ASTM_D_7664_-_10_2018e1.pdf

Designation:D766410(Reapproved 2018)1Standard Test Methods forMeasurement of Hydraulic Conductivity of UnsaturatedSoils1This standard is issued under the fixed designation D7664;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.1NOTEReapproval with changes editorially added in October 2018.1.Scope1.1 These test methods cover the quantitative measurementof data points suitable for defining the hydraulic conductivityfunctions(HCF)of unsaturated soils.The HCF is defined aseither the relationship between hydraulic conductivity andmatric suction or that between hydraulic conductivity andvolumetric water content,gravimetric water content,or thedegree of saturation.Darcys law provides the basis formeasurement of points on the HCF,in which the hydraulicconductivity of a soil specimen is equal to the coefficient ofproportionality between the flow rate of water through thespecimen and the hydraulic gradient across the specimen.Todefine a point on the HCF,a hydraulic gradient is appliedacross a soil specimen,the corresponding transient or steady-state water flow rate is measured(or vice versa),and thehydraulic conductivity calculated using Darcys law is pairedwith independent measurements of matric suction or volumet-ric water content in the soil specimen.1.2 These test methods describe a family of test methodsthat can be used to define points on the HCF for different typesof soils.Unfortunately,there is no single test that can beapplied to all soils to measure the HCF due to testing times andthe need for stress control.It is the responsibility of therequestor of a test to select the method that is most suitable fora given soil type.Guidance is provided in the significance anduse section of these test methods.1.3 Similar to the Soil Water Retention Curve(SWRC),defined as the relationship between volumetric water contentand matric suction,the HCF may not be a unique function.Both the SWRC and HCF may follow different paths whetherthe unsaturated soil is being wetted or dried.A test methodshould be selected which replicates the flow process occurringin the field.1.4 These test methods describe three categories of methods(Categories A through C)for direct measurement of the HCF.Category A(column tests)involves methods used to define theHCF using measured one-dimensional profiles of volumetricwater content or suction with height in a column of soilcompacted into a rigid wall permeameter during imposedtransient and steady-state water flow processes.Differentmeans of imposing water flow processes are described inseparate methods within Category A.Category B(axis trans-lation tests)involves methods used to define the HCF usingoutflow measurements from a soil specimen underlain by asaturated high-air entry porous disc in a permeameter duringimposed transient water flow processes.The uses of rigid-wallor flexible-wall permeameters are described in separate meth-ods within Category B.Category C(centrifuge permeametertest)includes a method to define the HCF using measuredvolumetric water content or suction profiles in a column of soilconfined in a centrifuge permeameter during imposed steady-state water flow processes.The methods in this standard can beused to measure hydraulic conductivity values ranging fromthe saturated hydraulic conductivity of the soil to approxi-mately 10-11m/s.1.5 The methods of data analysis described in these testmethods involve measurement of the water flow rate andhydraulic gradient,and calculation of the hydraulic conductiv-ity using Darcys law(direct methods)(1).2Alternatively,inverse methods may also be used to define the HCF(2).Theseemploy an iterative,regression-based approach to estimate thehydraulic conductivity that a soil specimen would need to havegiven a measured water flow response.However,as theyrequire specialized engineering analyses,they are excludedfrom the scope of these test methods.1.6 These test methods apply to soils that do not changesignificantly in volume during changes in volumetric watercontent or suction,or both(that is,expansive clays or collaps-ing soils).This implies that these methods should be used forsands,silts,and clays of low plasticity.1These test methods are under the jurisdiction ofASTM Committee D18 on Soiland Rock and are the direct responsibility of Subcommittee D18.04 on HydrologicProperties and Hydraulic Barriers.Current edition approved Oct.1,2010.Published November 2018.Originallyapproved in 2010.Last previous edition approved in 2010 as D635 10.DOI:10.1520/D766410R18E01.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in a