ASTM_D_6565_-_00_2005.pdf

Designation:D 6565 00(Reapproved 2005)Standard Test Method forDetermination of Water(Moisture)Content of Soil by theTime-Domain Reflectometry(TDR)Method1This standard is issued under the fixed designation D 6565;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(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of watercontent(or moisture content)in soil by the use of theelectromagnetic technique called Time-Domain Reflectometry(TDR).1.2 This test method was written to detail the procedure forconventional TDR measurements of soil.Other TDR applica-tions exist for the purpose of quantifying water content in soiland are not covered here,such as flat probe technologies andwetting front advance methods.1.3 Commercial TDR applications exist which automate theTDR methodology and are not detailed in this test method.It islikely that overlap exists in the automated commercial systemsversus this applied method,and the user is encouraged toadhere to this test method when applicable.1.4 This test method is one of a series on vadose zonecharacterization methods.Other standards have been preparedon vadose zone characterization techniques.1.5 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:2D 653 Terminology Relating to Soil,Rock,and ContainedFluidsD 1452 Practice for Soil Investigations and Sampling byAuger BoringsD 2216 Test Method for Laboratory Determination of Water(Moisture)Content of Soil and Rock by MassD 4643 Test Method for Determination of Water(Moisture)Content of Soil by the Microwave Oven MethodD 4700 Guide for Soil Sampling from the Vadose ZoneD 4944 Test Method for Field Determination of Water(Moisture)Content of Soil by the Calcium Carbide GasPressure Tester MethodD 5220 Test Method for Water Content of Soil and RockIn-Place by the Neutron Depth Probe Method3.Terminology3.1 Definitions:3.1.1 time domain reflectometry(TDR)an electromagneticmethod used in the determination of water content of soil.3.1.2 Definitions of other terminology used in this guidemay be found in Terminology D 653.4.Summary of Test Method4.1 Aspecially constructed,multi-wave-guide TDR probe isinserted into the soil.The electronic cable tester(or automatedcommercial TDR electronics)is used to send a pulsed wave-form to the probe.The cable tester then receives a return signalwhich was influenced by the dielectric constant of the soil,which in turn is a function of water content.An analysis of thewaveform trace supplies the necessary information to calculatethe water content of the soil.5.Significance and Use5.1 The determination of the water-content,or moisturecontent,of soil is one of the fundamental needs in the soilphysics and hydrology disciplines.The need arises fromrequirements for defining the optimal time for irrigation,theinfiltration rate,the soil-moisture flux,contaminant transportrates,and evaluating the potential for leakage from a waste siteor a surface or subsurface barrier.5.2 The TDR application covered in this test method is thatused for point measurements of moisture content in soil.Theapplication is either through manual insertion into the soil or byburying a probe in the subsurface to acquire moisture content1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.21.02 on Vadose ZoneMonitoring.Current edition approved Nov.1,2005.Published December 2005.Originallyapproved in 2000.Last previous edition approved in 2000 as D 6565 00.2For referenced ASTM standards,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.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.data at a specific location.In addition,core samples may betested with TDR at a drill site to acquire real-time soil moisturedata.6.Interferences6.1 TDR measurements in conductive soils are hampered bythe conductivity of the soil and the resulting signal attenuation.Typically,the amplitude of the voltage pulse reflected back tothe TDR instrument is diminished in proportion to the soilselectrical conductivity.When the soils electrical conductivityis high enough,there is insufficient signal strength for the TDRinstrument to detect.TDR probes employing a balancing baluntransformer are particularly susceptible to this effect.The baluntransformer compounds the problems in a