1、Designation: D6527 00 (2008)Standard Test Method forDetermining Unsaturated and Saturated HydraulicConductivity in Porous Media by Steady-StateCentrifugation1This standard is issued under the fixed designation D6527; the number immediately following the designation indicates the year oforiginal adop
2、tion 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 This test method covers the determination of the hy-draulic conductivity
3、, or the permeability relative to water, ofany porous medium in the laboratory, in particular, the hydrau-lic conductivity for water in subsurface materials, for example,soil, sediment, rock, concrete, and ceramic, either natural orartificial, especially in relatively impermeable materials ormateria
4、ls under highly unsaturated conditions. This testmethod covers determination of these properties using anyform of steady-state centrifugation (SSC) in which fluid can beapplied to a specimen with a constant flux or steady flowduring centrifugation of the specimen. This test method onlymeasures advec
5、tive flow on core specimens in the laboratory.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard may involve hazardous materials,operations, and equipment. This standard does not purport toaddress all of the s
6、afety concerns, if any, associated with itsuse. It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D420 Guide to Site Characteriza
7、tion for Engineering Designand Construction Purposes (Withdrawn 2011)3D653 Terminology Relating to Soil, Rock, and ContainedFluidsD2216 Test Methods for Laboratory Determination of Water(Moisture) Content of Soil and Rock by MassD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing
8、and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4753 Guide for Evaluating, Selecting, and Specifying Bal-ances and Standard Masses for Use in Soil, Rock, andConstruction Materials TestingD5084 Test Methods for Measurement of Hydraulic Con-ductivity of Saturated Porou
9、s Materials Using a FlexibleWall PermeameterD5730 Guide for Site Characterization for EnvironmentalPurposes With Emphasis on Soil, Rock, the Vadose Zoneand Groundwater (Withdrawn 2013)3D6026 Practice for Using Significant Digits in GeotechnicalData3. Terminology3.1 Definitions: For common definition
10、s of terms in thisguide, such as porosity, permeability, hydraulic conductivity,water content, and matric potential (matric suction, watersuction, or water potential), refer to Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 hydraulic steady statethe condition in which thew
11、ater flux density remains constant along the conductingsystem. This is diagnosed as the point at which both the massand volumetric water contents of the material are no longerchanging.3.2.2 SSCM or SSC-UFAApparatus to achieve steady-state centrifugation. The SSCM (steady-state centrifugationmethod)
12、uses a self-contained flow delivery-specimen system(1).4The SSC-UFA (unsaturated flow apparatus) uses anexternal pump to deliver flow to the rotating specimen (2). Thistest method will describe the SSC-UFA application, but otherapplications are possible. Specific parts for the SSC-UFA aredescribed i
13、n Section 6 as an example of a SSC system.3.2.3 steady-state centrifugationcontrolled flow of wateror other fluid through a specimen while it is rotating in a1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.04 on Hy
14、drologicProperties and Hydraulic Barriers.Current edition approved Sept. 15, 2008. Published November 2008. Originallyapproved in 2000. Last previous edition approved in 2000 as D6527 2000. DOI:10.1520/D6527-00R08.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM C
15、ustomer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4The boldface numbers in parentheses refer to the list of refer
16、ences at the end ofthis standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesNOTICE: This standard has either been superseded and replaced by a new version or withdrawn.Contact ASTM International (www.astm.org) for the latest infor
17、mation1centrifuge, as distinct from water retention centrifugationmethods which measure drainage from a wet specimen bycentrifugation with no flow into the specimen.3.2.4 water flux densitythe flow rate of water through across-sectional area per unit time, for example, 5 cm3/cm2/s,written as 5 cm/s.
18、3.3 Symbols:K = hydraulic conductivity, cm/sq = water flux density, cm3/cm2/s or cm/sr = distance from axis of rotation, cm = dry density, g/cm3 = rotation speed, radians/s4. Summary of Test Method4.1 Using a SSC-UFA is effective because it allows theoperator to control the independent variables in
19、Darcys Law.Darcys Law states that the water flux density equals thehydraulic conductivity times the fluid driving force (SeeSection 11). The driving force is fixed by imposing anacceleration on the specimen through an adjustable rotationspeed. The water flux density is fixed by setting the flow rate
20、into the specimen with an appropriate constant-flow pump anddispersing the flow front evenly over the specimen. Thus, thespecimen reaches the steady-state hydraulic conductivitywhich is dictated by that combined water flux density anddriving force. The operator can impose whatever hydraulicconductiv
21、ity is desired within the operational range of rotationspeeds and flow rates, from 104cm/s (0.l darcy; 109cm2)to1011cm/s (108darcy; 1016cm2). Higher conductivities aremeasured using falling head or constant head methods (3).These methods are also convenient to saturate the specimen.Following saturat
22、ion and constant or falling headmeasurements, the specimen is stepwise desaturated in theSSC-UFAby increasing the speed and decreasing the flow rate,allowing steady state to be reached at each step. Because arelatively large driving force is used, the SSC-UFAcan achievehydraulic steady state in a ma
23、tter of hours for geologicmaterials, even at very low water contents. Sample size is up toabout 5-cm diameter and 6-cm length cores. This test methodis distinct from water retention centrifugation methods whichmeasure simple drainage from a wet specimen by centrifuga-tion with no flow into the speci
24、men. Hydraulic steady statecannot be achieved without flow into the specimen.5. Significance and Use5.1 Recent results have demonstrated that direct measure-ments of unsaturated transport parameters, for example, hy-draulic conductivity, vapor diffusivity, retardation factors, ther-mal and electrica
25、l conductivities, and water potential, onsubsurface materials and engineered systems are essential fordefensible site characterization needs of performance assess-ment as well as restoration or disposal strategies. Predictivemodels require the transport properties of real systems that canbe difficul
26、t to obtain over reasonable time periods usingtraditional methods. Using a SSC-UFA greatly decreases thetime required to obtain direct measurements of hydraulicconductivity on unsaturated systems and relatively imperme-able materials. Traditionally, long times are required to attainsteady-state cond
27、itions and distributions of water becausenormal gravity does not provide a large enough driving forcerelative to the low conductivities that characterize highlyunsaturated conditions or highly impermeable saturated sys-tems (Test Method D5084). Pressure techniques sometimes cannot be effective for m
28、easuring unsaturated transport propertiesbecause they do not provide a body force and cannot act on theentire specimen simultaneously unless the specimen is satu-rated or near-saturated. A body force is a force that acts onevery point within the system independently of other forces orproperties of t
29、he system. High pressures used on saturatedsystems often induce fracturing or grain rearrangements andcause compaction as a result of high-point stresses that aregenerated within the specimen. A SSC-UFA does not producesuch high-point stresses.5.2 There are specific advantages to using centrifugal f
30、orceas a fluid driving force. It is a body force similar to gravity and,therefore, acts simultaneously over the entire system andindependently of other driving forces, for example, gravity ormatric potential. Additionally, in a SSC-UFA the accelerationcan dominate any matric potential gradients as t
31、he Darcydriving force. The use of steady-state centrifugation to measuresteady-state hydraulic conductivities has recently been demon-strated on various porous media (1,2).5.3 Several issues involving flow in an acceleration fieldhave been raised and addressed by previous and currentresearch (1,4).
32、These studies have shown that compaction fromacceleration is negligible for subsurface soils at or near theirfield densities. Bulk densities in these specimens have re-mained constant (60.1 g/cm3) because the specimens arealready compacted more than the acceleration can affect them.The notable excep
33、tion is structured soils. Special arrangementsmust be made to preserve their densities, for example, the useof speeds not exceeding specific equivalent stresses. As anexample, for most SSC-UFAspecimen geometries, the equiva-lent pressure in the specimen at a rotation speed of 2500 rpmis about 2 bar.
34、 If the specimen significantly compacts under thispressure, a lower speed must be used. Usually, only very finesoils at dry bulk densities less than 1.2 g/cm3are a problem.Whole rock, grout, ceramics, or other solids are completelyunaffected by these accelerations. Precompaction runs up to thehighes
35、t speed for that run are performed in the SSC-UFA priorto the run to observe any compaction effects.5.4 Three-dimensional deviations of the driving force as afunction of position in the specimen are less than a factor oftwo. Theoretically, the situation under which unit gradientconditions are achiev
36、ed in a SSC-UFA, in which the change inthe matric potential with radial distance equals zero (d/dr =0), is best at higher water flux densities, higher speeds, orcoarser grain-size, or combination thereof. This is observed inpotential gradient measurements in the normal operationalrange where d/dr =
37、0. The worst case occurs at the lowestwater flux densities in the finest-grained materials (1).5.5 There is no sidewall leakage problem in the SSC-UFAfor soils. The centrifugal force maintains a good seal betweenthe specimen and the wall. As the specimen desaturates, theD6527 00 (2008)2increasing ma
38、tric potential (which still operates in all direc-tions although there is no potential gradient) keeps the waterwithin the specimen, and the acceleration (not being a pres-sure) does not force water into any larger pore spaces such asalong a wall. Therefore, capillary phenomena still hold in theSSC-
39、UFA, a fact which is especially important for fractured orheterogeneous media (2). Cores of solid material such as rockor concrete, are cast in epoxy sleeves as their specimen holder,and this also prevents sidewall leakage.5.6 The SSC-UFA can be used in conjunction with othermethods that require pre
40、cise fixing of the water content of aporous material. The SSC-UFA is used to achieve the steady-state water content in the specimen and other test methods areapplied to investigate particular problems as a function ofwater content. This has been successful in determining diffu-sion coefficients, vap
41、or diffusivity, electrical conductivity,monitoring the breakthrough of chemical species (retardationfactor), pore water extraction, solids characterization, and otherphysical or chemical properties as functions of the watercontent (2,5).5.7 Hydraulic conductivity can be very sensitive to thesolution
42、 chemistry, especially when specimens containexpandable, or swelling, clay minerals. Water should be usedthat is appropriate to the situation, for example, groundwaterfrom the site from which the specimen was obtained, orrainwater if an experiment is being performed to investigateinfiltration of pre
43、cipitation into a disposal site. Appropriateantimicrobial agents should be used to prevent microbialeffects within the specimen, for example, clogging, but shouldbe chosen with consideration of any important chemical issuesin the system.Astandard synthetic pore water solution, similarto the solution
44、 expected in the field, is useful when it is difficultto obtain field water. Distilled or deionized water is generallynot useful unless the results are to be compared to other testsusing similar water or is specified in pertinent test plans,ASTM test methods, or EPA procedures. Distilled water candr
45、amatically affect the conductivity of soil and rock specimensthat contain clay minerals, and can induce dissolution/precipitation within the specimen.5.8 This test method establishes a dynamic system, and, assuch, the steady-state water content is usually higher than thatwhich is attained during a p
46、ressure plate or other equilibriummethod that does not have flow into the specimen duringoperation. This is critical when using either type of data formodeling purposes. This test method does not measure watervapor transport or molecular diffusion of water, both of whichbecome very significant at lo
47、w conductivities, and may actu-ally dominate when hydraulic conductivities drop much below1010cm/s.5.9 The quality of the result produced by this test methoddepends upon the competence of the personnel performing it,and the suitability of the equipment and facilities used.Agencies that meet the crit
48、eria of Practice D3740 are generallyconsidered capable of competent and objective testing andsampling. Users of this test method are cautioned that compli-ance with Practice D3740 does not in itself ensure reliableresults. Reliable results depend on many factors; PracticeD3740 provides a means of ev
49、aluating some of those factors.6. Apparatus6.1 A SSC-UFA instrument consists of an ultracentrifugewith a constant, ultralow flow pump that provides water to thespecimen surface through a rotating seal assembly and micro-dispersal system. An example of a rotor and seal assembly isshown in Fig. 1. Fig. 2 shows an actual SSC-UFA apparatus.This commercially available SSC-UFAcan reach accelerationsof up to 20 000 g (soils are generally run only up to 1 000 g),temperatures can be adjusted from 20 to 150C. Infusion andsyringe pumps can provide constant flow rate
