ASTM D7664-2010 2500 Standard Test Methods for Measurement of Hydraulic Conductivity of Unsaturated Soils《测量不饱和土壤的导水率的标准试验方法》.pdf

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1、Designation: D7664 10Standard 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 rev

2、ision. 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 These test methods cover the quantitative measurementof data points suitable for defining the hydraulic conductivityfunctions

3、(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

4、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 c

5、orresponding 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 me

6、thodsthat 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 i

7、s 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

8、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.Categ

9、ory 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 w

10、ater 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 p

11、rocesses. 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 perme

12、ameter 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 me

13、asurement 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 conductivit

14、y 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

15、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.1.7 The methods apply only to soils containing two porefluids: a gas and a liquid. The liquid is usually water and thegas is u

16、sually air. Other fluids may also be used if requested.Caution shall be exercised if the liquid being used causesshrinkage or swelling of the soil.1.8 The units used in reporting shall be SI units in order tobe consistent with the literature on water flow analyses in1These test methods are under the

17、 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 2010. DOI:10.1520/D766410.2The boldface numbers in parentheses refer to the list of ref

18、erences at the end ofthis standard.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.unsaturated soils. The hydraulic conductivity shall be reportedin units of m/s, the matric suction in units of kPa, thevolumetric water content in m3/

19、m3 or %, and the degree ofsaturation in m3/m3.1.9 All observed and calculated values shall conform to theguide for significant digits and rounding established in PracticeD6026. The procedures in Practice D6026 that are used tospecify how data are collected, recorded, and calculated areregarded as th

20、e industry standard. In addition, they are repre-sentative of the significant digits that should generally beretained. The procedures do not consider material variation,purpose for obtaining the data, special purpose studies, or anyconsiderations for the objectives of the user. Increasing orreducing

21、 the significant digits of reported data to be commen-surate with these considerations is common practice. Consid-eration of the significant digits to be used in analysis methodsfor engineering design is beyond the scope of these testmethods.1.10 This standard does not purport to address all of thes

22、afety 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:3D422 Test Method for Particle

23、-Size Analysis of SoilsD653 Terminology Relating to Soil, Rock, and ContainedFluidsD854 Test Methods for Specific Gravity of Soil Solids byWater PycnometerD1587 Practice for Thin-Walled Tube Sampling of Soils forGeotechnical PurposesD2216 Test Methods for Laboratory Determination of Wa-ter (Moisture

24、) Content of Soil and Rock by MassD2487 Practice for Classification of Soils for EngineeringPurposes (Unified Soil Classification System)D3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4318 Test M

25、ethods for Liquid Limit, Plastic Limit, andPlasticity Index of SoilsD5084 Test Methods for Measurement of Hydraulic Con-ductivity of Saturated Porous Materials Using a FlexibleWall PermeameterD5101 Test Method for Measuring the Soil-Geotextile Sys-tem Clogging Potential by the Gradient RatioD6026 Pr

26、actice for Using Significant Digits in GeotechnicalDataD6527 Test Method for Determining Unsaturated and Satu-rated Hydraulic Conductivity in Porous Media by Steady-State CentrifugationD6836 Test Methods for Determination of the Soil WaterCharacteristic Curve for Desorption Using Hanging Col-umn, Pr

27、essure Extractor, Chilled Mirror Hygrometer, orCentrifuge3. Terminology3.1 Definitions:3.1.1 For common definitions of terms in this standard, referto Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 air entry suction, ca, (FL-1), nthe suction required tointroduce air into (

28、and through) the pores of a saturated porousmaterial (soil or porous plate).3.2.2 angular velocity, v, (radians/T), nthe angular speedof a centrifuge.3.2.3 axis translation, nthe principle stating that a matricsuction c can be applied to a soil by controlling the pore airpressure uaand the pore wate

29、r pressure uwso that thedifference between the pore air and water pressures equals thedesired matric suction, that is, c =uauw.3.2.4 capacitance probe, na tool used to infer the volu-metric water content of an unsaturated soil through measure-ment of the capacitance of a probe embedded within the so

30、il.3.2.5 centrifuge permeameter, na system having the pur-poses of holding a soil specimen in a centrifuge, applyinginflow rates to the top of the soil specimen, and collectingoutflow from the bottom of the soil specimen.3.2.6 degree of saturation Sr,(L3L-3), nthe ratio of: (1) thevolume of water in

31、 a given soil or rock mass, to (2) the totalvolume of intergranular space (voids).3.2.7 flexible-wall permeameter, na setup used to control/measure the flow and hydraulic gradient across a soil specimencontained within a latex membrane.3.2.8 g-level, Nr,mid, (D), nthe ratio of the acceleration ofgra

32、vity g to the centripetal acceleration, equal to v2(r0-zmid)/g,where r0is equal to the radius at the bottom of the centrifugepermeameter, and zmidis the distance from the base of the soilspecimen to its mid-height.3.2.9 high air-entry porous disc, na disc made of metal,ceramic, or other porous mater

33、ial that can transmit water andhas an air entry pressure exceeding the highest matric suctionto be applied during a test.3.2.10 high air-entry porous membrane, na porous poly-meric membrane that transmits water and has an air entrysuction greater than the highest suction to be applied during atest.3

34、.2.11 hydraulic conductivity, k, (LT-1), nthe rate ofdischarge of water under laminar flow conditions through aunit cross-sectional area of porous medium under a unithydraulic gradient and standard temperature conditions (20C).The hydraulic conductivity is defined as the coefficient ofproportionalit

35、y between the water discharge velocity and thespatial gradient in hydraulic head across a saturated or unsat-urated soil specimen, as follows:k 5vi(1)3.2.12 hydraulic conductivity function (HCF),nrelationship between the hydraulic conductivity and thematric suction, volumetric water content, or degr

36、ee of satura-tion.3For 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.D7664 1023.2.13 hydraulic gradient, i, (D),

37、 nthe change in totalhydraulic head, Dh, per unit distance L in the direction of fluidflow, or i = Dh/L.3.2.14 infiltration rate, (LT-1), nthe value of the waterdischarge velocity applied to the surface of a soil specimen tosimulate infiltration.3.2.15 matric suction, c, (FL-2), nthe difference betw

38、eenthe pore gas pressure ugand the pore water pressure uwin soil;that is c =uguw, which yields a positive value. The pore gasin this test method is assumed to be air under pressure ua,soc =uauw.3.2.16 pressure chamber, na setup that involves a rigid-wall oedometer cell contained within a pressure ve

39、ssel. Thischamber is used to independently apply a gas pressure to oneside and water pressure to the other side of a soil specimen heldwithin the oedometer in order to impose an average value ofmatric suction on the specimen.3.2.17 soil-water retention curve (SWRC), nrelationshipbetween matric sucti

40、on and volumetric water content.3.2.18 tensiometer, na tool used to measure the matricsuction in soil by measuring the negative water pressure in awater reservoir in equilibrium with a soil via a saturated porousdisc.3.2.19 time domain reflectometer (TDR), na tool used toinfer the volumetric water c

41、ontent of an unsaturated soilthrough measurement of the travel time of an electromagneticpulse through a metallic, shielded rod embedded within thesoil.3.2.20 total hydraulic head, h, nthe sum of three compo-nents at a point: (1) elevation head, he, which is equal to theelevation of the point above

42、a datum; (2) pressure head, hp,which is the height of a column of static water that can besupported by the static pressure at the point; and (3) velocityhead, hv, which is the height the kinetic energy of the liquid iscapable of lifting the liquid. In tests run using this standard, hvis negligible c

43、ompared with the other components.3.2.21 volumetric water content, u, (L3L-3or %), ntheratio of the volume of water contained in the pore spaces of soilor rock to the total volume of soil or rock.3.2.22 water discharge velocity, v, (LT-1), nrate of dis-charge of water through a porous medium per uni

44、t of total areaperpendicular to the direction of flow.3.2.23 water flow rate, Q, nthe volumetric rate of flow ofwater through a soil specimen.4. Summary of Test Method4.1 Method AColumn Tests:4.1.1 CategoryAincludes four methods (MethodsA1 toA4)which involve measurement of changes in volumetric wate

45、rcontent and suction over space and time in a soil specimen heldwithin a horizontally- or vertically-oriented column duringone-dimensional water flow.4.1.2 Method A1 involves downward infiltration of wateronto the surface of an initially unsaturated soil specimen,MethodA2 involves upward imbibition

46、of water from the baseof an initially unsaturated soil specimen, Method A3 involvesdownward drainage of water from an initially saturated soilspecimen, and Method A4 involves evaporation of water froman initially saturated soil specimen.4.1.3 MethodsA1 toA4 can be used for a wide range of soiltypes,

47、 but their practical application will depend on the timerequired to impose water flow through the soil specimen.Methods A1 through A4 shall not be used for soils with highplasticity because of prohibitive testing times, potential for soilcracking, side-wall leakage, and prohibitive column lengths to

48、avoid outflow boundary effects. Methods A1 and A2 shall beused for fine-grained sands and for low-plasticity silts. In thecase of MethodA1, coarse-grained soils may be subject to flowthrough preferential pathways, while in the case of MethodA2,coarse-grained soils may not have sufficient capillary r

49、ise.Methods A1 and A2 can be used to measure k valuescorresponding to matric suction values ranging from 0 to 80kPa (12 psi) the upper limit on common matric suctioninstrumentation). Method A3 shall be used with fine- orcoarse-grained sands. Method A3 shall not be used for silts orclays because of difficulties in saturating the soil specimen andthe long time required for gravity drainage to occur. MethodA3 can be used to measure k values corresponding to matricsuction values from 0 to 200 kPa (29 psi). Method A4 shall beused for any soil with