ASTM D6539-00

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Designation: D 6539 – 00
Standard Test Method for
Measurement of Pneumatic Permeability of Partially
Saturated Porous Materials by Flowing Air
This standard is issued under the fixed designation D6539; 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 (e) indicates an editorial change since the last revision or reapproval.
TABLE 1 Viscosity of Air, µ, as a Function of Temperature
1. Scope
Temperature, °C Viscosity, Pa·s
1.1 This test method covers laboratory determination of the
−5
12 1.778 3 10
coefficient of permeability for the flow of air (pneumatic
−5
14 1.788 3 10
permeability) through partially saturated porous materials.
−5
16 1.798 3 10
−5
1.2 This test method may be used with undisturbed or
18 1.808 3 10
−5
20 1.818 3 10
compactedcoarsegrainedsoils,silts,orleancohesivesoilsthat
−5
22 1.828 3 10
have a low degree of saturation and that have pneumatic
−5
24 1.837 3 10
−5
permeability between 0.001 square micrometre (1.01 milli-
26 1.847 3 10
−5
28 1.857 3 10
darcy) and 100 square micrometre (101 darcy).
1.3 The values stated in SI units are to be regarded as the
standard, unless other units are specifically given. By tradition
inU.S.practice,thepneumaticpermeabilityofporousmediais
Engaged in theTesting and/or Inspection of Soil and Rock
reported in units of darcy, although the SI unit for pneumatic
as Used in Engineering Design and Construction
permeability is square metre.
D 4220 Practices for Preserving and Transporting Soil
1.4 This standard does not purport to address all of the
Samples
safety concerns, if any, associated with its use. It is the
D4525 Test Method for Permeability of Rocks by Flowing
responsibility of the user of this standard to establish appro-
Air
priate safety and health practices and determine the applica-
D4564 Test Method for Density of Soil in Place by the
bility of regulatory limitations prior to use.
Sleeve Method
D4753 Specification for Evaluating, Selecting, and Speci-
2. Referenced Documents
fying Balances and Scales for Use in Testing Soil, Rock,
2.1 ASTM Standards:
and Related Construction Materials
D653 Terminology Relating to Soil, Rock, and Contained
2 D4767 Test Method for Consolidated-Undrained Triaxial
Fluids
Compression Test on Cohesive Soils
D698 Test Method for Laboratory Compaction Character-
D5084 Test Method for Measurement of Hydraulic Con-
istics of Soil Using Standard Effort (12,400 ft·lbf/ft (605
3 2 ductivity of Saturated Porous Materials Using a Flexible
kN·m/m ))
2 Wall Permeameter
D854 Test Method for Specific Gravity of Soils
D5856 Test Method for Measurement of Hydraulic Con-
D1557 Test Method for Laboratory Compaction Character-
ductivity of Porous Material Using a Rigid-Wall,
istics of Soil Using Modified Effort (56,000 ft-lbf/ft
3 2 Compaction-Mold Permeameter
(2,750 kN-m/m ))
E1 Specification for ASTM Thermometers
D1587 Practice for Thin-Walled Tube Geotechnical Sam-
2 E145 Specification for Gravity-Convection and Forced-
pling of Soils
Ventilation Ovens
D2216 TestMethodforLaboratoryDeterminationofWater
2 2.2 American Petroleum Institute Document:
(Moisture) Content of Soil and Rock by Mass
RP-27 Recommended Practice for Determining Permeabil-
D3550 Practice for Ring-Lined Barrel Sampling of Soils
ity of Porous Media
D3740 Practice for Minimum Requirements for Agencies
1 3
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland Annual Book of ASTM Standards, Vol 04.09.
Rock and is the direct responsibility of Subcommittee D18.04 on Hydrologic Annual Book of ASTM Standards, Vol 14.03.
Properties of Soil and Rocks. Annual Book of ASTM Standards, Vol 14.04.
Current edition approved April 10, 2000. Published June 2000. Available fromAmerican Petroleum Institute, 1220 LSt. NW,Washington, DC
Annual Book of ASTM Standards, Vol 04.08. 20005.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6539–00
3. Terminology direction of compaction, and so forth. It is beyond the scope of
this test method to elaborate these dependencies. Rather, this
3.1 Definitions of Terms Specific to This Standard:
test method is intended to be a measurement technique for
3.1.1 darcy—a porous medium has a permeability of one
determining the pneumatic permeability under a certain set of
darcy when a single-phase fluid of 1-MPa·s (1-cP) viscosity
laboratoryconditions.Itistheresponsibilityoftherequestorto
that completely fills the voids of the medium will flow through
specify which soil parameters must be controlled to ensure a
it under conditions of laminar (viscous) flow at a rate of 1
3 2
valid extension of the test results to field conditions.
cm /s/cm of cross-sectional area under a pressure gradient of
4.5 It is assumed that Darcy’s Law is valid. The validity of
1.013 3 10 Pa (1 atm)/cm. (One darcy = 0.9869 square micro
Darcy’s law may be evaluated by plotting the volumetric flow
metre.)
through the specimen against the differential pressure drop
3.1.2 effective confining stress, (Flexible Wall Method
across the specimen. If the individual test points lie within
only)—the difference between the permeameter cell confining
25%ofastraightlinepassingthroughtheorigin,thenDarcy’s
pressure and the mean specimen pore-air-water pressures.
law may be taken as valid.
3.1.2.1 The effective confining stress is assumed to be
distributed as a radial vector exhibiting a linear gradient along
NOTE 3—Darcy’s law is valid only when saturation does not change
the length of the specimen with a minimum at the inlet and a
over time. Long measurement times associated with the use of bubble
maximum at the outlet. meters and manometers may indirectly be an uncontrolled source of
variability when plotting flow versus pressure drop (see 8.2). The
3.1.2.2 For the purposes of this test method, the effective
recommended use of digital electronic flow and pressure sensors leads to
confining stress is stated as a scalar value and calculated as the
considerably reduced measurement times because the user can quickly
confining gage pressure minus the average of the specimen
determine by inspection when a steady state condition has been reached.
inlet and outlet gage pressures.
At that point only a single reading needs to be taken for a reliable
3.1.3 gage pressure—pressure measured relative to ambient
measurement. A rapid course of measurement will minimize dehydration
atmospheric pressure.
of partially saturated specimens.
3.1.4 pneumatic permeability—the capacity of a porous
NOTE 4—Humidifyingthetestgastominimizespecimendehydrationis
medium to conduct gas in the presence of a gas (air) pressure not recommended because: (1) there is no practical way to either measure
or control the relative humidity of the test gas, either at the inlet or outlet
gradient measured as the ratio of volumetric flow through a
of the specimen; (2) the calibration of the electronic flowmeter is for dry
specimen to the resultant pressure drop across it. Also com-
air only and would become unreliable in the presence of water vapor,
monlyknownaspneumaticconductivityorpermeabilitytoair.
especially in view of the potential for irreversible adsorption of moisture
3.2 For definitions of other terms used in this test method,
on the sensor elements; (3) there is a danger of permanent water
see Terminology D653.
condensationinthestatictransferlinesandotherapparatusdeadvolumes;
and (4) the test apparatus would become more complex and difficult to
use.
4. Significance and Use
4.1 This test method applies to the one-dimensional laminar
4.6 Thistestmethodcoverstheuseoftwodifferenttypesof
(viscous) flow of air in porous materials such as soil.
permeameter cells, flexible wall and rigid wall, and two types
of air flow regulation, mass flow control and pressure control.
NOTE 1—This test method deals with porous materials with both
4.7 A flexible wall permeameter is the preferred means for
gaseous (air) and liquid (pore water) mobile fluids: The liquid phase is
much less compressible, has a higher viscosity, and is much more tightly confining the test specimen in accordance with Test Methods
bound to the solid phase by chemical forces. The assumption of single-
D5084, D4525, and D4767. This test method may be
phase flow may still be presumed to be valid since the test gradient
performed using a rigid wall permeameter and all reference to
ensuring the conditions of laminar flow may be low enough that flow of
effective confining stress and the permeameter cell pressure
the liquid phase is negligible.
system shall be disregarded.
4.2 The degree of saturation of the specimen shall be less
4.8 Forsomespecimens,thepneumaticpermeabilitywillbe
than that which would produce significant internal transport of
strongly dependent on the effective confining stress due to
pore water or alter the continuity of air voids under the applied
porosity reduction. Whenever possible, the requestor should
pneumatic gradients. The maximum permissible degree of
specify the field overburden conditions at which this test
saturation must be evaluated by an experienced analyst. In no
method is to be performed. In some specimens, this stress will
instance shall the specimen be so saturated that pore water
vary significantly with flow in an indeterminate way. All
appears at the exit of the permeameter cell during the test.
specimens should be evaluated for this effect by performing
4.3 Thistestmethodisbasedontheassumptionthattherate
thistestmethodattwoormoredifferentconfiningstressvalues
of mass flow through the specimen is constant with time.
when a flexible wall permeameter is used.
4.9 This test method is intended to support soil remediation
NOTE 2—When a specimen contains volatile materials this assumption
operations such as: soil vapor extraction, air sparging, back-
is violated. The mass of gas flowing out will be greater than that flowing
in, the pneumatic gradient is indeterminate and the test may become filling of soils in utility trenches, and similar engineering
meaningless. Such specimens pose special problems and must be decon-
activities.
taminated before analysis in order to minimize health and safety concerns
4.10 The correlation between results obtained with this test
and to prevent contamination of the test apparatus.
method and in situ field measurements has only been partially
4.4 The pneumatic permeability of porous materials may be established.Thesmalllaboratoryspecimenusedinthismethod
strongly dependent on a variety of physical properties includ- may not be representative of the distributed condition on-site
ing the void ratio, the degree of saturation, percent and due to vadose zone fluctuations, changes in soil stratigraphy,
D6539–00
and so forth. For this reason, laboratory test results should be 5.1.2 Flow Control—The flow rate of air shall be regulated
applied to field situations with caution by qualified personnel. upstream from the specimen by a mass flow controller (flow
control method) or a back pressure regulator (pressure control
NOTE 5—This test method is dependent on the competence of the
method), or both. The flow control shall be capable of
personnel performing it and the suitability of the equipment and facilities
regulating air flow between 0.01 and 1000 cm /min to 65%.
used.Agencies which meet the criterion of Practice D3740 are generally
considered capable of competent and objective testing. Two test methods of flow control are required to adapt to a
wide range of specimen permeability:
5. Apparatus
5.1.2.1 Test Method A, Flow Control Mode—This test
method is preferred for high-permeability specimens (greater
5.1 Pneumatic Permeameter—The pneumatic permeameter
than about 0.1 darcy) that require flows in the range from 2 to
shall be capable of rapidly establishing a constant flow of air
1000cm /minandlowspecimeninletpressures.Themassflow
through the test specimen and measuring the consequent
controller is set for the desired flow through the specimen. It
pressure drop across it. A schematic diagram is shown in Fig.
shallautomaticallyadjustitsdownstreampressureasneededto
1.
maintain constant mass flow rate of air regardless of tempera-
5.1.1 Air Supply—Thecompressedairsuppliedtothepneu-
ture or pressure.
matic system shall:
5.1.2.2 Test Method B, Pressure Control Mode—This test
5.1.1.1 Be pulsation-free, have sufficient volumetric capac-
method is preferred for low-permeability specimens (less than
ity at all anticipated flow rates, be free of water vapor to a dew
about 0.1 darcy) that require control of pressure between 5 and
point of −70°C (−94°F) or less, and be free of oil,
35 kPa (1 and 5 psi) at low flow rates: The back pressure
5.1.1.2 Be free of particulate matter greater than 5 µm in
regulatorshallactasavariablepressurereliefvalvethatcanbe
diameter, and
adjusted to produce a fixed inlet pressure. The mass flow
5.1.1.3 Beprovidedwithamonitoringgageandregulatorto
controller is set to produce an airflow slightly in excess of the
deliver a pressure of at least 350 6 5 kPa (50 6 1 psi).
test maximum.
NOTE 6—Other gases than air may be used when specified by the
requestor. It is important that the electronic flowmeter is calibrated for the NOTE 7—The back pressure regulator diverts to the atmosphere a
test gas. Nitrogen is often preferred as having more uniform viscosity and portion of the flow to maintain a constant inlet pressure to produce the
low water content. required specimen flow rate.
FIG. 1 Pneumatic Permeameter
D6539–00
shall be connected to the pressure measuring device port, the normally
5.2 Flow Measurement:
openportshallbeconnectedtothespecimenoutletport,andthenormally
5.2.1 The rate of air flowing into the specimen, Q, shall be
closed port vented to atmosphere. When in the normally open position
measured to a precision better than 3%. The preferred device
(PositionA, Fig. 1), the device measures the specimen pressure drop, DP;
is a digital electronic mass flowmeter upstream from the
when in the normally closed position (Position-B), the device measures
specimen. If such a flowmeter is not available, a bubble meter
the specimen inlet gage pressure, P .
I
at the outlet of the permeameter may be used.
5.3.3 Back Pressure Gage—This gage shall monitor the
NOTE 8—When repetitious, rapid measurements are required, the digi-
pressure down stream from the mass flow controller and
tal electronic mass flowmeters will prove more convenient to use than a
upstream from the specimen inlet with a precision of 61 kPa
bubble meter, especially at high flow rates. The need for careful hand-eye
...