1、Designation: D7698 11aStandard Test Method forIn-Place Estimation of Density and Water Content of Soiland Aggregate by Correlation with Complex ImpedanceMethod1This standard is issued under the fixed designation D7698; the number immediately following the designation indicates the year oforiginal ad
2、option or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 Purpose and Application1.1.1 This test method describes the procedure,
3、 equipment,and interpretation methods for estimating in-place soil drydensity and water content using a Complex-Impedance Mea-suring Instrument (CIMI).1.1.2 CIMI measurements as described in this Standard TestMethod are applicable to measurements of compacted soilsintended for roads and foundations.
4、1.1.3 This test method describes the procedure for estimat-ing in-place density and water content of soils and soil-aggregates by use of a CIMI. The electrical properties of soilare measured using a radio frequency voltage applied to soilelectrical probes driven into the soils and soil-aggregates to
5、 betested, in a prescribed pattern and depth. Certain algorithms ofthese properties are related to wet density and water content.This correlation between electrical measurements, and densityand water content is accomplished using a calibration method-ology. In the calibration methodology, density an
6、d watercontent are determined by other ASTM Test Standards thatmeasure soil density and water content, thereafter correlatingthe corresponding measured electrical properties to the soilphysical properties.1.1.4 The values stated in SI units are to be regarded asstandard. The inch-pound units given i
7、n parentheses aremathematical conversions which are provided for informationpurposes only and are not considered standard.1.1.5 All observed and calculated values shall conform tothe guidelines for significant digits and rounding established inPractice D6026 unless superseded by this standard.1.2 Ge
8、neralized Theory1.2.1 Two key electrical properties of soil are conductivityand relative dielectric permittivity which are manifested as avalue of complex-impedance that can be determined.1.2.2 The soil conductivity contributes primarily to the realcomponent of the complex-impedance, and the soil re
9、lativedielectric permittivity contributes primarily to the imaginarycomponent of the complex-impedance.1.2.3 The complex-impedance of soil can be determined byplacing two electrodes in the soil to be tested at a knowndistance apart and a known depth. The application of a knownfrequency of alternatin
10、g current to the electrodes enables ameasurement of current through the soil, voltage across theelectrodes, and the electrical phase difference between thevoltage and current waves. Complex-impedance is calculatedfrom these known and measured parameters.1.2.4 From the determined complex-impedance, a
11、n electri-cal network consisting of a resistor (R) and capacitor (C)connected in parallel are used to represent a model of the soilbeing tested.1.2.5 Relationships can be made between the soil wetdensity and the magnitude of the complex-impedance, and alsobetween the soil water mass per unit measure
12、d, and thequotient of the values of C and R using a Soil Model process.1.2.6 The Soil Model process results in mathematical rela-tionships between the physical and electrical characteristics ofthe soil which are used for soil-specific calibration of the CIMI.1.2.7 Refer to Appendix X1 for a more det
13、ailed explanationof complex-impedance measurement of in-place soil, and itsuse in field measurements for the estimation of dry density andwater content.1.3 Precautions1.3.1 The radio frequencies and output power levels of theCIMI method are such that they are harmless according to theFederal Communi
14、cations Commission (FCC).1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.08 on Special andConstruction Control Tests.Current edition approved Nov. 1, 2011. Published January 2012. Originallyapproved in 2011. Last p
15、revious edition approved in 2011 as D769811. DOI:10.1520/D7698-11a.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1.3.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is ther
16、esponsibility 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 Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluidsD698 Test Methods for Labora
17、tory Compaction Character-istics of Soil Using Standard Effort (12 400 ft-lbf/ft3(600kN-m/m3)D1556 Test Method for Density and Unit Weight of Soil inPlace by Sand-Cone MethodD1557 Test Methods for Laboratory Compaction Charac-teristics of Soil Using Modified Effort (56,000 ft-lbf/ft3(2,700 kN-m/m3)D
18、2216 Test Methods for Laboratory Determination of Wa-ter (Moisture) Content of Soil and Rock by MassD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4253 Test Methods for Maximum Index Density and
19、UnitWeight of Soils Using a Vibratory TableD4643 Test Method for Determination of Water (Moisture)Content of Soil by Microwave Oven HeatingD4718 Practice for Correction of Unit Weight and WaterContent for Soils Containing Oversize ParticlesD4944 Test Method for Field Determination of Water(Moisture)
20、 Content of Soil by the Calcium Carbide GasPressure TesterD6026 Practice for Using Significant Digits in GeotechnicalDataD7382 Test Methods for Determination of Maximum DryUnit Weight and Water Content Range for EffectiveCompaction of Granular Soils Using a Vibrating Hammer3. Terminology3.1 Definiti
21、ons shall be in accordance with the terms andsymbols given in Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 complex impedance, nthe ratio of the phasor equiva-lent of a steady-state sine-wave or voltage like quantity(driving force) to the phasor equivalent of a steady-sta
22、tesine-wave current of current like quantity (response) (1) .Inpractice, CIMI uses the magnitude of the impedance ratio (|Z|)in its calculations.3.2.2 dielectric properties, nsee relative dielectric permit-tivity and dielectric phase angle.3.2.2.1 dielectric phase angle, nthe angular difference inph
23、ase between the sinusoidal alternating voltage applied to adielectric and the component of the resulting alternatingcurrent having the same period as the voltage.3.2.2.2 relative dielectric permittivity, nthe property thatdetermines the electrostatic energy stored per unit volume forunit potential g
24、radient multiplied by the permittivity of freespace (2).3.2.3 phase relationship, nthe electrical phase differencebetween the applied probe-to-probe radio frequency voltage,and the resulting soil current.3.2.4 probe-to-probe voltage, nthe peak value of radiofrequency voltage measured across two prob
25、es that are con-ducting soil current.3.2.5 radio frequency, na frequency useful for radiotransmission (1).33.2.6 soil capacitance, nthe value of the capacitor in anequivalent parallel resistor-capacitor circuit that results fromthe probe-to-probe voltage, soil current, and resulting phaserelationshi
26、p due to the application of a radio frequencyalternating voltage source applied to the probes.3.2.7 soil current , nthe peak value of the radio frequencycurrent passing through the soil from one probe electrode toanother.3.2.8 Soil Model, nthe result of a calibration procedurethat establishes a corr
27、elating linear function between measuredelectrical soil properties and measured physical soil properties.3.2.9 Soil Model linear correlation function, none of thetwo mathematical expressions that are derived from perform-ing linear regressions on two sets of soil test data; measuredphysical soil cha
28、racteristics, and a corresponding set of elec-trical measurements made on the soil samples.3.2.10 soil resistance, nthe value of the resistor in anequivalent parallel resistor-capacitor circuit that results fromthe probe-to-probe voltage, soil current, and resulting phaserelationship due to the appl
29、ication of a radio frequencyalternating voltage source applied to the probes.3.2.11 water mass per unit volume, nthe mass of watercontained in a volume of soil being measured, and is expresseddimensionally as kg/m3.4. Summary of the Test Method4.1 The test method is a two step process.4.1.1 A Soil M
30、odel that relates impedance measurement tothe density and water content of the soil is developed. In thisstep the electrical measurements are collected at locations thathave various water contents and densities typical of the rangeto be expected. Concurrent with collecting the electrical data,determ
31、ination of density and water content are performed at thesame locations using one or more of the traditional testmethods, such as Test Methods D1556 and D2216. The processis repeated over the site sufficiently that a range of watercontents and densities are obtained. The combined data (im-pedance an
32、d density/water content) will generate the correlat-ing linear regression functions of the Soil Model.4.1.2 Once the Soil Model has been developed the CIMIdevice is used to make electrical measurements of the soil atlocations of unknown density and water content. Using the Soil2For referenced ASTM s
33、tandards, 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 Summary page onthe ASTM website.3The boldface numbers in parentheses refer to a list of references at the end ofthi
34、s standard.D7698 11a2Model linear correlation functions, the procedure then esti-mates the values of soil density and water content based on themeasured electrical properties.5. Significance and Use5.1 The test method is a procedure for estimating in-placevalues of density and water content of soils
35、 and soil-aggregatesbased on electrical measurements.5.2 The test method may be used for quality control andacceptance testing of compacted soil and soil aggregate mix-tures as used in construction and also for research anddevelopment. The minimal disturbance nature of the method-ology allows repeti
36、tive measurements in a single test locationand statistical analysis of the results.45.3 Limitations:5.3.1 This test method provides an overview of the CIMImeasurement procedure using a controlling console connectedto a soil sensor unit which applies 3.0 MHz radio frequency toan in-place soil via met
37、allic probes are driven at a prescribeddistance apart. This test method does not discuss the details ofthe CIMI electronics, computer, or software that utilize on-board algorithms for estimating the soil density and watercontent5.3.2 It is difficult to address an infinite variety of soils inthis sta
38、ndard. This test method does not address the varioustypes of soils on which the CIMI method may or may not beapplicable. However, data presented in X3.1 provides a list ofsoil types that are applicable for the CIMI use.5.3.3 The procedures used to specify how data are collected,recorded, or calculat
39、ed in this standard are regarded as theindustry standard. In addition, they are representative of thesignificant digits that generally should be retained. The proce-dures prescribed in this standard do not consider materialvariation, purpose for obtaining the data, special purposestudies, or any con
40、siderations for the users objectives; it iscommon practice to increase or reduce significant digits ofreported data to be commensurate with these considerations. Itis beyond the scope of this standard to consider significantdigits used in analytical methods for engineering design.6. Interferences6.1
41、 Anomalies in the test material with electrical impedanceproperties significantly different from construction soils andaggregate evaluated during Soil Model development, such asmetal objects or organic material, may affect the accuracy ofthe test method.6.2 The accuracy of the results obtained by th
42、is test methodmay be influenced by poor contact between the soil electricalprobes and the soil being tested. Large air voids, relative to thevolume of material being tested, that may be present betweensoil probes and the surface of the material being tested maycause incorrect density measurements. T
43、he shape of the soilelectrical probe is important to the quality of the electricalmeasurements collected by the CIMI.6.3 When driving the measuring electrical probes, it iscritical to the accuracy of the measurement that they make acomplete and tight contact with the soil over the entire conicalpart
44、 of the probe.6.4 If the volume of soil material being tested as defined inX2.10 has oversize particles or large voids in the electricalfield, this may cause errors in measurements of electricalproperties. Where lack of uniformity in the soil due to layering,aggregate or voids is suspected, the test
45、 site should beexcavated and visually examined to determine if the testmaterial is representative of the in-situ material in general andif an oversize correction is required in accordance with PracticeD4718. Soils must be homogeneous and practically free ofrocks that are in excess of five centimeter
46、s in diameter andconstruction debris for the most accurate results.6.5 Statistical variance may increase for soil material that issignificantly drier or wetter than optimum water content (2.5 %over optimum or 6.0 % below optimum) as determined usingTest Methods D698 or D1557. Statistical variance ma
47、y in-crease for soil material that is compacted to less than 88 % ofthe maximum dry density as determined using Test MethodsD698 or D1557. The CIMI is generally more accurate when theSoil Model range is broader than the range of soil density andwater content being tested in the field.6.6 If temperat
48、ure measurements are not used, an error maybe introduced in the results depending on the value of thedifference between the temperature of the soil used for the SoilModel and the unknown in-place soil being measured. Allelectrical values are equilibrated to 15.55 C. The equilibrationis necessary bec
49、ause the soil temperature affects the electricalsignals that are measured.6.7 This test method applies only to non-frozen soil. Theelectrical properties of soil change considerably as soil tem-perature approaches the freezing point of the entrained water.6.8 The use of electrical probes with different length thanthose used to make the soil mode will introduce an error in theinterpretation of the data and the estimation of the density ofwater content of the tested soils.6.9 The use of a Soil Model that was generated from adifferent soil than that selected for unknown
