly by the water content and density of soil, and to alesser extent by the chemical composition of soil and porewater, and by temperature. The bulk electrical conductivity isaffected significantly by
32、 the water content, density, and thechemical composition of the in-place pore water, and to a lesserextent the chemical composition of the soil solids. This testmethod measures the gravimetric water content and makes useof a different relationship between the electrical properties andwater content f
33、rom Test Method D 6565 which measures thevolumetric water content.5.3 Soil and pore water characteristics are accounted for inProcedure A with two calibration constants and for ProcedureB with six calibration constants. The soil constants for Proce-dure A are determined for a given soil by performin
34、g compac-tion tests in a special mold as described in Annex A2. The sixsoil constants for Procedure B are determined in conjunctionwith compaction testing in accordance with specified compac-tion procedures, for example, Test Method D 698 as describedin Annex A3. Both Procedures A and B use Test Met
35、hodD 2216 to determine the water contents.5.4 When following Procedure A, the water content is theaverage value over the length of the cylindrical mold and thedensity is the average value over the length of the multiple-rodprobe embedded in the soil. When following Procedure B, thewater content and
36、density is the average values over the lengthof the multiple-rod embedded in the soil.NOTE 1The quality of the result produced by this standard isdependent on the competence of the personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Pra
37、ctice D 3740 are generally considered capable of competentand objective testing/sampling/inspection/etc. Users of this standard arecautioned that compliance with Practice D 3740 does not in itself assurereliable results. Reliable results depend on many factors; Practice D 3740provides a means of eva
38、luating some of those factors.6. Interferences6.1 Quality and accuracy of the test results significantlydepend on soil having contact with the inner conductor of theprobes. To assist this, when installing the rods of the MRP, therod that forms the inner conductor must be the last rodinstalled. If in
39、 the installation process, the rod hits upon a largeparticle that causes it to drift from vertical alignment, all rodsshould be removed and the test conducted in a new location atleast 0.2-m (8-in.) from the previous test location.6.2 The quality of the signal read by the TDR apparatusdepends on hav
40、ing clean contacts between the CH and theMRP and the CMP. The contacting surfaces should be wipedwith a clean cloth prior to placing the CH on the MRP and theCMP. Once placed, observe the signal on the TDR apparatus.If the characteristic signal is not present, the CH may have tobe slightly rotated a
41、bout its axis to make better contact.6.3 This test method only applies to non-frozen soil. Theapparent dielectric constant is slightly temperature dependentfor soils and depends on soil type. For soil temperaturesbetween 15C and 25C (59F and 77F), no temperaturecorrections are needed for most soils.
42、 A simple temperatureadjustment for water content determination is part of the testmethod.7. Apparatus7.1 TDR Apparatus, a Metallic Time Domain Reflectometerwith a scaled length resolution of at least 2.4-mm (0.10-in.)(this corresponds approximately to a time between data pointsless than or equal to
43、 sixteen picoseconds (16 3 10-12s). Aportable computer with a communication port to the TDR issuggested for controlling the apparatus, acquiring and savingthe data, and for making the calculations as the test proceeds.7.2 Multiple Rod Probe (MRP)3with Coaxial Head (CH)37.2.1 The MRP consists of four
44、 common steel spikes,typically 250-mm (10-in.) in length and uniform diameters of9.5-mm (38-in.). (Other length spikes, but with the samediameter, may be used but in no case should they have lengthsless than 150-mm (6-in.). For lengths longer than 250-mm(10-in.), drift in the alignment of the spikes
45、 and loss ofreflected signal from the end of the MRP may occur.)7.2.2 AMRPguide template (see Fig. 2) is used to guide thespikes as they are driven into the soil. The template must allowfor its removal after the spikes are driven and before a TDRmeasurement is made. (The radius from the central spik
46、e to theouter spikes must be within the range of 5 to 7.5 times thediameter of the central spike.)7.2.3 The Coaxial Head (CH)3(see Fig. 3) forms a transi-tion from the coaxial cable coming from the TDR apparatus tothe MRP.7.3 Cylindrical Mold Probe (CMP)3, the CMP consists of acylindrical mold, a gu
47、ide template, a central rod, and a ringcollar. Details for these items are shown in Fig. 4.7.3.1 The central rod is a stainless steel rod with a diameterof 8.0-mm (516-in.) and a length of 264-mm (10.4-in.) inlength.7.4 Balances or Scales, meeting Specification GP10 ofSpecification D 4753 to determi
48、ne the mass of the soil and thecylindrical mold. A battery-operated balance or scale having aminimum capacity of 10 kg is suitable when an apparatus withthe dimension given in Fig. 3 is used.7.5 Driving Tools, a brass-headed hammer for drivingspikes for the MRP and the central rod into the cylindric
49、almold.Aresin-headed hammer also may be used for driving thecentral rod into the cylindrical mold. (Use of these hammersprevents peening of the driving end of the steel rods fromrepeated use.)7.6 Tamping Rod, an aluminum rod with flat ends, adiameter of 37-mm (1.5-in.), and a length of 380-mm (15-in.).Other tamping devices which provide a relatively uniformlycompacted specimen also may be used.D67800537.7 Thermometer, 0 to 50C range, 0.5C graduations,conforming to requirements of Specification E1.7.8 Vernier or Dial Caliper, having a measuring range of atleas
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1