ASTM_D_7698_-_11a.pdf

Designation:D769811aStandard 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 adoption 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,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.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 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 and 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 in 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values shall conform tothe guidelines for significant digits and rounding established inPractice D6026 unless superseded by this standard.1.2 Generalized Theory1.2.1 Two key electrical properties of soil are conductivityand relative dielectric permittivity which are manifested as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 relativedielectric 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 alternating 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,an 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 measured,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 detailed 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 Communications 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 previous edition approved in 2011 as D769811.DOI:10.1520/D7698-11a.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 1.3.2 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 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 Laboratory 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 Character-istics of Soil Using M