ASTM D6527-00(2008)
(Test Method)Standard Test Method for Determining Unsaturated and Saturated Hydraulic Conductivity in Porous Media by Steady-State Centrifugation (Withdrawn 2017)
Standard Test Method for Determining Unsaturated and Saturated Hydraulic Conductivity in Porous Media by Steady-State Centrifugation (Withdrawn 2017)
SIGNIFICANCE AND USE
Recent results have demonstrated that direct measurements of unsaturated transport parameters, for example, hydraulic conductivity, vapor diffusivity, retardation factors, thermal and electrical conductivities, and water potential, on subsurface materials and engineered systems are essential for defensible site characterization needs of performance assessment as well as restoration or disposal strategies. Predictive models require the transport properties of real systems that can be difficult to obtain over reasonable time periods using traditional methods. Using a SSC-UFA greatly decreases the time required to obtain direct measurements of hydraulic conductivity on unsaturated systems and relatively impermeable materials. Traditionally, long times are required to attain steady-state conditions and distributions of water because normal gravity does not provide a large enough driving force relative to the low conductivities that characterize highly unsaturated conditions or highly impermeable saturated systems (Test Method D5084). Pressure techniques sometimes can not be effective for measuring unsaturated transport properties because they do not provide a body force and cannot act on the entire specimen simultaneously unless the specimen is saturated or near-saturated. A body force is a force that acts on every point within the system independently of other forces or properties of the system. High pressures used on saturated systems often induce fracturing or grain rearrangements and cause compaction as a result of high-point stresses that are generated within the specimen. A SSC-UFA does not produce such high-point stresses.
There are specific advantages to using centrifugal force as a fluid driving force. It is a body force similar to gravity and, therefore, acts simultaneously over the entire system and independently of other driving forces, for example, gravity or matric potential. Additionally, in a SSC-UFA the acceleration can dominate any matric potential g...
SCOPE
1.1 This test method covers the determination of the hydraulic conductivity, or the permeability relative to water, of any porous medium in the laboratory, in particular, the hydraulic conductivity for water in subsurface materials, for example, soil, sediment, rock, concrete, and ceramic, either natural or artificial, especially in relatively impermeable materials or materials under highly unsaturated conditions. This test method covers determination of these properties using any form of steady-state centrifugation (SSC) in which fluid can be applied to a specimen with a constant flux or steady flow during centrifugation of the specimen. This test method only measures advective flow on core specimens in the laboratory.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
WITHDRAWN RATIONALE
This test method covers the determination of the hydraulic conductivity, or the permeability relative to water, of any porous medium in the laboratory, in particular, the hydraulic conductivity for water in subsurface materials, for example, soil, sediment, rock, concrete, and ceramic, either natural or artificial, especially in relatively impermeable materials or materials under highly unsaturated conditions. This test method covers determination of these properties using any form of steady-state centrifugation (SSC) in which fluid can be applied to a specimen with a constant flux or steady flow during centrifugation of the specimen. This test method only measures advective flow on core specimens in...
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D6527 − 00 (2008)
Standard Test Method for
Determining Unsaturated and Saturated Hydraulic
Conductivity in Porous Media by Steady-State
Centrifugation
This standard is issued under the fixed designation D6527; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D2216Test Methods for Laboratory Determination ofWater
(Moisture) Content of Soil and Rock by Mass
1.1 This test method covers the determination of the hy-
D3740Practice for Minimum Requirements for Agencies
draulic conductivity, or the permeability relative to water, of
Engaged in Testing and/or Inspection of Soil and Rock as
anyporousmediuminthelaboratory,inparticular,thehydrau-
Used in Engineering Design and Construction
licconductivityforwaterinsubsurfacematerials,forexample,
D4753Guide for Evaluating, Selecting, and Specifying Bal-
soil, sediment, rock, concrete, and ceramic, either natural or
ances and Standard Masses for Use in Soil, Rock, and
artificial, especially in relatively impermeable materials or
Construction Materials Testing
materials under highly unsaturated conditions. This test
D5084Test Methods for Measurement of Hydraulic Con-
method covers determination of these properties using any
ductivity of Saturated Porous Materials Using a Flexible
formofsteady-statecentrifugation(SSC)inwhichfluidcanbe
Wall Permeameter
applied to a specimen with a constant flux or steady flow
D5730Guide for Site Characterization for Environmental
during centrifugation of the specimen. This test method only
Purposes With Emphasis on Soil, Rock, the Vadose Zone
measures advective flow on core specimens in the laboratory.
and Groundwater (Withdrawn 2013)
1.2 The values stated in SI units are to be regarded as
D6026Practice for Using Significant Digits in Geotechnical
standard. No other units of measurement are included in this
Data
standard.
3. Terminology
1.3 This standard may involve hazardous materials,
3.1 Definitions: For common definitions of terms in this
operations, and equipment. This standard does not purport to
guide, such as porosity, permeability, hydraulic conductivity,
address all of the safety concerns, if any, associated with its
water content, and matric potential (matric suction, water
use. It is the responsibility of the user of this standard to
establish appropriate safety and health practices and deter- suction, or water potential), refer to Terminology D653.
mine the applicability of regulatory limitations prior to use.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 hydraulic steady state—the condition in which the
2. Referenced Documents
water flux density remains constant along the conducting
2.1 ASTM Standards:
system. This is diagnosed as the point at which both the mass
D420GuidetoSiteCharacterizationforEngineeringDesign
and volumetric water contents of the material are no longer
and Construction Purposes (Withdrawn 2011)
changing.
D653Terminology Relating to Soil, Rock, and Contained
3.2.2 SSCM or SSC-UFA—Apparatus to achieve steady-
Fluids
state centrifugation. The SSCM (steady-state centrifugation
method) uses a self-contained flow delivery-specimen system
(1). The SSC-UFA (unsaturated flow apparatus) uses an
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
externalpumptodeliverflowtotherotatingspecimen (2).This
Rock and is the direct responsibility of Subcommittee D18.04 on Hydrologic
Properties and Hydraulic Barriers. test method will describe the SSC-UFA application, but other
Current edition approved Sept. 15, 2008. Published November 2008. Originally
applications are possible. Specific parts for the SSC-UFA are
approved in 2000. Last previous edition approved in 2000 as D6527–2000. DOI:
described in Section 6 as an example of a SSC system.
10.1520/D6527-00R08.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3.2.3 steady-state centrifugation—controlled flow of water
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
or other fluid through a specimen while it is rotating in a
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
The last approved version of this historical standard is referenced on Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
www.astm.org. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6527 − 00 (2008)
centrifuge, as distinct from water retention centrifugation able materials. Traditionally, long times are required to attain
methods which measure drainage from a wet specimen by steady-state conditions and distributions of water because
centrifugation with no flow into the specimen. normal gravity does not provide a large enough driving force
relative to the low conductivities that characterize highly
3.2.4 water flux density—the flow rate of water through a
3 2
unsaturated conditions or highly impermeable saturated sys-
cross-sectional area per unit time, for example, 5 cm /cm /s,
tems(TestMethodD5084).Pressuretechniquessometimescan
written as 5 cm/s.
not be effective for measuring unsaturated transport properties
3.3 Symbols:
becausetheydonotprovideabodyforceandcannotactonthe
entire specimen simultaneously unless the specimen is satu-
K = hydraulic conductivity, cm/s
3 2
rated or near-saturated. A body force is a force that acts on
q = water flux density, cm /cm /s or cm/s
every point within the system independently of other forces or
r = distance from axis of rotation, cm
properties of the system. High pressures used on saturated
ρ = dry density, g/cm
systems often induce fracturing or grain rearrangements and
ω = rotation speed, radians/s
cause compaction as a result of high-point stresses that are
generated within the specimen. A SSC-UFA does not produce
4. Summary of Test Method
such high-point stresses.
4.1 Using a SSC-UFA is effective because it allows the
operator to control the independent variables in Darcy’s Law. 5.2 There are specific advantages to using centrifugal force
Darcy’s Law states that the water flux density equals the asafluiddrivingforce.Itisabodyforcesimilartogravityand,
hydraulic conductivity times the fluid driving force (See therefore, acts simultaneously over the entire system and
Section 11). The driving force is fixed by imposing an independently of other driving forces, for example, gravity or
acceleration on the specimen through an adjustable rotation matric potential. Additionally, in a SSC-UFA the acceleration
speed. The water flux density is fixed by setting the flow rate can dominate any matric potential gradients as the Darcy
into the specimen with an appropriate constant-flow pump and drivingforce.Theuseofsteady-statecentrifugationtomeasure
dispersing the flow front evenly over the specimen. Thus, the
steady-state hydraulic conductivities has recently been demon-
specimen reaches the steady-state hydraulic conductivity strated on various porous media (1,2).
which is dictated by that combined water flux density and
5.3 Several issues involving flow in an acceleration field
driving force. The operator can impose whatever hydraulic
have been raised and addressed by previous and current
conductivity is desired within the operational range of rotation
research (1,4).Thesestudieshaveshownthatcompactionfrom
–4 –9 2
speeds and flow rates, from 10 cm/s (0.l darcy; 10 cm )to
acceleration is negligible for subsurface soils at or near their
–11 –8 –16 2
10 cm/s (10 darcy; 10 cm ). Higher conductivities are
field densities. Bulk densities in these specimens have re-
measured using falling head or constant head methods (3).
mained constant (60.1 g/cm ) because the specimens are
These methods are also convenient to saturate the specimen.
already compacted more than the acceleration can affect them.
Following saturation and constant or falling head
Thenotableexceptionisstructuredsoils.Specialarrangements
measurements, the specimen is stepwise desaturated in the
must be made to preserve their densities, for example, the use
SSC-UFAbyincreasingthespeedanddecreasingtheflowrate,
of speeds not exceeding specific equivalent stresses. As an
allowing steady state to be reached at each step. Because a
example, for most SSC-UFAspecimen geometries, the equiva-
relativelylargedrivingforceisused,theSSC-UFAcanachieve
lent pressure in the specimen at a rotation speed of 2500 rpm
hydraulic steady state in a matter of hours for geologic
isabout2bar.Ifthespecimensignificantlycompactsunderthis
materials,evenatverylowwatercontents.Samplesizeisupto
pressure, a lower speed must be used. Usually, only very fine
about 5-cm diameter and 6-cm length cores. This test method
soils at dry bulk densities less than 1.2 g/cm are a problem.
is distinct from water retention centrifugation methods which
Whole rock, grout, ceramics, or other solids are completely
measure simple drainage from a wet specimen by centrifuga-
unaffectedbytheseaccelerations.Precompactionrunsuptothe
tion with no flow into the specimen. Hydraulic steady state
highest speed for that run are performed in the SSC-UFAprior
cannot be achieved without flow into the specimen.
to the run to observe any compaction effects.
5.4 Three-dimensional deviations of the driving force as a
5. Significance and Use
function of position in the specimen are less than a factor of
5.1 Recent results have demonstrated that direct measure-
two. Theoretically, the situation under which unit gradient
ments of unsaturated transport parameters, for example, hy-
conditions are achieved in a SSC-UFA, in which the change in
draulicconductivity,vapordiffusivity,retardationfactors,ther-
the matric potential with radial distance equals zero (dψ/dr =
mal and electrical conductivities, and water potential, on
0), is best at higher water flux densities, higher speeds, or
subsurface materials and engineered systems are essential for
coarser grain-size, or combination thereof. This is observed in
defensible site characterization needs of performance assess-
potential gradient measurements in the normal operational
ment as well as restoration or disposal strategies. Predictive
range where dψ/dr = 0. The worst case occurs at the lowest
modelsrequirethetransportpropertiesofrealsystemsthatcan
water flux densities in the finest-grained materials (1).
be difficult to obtain over reasonable time periods using
traditional methods. Using a SSC-UFA greatly decreases the 5.5 There is no sidewall leakage problem in the SSC-UFA
time required to obtain direct measurements of hydraulic for soils. The centrifugal force maintains a good seal between
conductivity on unsaturated systems and relatively imperme- the specimen and the wall. As the specimen desaturates, the
D6527 − 00 (2008)
increasing matric potential (which still operates in all direc- results. Reliable results depend on many factors; Practice
tions although there is no potential gradient) keeps the water D3740 provides a means of evaluating some of those factors.
within the specimen, and the acceleration (not being a pres-
6. Apparatus
sure) does not force water into any larger pore spaces such as
along a wall. Therefore, capillary phenomena still hold in the
6.1 A SSC-UFA instrument consists of an ultracentrifuge
SSC-UFA, a fact which is especially important for fractured or with a constant, ultralow flow pump that provides water to the
heterogeneous media (2). Cores of solid material such as rock
specimen surface through a rotating seal assembly and micro-
or concrete, are cast in epoxy sleeves as their specimen holder, dispersal system. An example of a rotor and seal assembly is
and this also prevents sidewall leakage. shown in Fig. 1. Fig. 2 shows an actual SSC-UFA apparatus.
This commercially available SSC-UFAcan reach accelerations
5.6 The SSC-UFA can be used in conjunction with other
of up to 20000 g (soils are generally run only up to 1000 g),
methods that require precise fixing of the water content of a
temperatures can be adjusted from –20 to 150°C. Infusion and
porous material. The SSC-UFA is used to achieve the steady-
syringe pumps can provide constant flow rates as low as 0.001
state water content in the specimen and other test methods are
mL/h. Effluent from the specimen is collected in a transparent,
applied to investigate particular problems as a function of
volumetrically calibrated chamber at the bottom of the speci-
water content. This has been successful in determining diffu-
men assembly. Using a strobe light, an observer can check the
sion coefficients, vapor diffusivity, electrical conductivity,
chamber while the specimen is being centrifuged. Two speci-
monitoring the breakthrough of chemical species (retardation
mens are run at the same time in a SSC-UFA with water
factor),porewaterextraction,solidscharacterization,andother
flowingintoeachbymeansoftwofeedlines,thecentralfeedor
physical or chemical properties as functions of the water
inlet path, and the annular feed. Specific parts are defined as
content (2,5).
follows (see Fig. 1):
6.1.1 Specimen Holder—The metal, polysulfone, fiberglass,
5.7 Hydraulic conductivity can be very sensitive to the
orepoxyshellthatcontainsthesoil,rock,cement,oraggregate
solution chemistry, especially when specimens contain
specimen to be tested.
expandable, or swelling, clay minerals. Water should be used
6.1.2 Specimen Cup—The metal canister that contains the
that is appropriate to the situation, for example, groundwater
specimen holder. It has a dispersion cap that disperses flow
from the site from which the specimen was obtained, or
evenly across the top of the specimen. O-ring seals prevent
rainwater if an experiment is being performed to investigate
waterflowaroundthesidesofthespecimenholder.Thebottom
infiltration of precipitation into a disposal site. Appropriate
of the specimen cup has a cone-shaped spacer that holds the
antimicrobial agents should be used to prevent microbial
bottomoftheholderhorizontalandallowseffluenttodrainout
effects within the specimen, for example, clogging, but should
of the specimen cup.
be chosen with consideration of any important chemical issues
6.1.3 Bucket—The metal shell that holds the specimen cup
inthesystem.Astandardsyntheticporewatersolution,similar
and screws into the rotor.
tothesolutionexpectedinthefield,isusefulwhenitisdifficult
6.1.4 Effluent Collection Chamber—The plastic graduated
to obtain field water. Distilled or deionized water is generally
vessel at the end of the specimen cup that collects the effluent
n
...
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