1、Designation:D 6565 00Standard 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
2、 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
3、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 technolog
4、ies 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
5、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 o
6、f 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:D 653 Terminology Relating to Soil,Rock,and ContainedFluids2D 1452 Practice for Soil Investigations and S
7、ampling byAuger Boring2D 2216 Test Method for Laboratory Determination of Water(Moisture)Content of Soil and Rock by Mass2D 4643 Test Method for Determination of Water(Moisture)Content of Soil by the Microwave Oven Method2D 4700 Guide for Soil Sampling from the Vadose Zone2D 4944 Test Method for Fie
8、ld Determination of Water(Moisture)Content of Soil by the Calcium Carbide GasPressure Tester Method2D 5220 Test Method for Water Content of Soil and RockIn-Place by the Neutron Depth Probe Method23.Terminology3.1 Definitions:3.1.1 time domain reflectometry(TDR)an electromagneticmethod used in the de
9、termination 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
10、 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 th
11、e 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,co
12、ntaminant 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
13、byburying a probe in the subsurface to acquire moisture contentdata 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
14、 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.TD
15、R probes employing a balancing baluntransformer are particularly susceptible to this effect.The balun1This 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 June 10,2
16、000.Published September 2000.2Annual Book of ASTM Standards,Vol 04.08.1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.transformer compounds the problems in analyzing the signalsfrom probes with rod lengths of 15 cm or less(1).36.2 Clay soils also attenuate a TDR probe signal.Conduc-tive soils which have a significant amount of clay attenuate thesignal the most.Apartial solution to signal loss is to reduce thelength of the probe(2).However,as the probe length s
