ASTM D7664-10(2018)e1
(Test Method)Standard Test Methods for Measurement of Hydraulic Conductivity of Unsaturated Soils
Standard Test Methods for Measurement of Hydraulic Conductivity of Unsaturated Soils
SIGNIFICANCE AND USE
5.1 The hydraulic conductivity function (HCF) is fundamental to hydrological characterization of unsaturated soils and is required for most analyses of water movement in unsaturated soils. For instance, the HCF is a critical parameter to analyze the movement of water during infiltration or evaporation from soil specimens. This is relevant to the evaluation of water movement in landfill cover systems, stiffness changes in pavements due to water movement, recharge of water into aquifers, and extraction of pore water from soils for sampling.
5.2 Examples of HCFs reported in the technical literature are shown in Fig. 1(a), Fig. 1(b), and Fig. 1(c), for clays, silts, and sands, respectively. The decision to report a HCF in terms of suction or volumetric water content depends on the test method and instruments used to measure the HCF. The methods in Categories A and C will provide a HCF in terms of either suction or volumetric water content, while the methods in Category B will provide a HCF in terms of suction.
FIG. 1 Experimental HCFs for Different Soils: (a) k-ψ for Clays; (b) k-θ for Silts; (c) k-θ for Sands (3-14)
5.3 A major assumption involved in measurement of the hydraulic conductivity is that it is used to quantify movement of water in liquid form through unsaturated soils (that is, it is the coefficient of proportionality between liquid water flow and hydraulic gradient). Water can also move through soil in vapor form, but different mechanisms govern impedance of a soil to water vapor flow (diffusion). Accordingly, the HCF is only applicable in engineering practice for degrees of saturation in which the water phase is continuous (that is, no pockets of “unconnected” water). Although this depends on the soil type and texture, this approximately corresponds to degrees of saturation greater than 50 to 60 %.
5.4 The HCFs of soils may be sensitive to the porosity, soil structure, compaction (compaction gravimetric water content and dry unit weight), effe...
SCOPE
1.1 These test methods cover the quantitative measurement of data points suitable for defining the hydraulic conductivity functions (HCF) of unsaturated soils. The HCF is defined as either the relationship between hydraulic conductivity and matric suction or that between hydraulic conductivity and volumetric water content, gravimetric water content, or the degree of saturation. Darcy’s law provides the basis for measurement of points on the HCF, in which the hydraulic conductivity of a soil specimen is equal to the coefficient of proportionality between the flow rate of water through the specimen and the hydraulic gradient across the specimen. To define a point on the HCF, a hydraulic gradient is applied across a soil specimen, the corresponding transient or steady-state water flow rate is measured (or vice versa), and the hydraulic conductivity calculated using Darcy’s law is paired with independent measurements of matric suction or volumetric water content in the soil specimen.
1.2 These test methods describe a family of test methods that can be used to define points on the HCF for different types of soils. Unfortunately, there is no single test that can be applied to all soils to measure the HCF due to testing times and the need for stress control. It is the responsibility of the requestor of a test to select the method that is most suitable for a given soil type. Guidance is provided in the significance and use section of these test methods.
1.3 Similar to the Soil Water Retention Curve (SWRC), defined as the relationship between volumetric water content and matric suction, the HCF may not be a unique function. Both the SWRC and HCF may follow different paths whether the unsaturated soil is being wetted or dried. A test method should be selected which replicates the flow process occurring in the field.
1.4 These test methods describe three categories of methods (Categories A through C) for direct measurement...
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
´1
Designation: D7664 − 10 (Reapproved 2018)
Standard Test Methods for
Measurement of Hydraulic Conductivity of Unsaturated
Soils
This standard is issued under the fixed designation D7664; 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.
ε NOTE—Reapproval with changes editorially added in October 2018.
1. Scope 1.4 Thesetestmethodsdescribethreecategoriesofmethods
(Categories A through C) for direct measurement of the HCF.
1.1 These test methods cover the quantitative measurement
CategoryA(column tests) involves methods used to define the
of data points suitable for defining the hydraulic conductivity
HCF using measured one-dimensional profiles of volumetric
functions (HCF) of unsaturated soils. The HCF is defined as
water content or suction with height in a column of soil
either the relationship between hydraulic conductivity and
compacted into a rigid wall permeameter during imposed
matric suction or that between hydraulic conductivity and
transient and steady-state water flow processes. Different
volumetric water content, gravimetric water content, or the
means of imposing water flow processes are described in
degree of saturation. Darcy’s law provides the basis for
separate methods within Category A. Category B (axis trans-
measurement of points on the HCF, in which the hydraulic
lation tests) involves methods used to define the HCF using
conductivity of a soil specimen is equal to the coefficient of
outflow measurements from a soil specimen underlain by a
proportionality between the flow rate of water through the
saturated high-air entry porous disc in a permeameter during
specimen and the hydraulic gradient across the specimen. To
imposed transient water flow processes. The uses of rigid-wall
define a point on the HCF, a hydraulic gradient is applied
or flexible-wall permeameters are described in separate meth-
across a soil specimen, the corresponding transient or steady-
ods within Category B. Category C (centrifuge permeameter
state water flow rate is measured (or vice versa), and the
test) includes a method to define the HCF using measured
hydraulic conductivity calculated using Darcy’s law is paired
volumetricwatercontentorsuctionprofilesinacolumnofsoil
with independent measurements of matric suction or volumet-
confined in a centrifuge permeameter during imposed steady-
ric water content in the soil specimen.
statewaterflowprocesses.Themethodsinthisstandardcanbe
1.2 These test methods describe a family of test methods
used to measure hydraulic conductivity values ranging from
thatcanbeusedtodefinepointsontheHCFfordifferenttypes
the saturated hydraulic conductivity of the soil to approxi-
of soils. Unfortunately, there is no single test that can be -11
mately 10 m/s.
appliedtoallsoilstomeasuretheHCFduetotestingtimesand
1.5 The methods of data analysis described in these test
the need for stress control. It is the responsibility of the
methods involve measurement of the water flow rate and
requestor of a test to select the method that is most suitable for
hydraulic gradient, and calculation of the hydraulic conductiv-
a given soil type. Guidance is provided in the significance and
ity using Darcy’s law (direct methods) (1). Alternatively,
use section of these test methods.
inversemethodsmayalsobeusedtodefinetheHCF (2).These
1.3 Similar to the Soil Water Retention Curve (SWRC),
employ an iterative, regression-based approach to estimate the
defined as the relationship between volumetric water content
hydraulicconductivitythatasoilspecimenwouldneedtohave
and matric suction, the HCF may not be a unique function.
given a measured water flow response. However, as they
Both the SWRC and HCF may follow different paths whether
require specialized engineering analyses, they are excluded
the unsaturated soil is being wetted or dried. A test method
from the scope of these test methods.
should be selected which replicates the flow process occurring
1.6 These test methods apply to soils that do not change
in the field.
significantly in volume during changes in volumetric water
content or suction, or both (that is, expansive clays or collaps-
ing soils). This implies that these methods should be used for
ThesetestmethodsareunderthejurisdictionofASTMCommitteeD18onSoil
sands, silts, and clays of low plasticity.
and Rock and are the direct responsibility of Subcommittee D18.04 on Hydrologic
Properties and Hydraulic Barriers.
Current edition approved Oct. 1, 2010. Published November 2018. Originally
approved in 2010. Last previous edition approved in 2010 as D635–10. DOI: Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
10.1520/D7664–10R18E01. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D7664 − 10 (2018)
1.7 The methods apply only to soils containing two pore D3740Practice for Minimum Requirements for Agencies
fluids: a gas and a liquid. The liquid is usually water and the Engaged in Testing and/or Inspection of Soil and Rock as
gas is usually air. Other fluids may also be used if requested. Used in Engineering Design and Construction
Caution shall be exercised if the liquid being used causes D4318Test Methods for Liquid Limit, Plastic Limit, and
shrinkage or swelling of the soil. Plasticity Index of Soils
D5084Test Methods for Measurement of Hydraulic Con-
1.8 The units used in reporting shall be SI units in order to
ductivity of Saturated Porous Materials Using a Flexible
be consistent with the literature on water flow analyses in
Wall Permeameter
unsaturated soils. The hydraulic conductivity shall be reported
D5101Test Method for Measuring the Filtration Compat-
in units of [m/s], the matric suction in units of [kPa], the
3 3
ibility of Soil-Geotextile Systems
volumetric water content in [m /m ] or [%], and the degree of
3 3 D6026Practice for Using Significant Digits in Geotechnical
saturation in [m /m ].
Data
1.9 All observed and calculated values shall conform to the
D6527Test Method for Determining Unsaturated and Satu-
guideforsignificantdigitsandroundingestablishedinPractice
rated Hydraulic Conductivity in Porous Media by Steady-
D6026. The procedures in Practice D6026 that are used to 4
State Centrifugation (Withdrawn 2017)
specify how data are collected, recorded, and calculated are
D6836Test Methods for Determination of the Soil Water
regarded as the industry standard. In addition, they are repre-
Characteristic Curve for Desorption Using Hanging
sentative of the significant digits that should generally be
Column, Pressure Extractor, Chilled Mirror Hygrometer,
retained. The procedures do not consider material variation,
or Centrifuge
purpose for obtaining the data, special purpose studies, or any
considerations for the objectives of the user. Increasing or
3. Terminology
reducing the significant digits of reported data to be commen-
3.1 Definitions:
surate with these considerations is common practice. Consid-
3.1.1 Forcommondefinitionsoftermsinthisstandard,refer
eration of the significant digits to be used in analysis methods
to Terminology D653.
for engineering design is beyond the scope of these test
3.2 Definitions of Terms Specific to This Standard:
methods.
-1
3.2.1 airentrysuction,ψ ,(FL ),n—thesuctionrequiredto
a
1.10 This standard does not purport to address all of the
introduceairinto(andthrough)theporesofasaturatedporous
safety concerns, if any, associated with its use. It is the
material (soil or porous plate).
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3.2.2 angular velocity,ω, (radians/T), n—the angular speed
mine the applicability of regulatory limitations prior to use.
of a centrifuge.
1.11 This international standard was developed in accor-
3.2.3 axis translation, n—the principle stating that a matric
dance with internationally recognized principles on standard-
suction ψ can be applied to a soil by controlling the pore air
ization established in the Decision on Principles for the
pressure u and the pore water pressure u so that the
a w
Development of International Standards, Guides and Recom-
difference between the pore air and water pressures equals the
mendations issued by the World Trade Organization Technical
desired matric suction, that is, ψ=u −u .
a w
Barriers to Trade (TBT) Committee.
3.2.4 capacitance probe, n—a tool used to infer the volu-
2. Referenced Documents
metric water content of an unsaturated soil through measure-
ment of the capacitance of a probe embedded within the soil.
2.1 ASTM Standards:
D422Test Method for Particle-SizeAnalysis of Soils(With-
3.2.5 centrifuge permeameter, n—a system having the pur-
drawn 2016)
poses of holding a soil specimen in a centrifuge, applying
D653Terminology Relating to Soil, Rock, and Contained
inflow rates to the top of the soil specimen, and collecting
Fluids
outflow from the bottom of the soil specimen.
D854Test Methods for Specific Gravity of Soil Solids by
3 -3
3.2.6 degree of saturation S , (L L ),n—the ratio of: (1)
r
Water Pycnometer
thevolumeofwaterinagivensoilorrockmass,to (2)thetotal
D1587Practice for Thin-Walled Tube Sampling of Fine-
volume of intergranular space (voids).
Grained Soils for Geotechnical Purposes
3.2.7 flexible-wall permeameter, n—a setup used to control/
D2216TestMethodsforLaboratoryDeterminationofWater
measuretheflowandhydraulicgradientacrossasoilspecimen
(Moisture) Content of Soil and Rock by Mass
contained within a latex membrane.
D2487Practice for Classification of Soils for Engineering
Purposes (Unified Soil Classification System)
3.2.8 g-level, N , (D), n—the ratio of the acceleration of
r,mid
gravity g to the centripetal acceleration, equal to ω (r -z )/g,
0 mid
where r is equal to the radius at the bottom of the centrifuge
3 0
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
permeameter, and z is the distance from the base of the soil
mid
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on specimen to its mid-height.
the ASTM website.
3.2.9 high air-entry porous disc, n—a disc made of metal,
The last approved version of this historical standard is referenced on
www.astm.org. ceramic, or other porous material that can transmit water and
´1
D7664 − 10 (2018)
has an air entry pressure exceeding the highest matric suction capable of lifting the liquid. In tests run using this standard, h
v
to be applied during a test. is negligible compared with the other components.
3 -3
3.2.21 volumetric water content, θ, (L L or %),n—the
3.2.10 high air-entry porous membrane, n—a porous poly-
ratioofthevolumeofwatercontainedintheporespacesofsoil
meric membrane that transmits water and has an air entry
or rock to the total volume of soil or rock.
suction greater than the highest suction to be applied during a
-1
test.
3.2.22 water discharge velocity, v, (LT ),n—rate of dis-
-1
chargeofwaterthroughaporousmediumperunitoftotalarea
3.2.11 hydraulic conductivity, k, (LT ) ,n—the rate of
perpendicular to the direction of flow.
discharge of water under laminar flow conditions through a
unit cross-sectional area of porous medium under a unit
3.2.23 water flow rate, Q, n—the volumetric rate of flow of
hydraulicgradientandstandardtemperatureconditions(20°C).
water through a soil specimen.
The hydraulic conductivity is defined as the coefficient of
proportionality between the water discharge velocity and the
4. Summary of Test Method
spatial gradient in hydraulic head across a saturated or unsatu-
4.1 Method A—Column Tests:
rated soil specimen, as follows:
4.1.1 CategoryAincludesfourmethods(MethodsA1toA4)
v
which involve measurement of changes in volumetric water
k 5 (1)
i
contentandsuctionoverspaceandtimeinasoilspecimenheld
within a horizontally- or vertically-oriented column during
3.2.12 hydraulic conductivity function (HCF),
one-dimensional water flow.
n—relationship between the hydraulic conductivity and the
4.1.2 Method A1 involves downward infiltration of water
matric suction, volumetric water content, or degree of satura-
onto the surface of an initially unsaturated soil specimen,
tion.
MethodA2 involves upward imbibition of water from the base
3.2.13 hydraulic gradient, i, (D), n—the change in total
of an initially unsaturated soil specimen, Method A3 involves
hydraulic head, ∆h, per unit distance Lin the direction of fluid
downward drainage of water from an initially saturated soil
flow, or i = ∆h/L.
specimen, and MethodA4 involves evaporation of water from
-1
3.2.14 infiltration rate, (LT ),n—the value of the water
an initially saturated soil specimen.
discharge velocity applied to the surface of a soil specimen to 4.1.3 MethodsA1toA4canbeusedforawiderangeofsoil
simulate infiltration.
types, but their practical application will depend on the time
-2 required to impose water flow through the soil specimen.
3.2.15 matric suction,ψ, (FL ),n—the difference between
Methods A1 through A4 shall not be used for soils with high
theporegaspressureu andtheporewaterpressureu insoil;
g w
plasticitybecauseofprohibitivetestingtimes,potentialforsoil
thatisψ=u −u ,whichyieldsapositivevalue.Theporegas
g w
cracking, side-wall leakage, and prohibitive column lengths to
in this test method is assumed to be air under pressure u,so
a
avoid outflow boundary effects. Methods A1 and A2 shall be
ψ=u −u .
a w
used for fine-grained sands and for low-plasticity silts. In the
3.2.16 pressure chamber, n—a setup that involves a rigid-
caseofMethodA1,coarse-grainedsoilsmaybesubjecttoflow
wall oedometer cell contained within a pressure vessel. This
throughpreferentialpathways,whileinthecaseofMethodA2,
chamber is used to independently apply a gas pressure to one
coarse-grained soils may not have sufficient capillary rise.
sideandwaterpressuretotheothersideofasoilspecimenheld
Methods A1 and A2 can be used to measure k values
within the oedometer in order to impose an average value of
corresponding to matric suction values ranging from 0 to 80
matric suction on the specimen.
kPa (12 psi) the upper limit on common matric suction
instrumentation). Method A3 shall be used with fine- or
3.2.17 soil-water retention curve (SWRC), n—relationship
coarse-grained sands. MethodA3 shall not be used for silts or
between matric su
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.