1、Designation: D6780 05 D6780/D6780M 12Standard Test Method forWater Content and Density of Soil in PlaceIn situ by TimeDomain Reflectometry (TDR)1This standard is issued under the fixed designation D6780;D6780/D6780M; the number immediately following the designation indicatesthe year of original adop
2、tion or, in the case 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. Scope*1.1 This test method may be used to determine the water content of soils an
3、d the in-place in situ density of soils using a TDRapparatus.1.2 This test method applies to soils that have 30 % or less by weight of their particles retained on the 19.0-mm (34-in.)-in.sieve.1.3 This test method is suitable for use as a means of acceptance for compacted fill or embankments.1.4 Thi
4、s test method may not be suitable for organic and highly plastic soils.1.5 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in PracticeD6026.1.5.1 The method used to specify how data are collected, calculated, or recorded in this stan
5、dard is not directly related to theaccuracy to which the data can be applied in design or other uses, or both. How one applies the results obtained using this standardis beyond its scope.1.6 Two alternative procedures are provided.1.6.1 Procedure A involves two tests in the field, an in-place in sit
6、u test and a test in a mold containing material excavated fromthe in-place in situ test location. The apparent dielectric constant is determined in both tests.1.6.2 Procedure B involves only an in-place in situ test by incorporating a bulk electrical conductivity the first voltage drop andlong term
7、voltage (V1 and Vf ) in addition to the apparent dielectric constant. While the bulk electrical conductivity can bedetermined from these measurements, it is not needed for the determination of water content and density.1.7 The values stated in either SI units or inch-pound units are to be regarded s
8、eparately as standard. The values stated in eachsystem may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from thetwo systems may result in non-conformance with the standard. For additional information consult SI10.1.8 This standard does n
9、ot purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards
10、:2D653 Terminology Relating to Soil, Rock, and Contained FluidsD698 Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort (12 400 ft-lbf/ft3 (600 kN-m/m3)D2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by MassD3740 Practice
11、for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used inEngineering Design and ConstructionD4753 Guide for Evaluating, Selecting, and Specifying Balances and Standard Masses for Use in Soil, Rock, and ConstructionMaterials Testing1 This test method is un
12、der the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.08 on Special and ConstructionControl Tests.Current edition approved May 1, 2005May 15, 2012. Published June 2005August 2012. Originally approved in 2002. Last previous edition approved i
13、n 20022005 asD6780 02.D6780 05. DOI: 10.1520/D6780-05.10.1520/D6780_D6780M-12.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page
14、on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that use
15、rs consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consho
16、hocken, PA 19428-2959. United States1D6026 Practice for Using Significant Digits in Geotechnical DataD6565 Test Method for Determination of Water (Moisture) Content of Soil by the Time-Domain Reflectometry (TDR) MethodE1 Specification for ASTM Liquid-in-Glass ThermometersSI10 Standard for Use of the
17、 International System of Units (SI): The Modern Metric System3. Terminology3.1 DefinitionsRefer to Terminology D653 for standard definitions of terms.3.2 Definitions of Terms Specific to This Standard:3.2.1 apparent dielectric constant, Kinsituin situ,Kmoldthe squared ratio of the velocity of light
18、in air to the apparent velocity ofelectromagnetic wave propagation in the soil measured by a TDR apparatus in placesitu and in the cylindrical mold, respectively.3.2.2 apparent length, laon a plot of electromagnetic wave signal versus scaled distance measured by a TDR apparatus asshown in Fig. 1, it
19、 is the horizontal distance between the point on the waveform due to the reflection from the surface of the soilwhere the probe is inserted into the soil to the point on the waveform due to the reflection from the end of the probe.3.2.3 bulk electrical conductivity, ECbECbelectrical conductivity is
20、a measure of how well a material accommodates thetransport of electric charge. Its SI derived unit is Siemens per meter (S/m). As an electromagnetic wave propagates along TDRprobed buried in soil, the signal energy is attenuated in proportion to the electrical conductivity along the travel path. Det
21、erminationof bulk electrical conductivity is illustrated in Fig. 1.3.2.4 coaxial head, CH3a device that forms a transition from the coaxial cable connected to the TDR apparatus to the MultipleRod Probe or to a Cylindrical Mold Probe.3.2.5 cylindrical mold probe, CMP3a probe formed by a cylindrical m
22、etal mold as the outer conductor having a non-metallicend plate, filled with compacted soil, and with an inner conductor consisting of a rod driven into the soil along the axis of the mold.3.2.6 first voltage drop, V1it is the vertical distance (voltage) between the point on the waveform due to the
23、reflection fromthe surface of the soil where the probe is inserted into the soil to the point on the waveform due to the reflection from the end ofthe probe, as illustrated in Fig. 1.3.2.7 long term voltage, Vfthe long term voltage as illustrated in Fig. 1.3 The apparatus is covered by patents. Inte
24、rested parties are invited to submit information regarding the identification of alternative(s) to this patented item to the ASTMHeadquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee,1 which you may attend.FIG. 1 Typical TDR Waveform for S
25、oil Showing Measurements to Obtain Apparent Dielectric Constant, Ka, andBulk D.C. Electrical Conductivity, ECb, First Voltage Drop, V1, and Long Term Voltage, Vf .D6780/D6780M 1223.2.8 multiple rod probe, MRP3a probe formed by driving four rods of equal length into the soil in a pattern where three
26、ofthe rods define the outer conductor of a “coaxial cable” and one of the rods is the inner conductor.3.2.9 probe length, Lthe length of the TDR probe that is below the surface of the soil.3.2.10 scaled distance, lthe product of the velocity of light in air and electromagnetic wave travel time in th
27、e soil divided bytwo.3.2.9 TDR internal resistance, Rsthe internal resistance of the TDRs pulse generator (generally 50 ohms).3.2.11 voltage source,source voltage, Vsthe source voltage and equal to twice the step voltage generated by the TDR.3.2.12 voltage, long term, VTDR internal resistance, Rfsth
28、e long term voltage as illustrated ininternal resistance of the TDRspulse Fig. 1.generator (generally 50 ohms).4. Summary of Test Method4.1 Procedure AA4The dielectric constant of the soil in-place in situ is determined using a multiple rod probe(MRP),(MRP), a coaxial head (CH),(CH), and TDR apparat
29、us. The soil at the location of the insitu in situ measurement is thenexcavated and compacted in a mold. By measurement of the mass of the mold and soil and with the mass and volume of the moldknown, the wet density of the soil in the mold is determined. A rod driven into the soil along the axis of
30、the mold creates acylindrical mold probe (CMP).(CMP). Using the same coaxial head (CH),(CH), an adapter ring, and the TDR apparatus thedielectric constant of the soil in the mold is measured. The water content of the soil in the mold is determined using a correlationbetween the dielectric constant,
31、moisture content and soil density. The correlation requires two constants that are somewhat soilspecific. It is assumed that the water content of the soil in placesitu is the same as the water content in the mold. The density ofthe soil in placesitu is determined from the density of the soil in the
32、mold and the dielectric constants measured in the mold andin place.situ.4.2 Procedure BB4The apparent dielectric constant and the bulk electrical conductivity of the soil in-place is in situ, firstvoltage drop and long term voltage (V1 and Vf) are determined using a multiple rod probe (MRP),(MRP), a
33、 coaxial head (CH),(CH),and TDR apparatus. The water content and density of the soil in-place in situ are determined from the measured apparent dielectricconstant, theV1,Vf bulk electrical conductivity and sixand five constants. The sixfive soil constants are soil and in-place in situ porefluid depe
34、ndent. The sixfive soil constants are determined in conjunction with laboratory compaction procedures using specifiedcompaction procedures, for example, Test Method D698, and by taking measurements of the apparent dielectric constant, V1 andtheVf bulk electrical conductivity for each compaction poin
35、t.5. Significance and Use5.1 This test method can be used to determine the density and water content of naturally occurring soils and of soils placedduring the construction of earth embankments, road fills, and structural backfills.5.2 Time domain reflectometry (TDR) measures the apparent dielectric
36、 constant (Procedure A) and both the apparent dielectricconstant and the bulk electrical conductivityconstant, first voltage drop and long term voltage (V1 and Vf) (Procedure B) of soil.The apparent dielectric constant is affected significantly by the water content and density of soil, and to a less
37、er extent by thechemical composition of soil and pore water, and by temperature. The bulk electrical conductivity is first voltage drop and longterm voltage (V1 and Vf) are affected significantly by the water content, density, and the chemical composition of the in-place insitu pore water, and to a
38、lesser extent the chemical composition of the soil solids. This test method measures the gravimetric watercontent and makes use of a different relationship between the electrical properties and water content from Test Method D6565which measures the volumetric water content.5.3 Soil and pore water ch
39、aracteristics are accounted for in Procedure A with two calibration constants and for Procedure B withsixfive calibration constants. The two soil constants for Procedure A are determined for a given soil by performing compaction testsin a special mold as described in Annex A2. The sixfive soil const
40、ants for Procedure B are determined in conjunction withcompaction testing in accordance with specified compaction procedures, for example, Test Method D698 as described in AnnexA3. Both Procedures A and B use Test Method D2216 to determine the water contents.5.4 When following Procedure A, the water
41、 content is the average value over the length of the cylindrical mold and the densityis the average value over the length of the multiple-rod probe embedded in the soil. When following Procedure B, the water contentand density is the average values over the length of the multiple-rod embedded in the
42、 soil.NOTE 1The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of theequipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objectivetesting
43、/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliableresults depend on many factors; Practice D3740 provides a means of evaluating some of those factors.4 The apparatus and procedures are covered by pat
44、ents and pending patents. Interested parties are invited to submit information regarding the identification of alternative(s)to these patented items to the ASTM Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee,1 which you mayattend.D6
45、780/D6780M 1236. Interferences6.1 Quality and accuracy of the test results significantly depend on soil having contact with the inner conductor of the probes.To assist this, when installing the rods of the MRP, the rod that forms the inner conductor must be the last rod installed. If in theinstallat
46、ion process, the rod hits upon a large particle that causes it to drift from vertical alignment, all rods should be removedand the test conducted in a new location at least 0.2-m (8-in.)8-in. from the previous test location.6.2 The quality of the signal read by the TDR apparatus depends on having cl
47、ean contacts between the CH and the MRP andthe CMP. The contacting surfaces should be wiped with a clean cloth prior to placing the CH on the MRP and the CMP. Onceplaced, observe the signal on the TDR apparatus. If the characteristic signal is not present, the CH may have to be slightly rotatedabout
48、 its axis to make better contact.6.3 This test method only applies to non-frozen soil. The apparent dielectric constant is slightly temperature dependent for soilsand depends on soil type. For soil temperatures between 15C and 25C (59F59F and 77F),77F, no temperature correctionsare needed for most s
49、oils. A simple temperature adjustment for water content determination is part of the test method.7. Apparatus7.1 TDR Apparatus, a Metallic Time Domain Reflectometer with a scaled length resolution of at least 2.4-mm (0.10-in.)0.10-in. (this corresponds approximately to a time between data points less than or equal to sixteen picoseconds (16 10-12 s). Aportable computer with a communication port to the TDR is suggested for controlling the apparatus, acquiring and saving the data,and for making the calculations as the test proceeds.7.2 Mul
