ASTM D5126/D5126M-90(2010)e1

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D5126/D5126M − 90(Reapproved 2010)
Standard Guide for
Comparison of Field Methods for Determining Hydraulic
Conductivity in Vadose Zone
This standard is issued under the fixed designation D5126/D5126M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—The units statement in 1.6 and the designation were revised editorially in August 2010.
1. Scope and borehole permeameter tests. Many empirical test methods
are used for calculating hydraulic conductivity from data
1.1 This guide covers a review of the test methods for
obtained with each test method. A general description of each
determining hydraulic conductivity in unsaturated soils and
testmethodandspecialcharacteristicsaffectingapplicabilityis
sediments. Test methods for determining both field-saturated
provided.
and unsaturated hydraulic conductivity are described.
1.5 Field test methods used to determine unsaturated hy-
1.2 Measurement of hydraulic conductivity in the field is
draulic conductivity in the field include direct measurement
used for estimating the rate of water movement through clay
techniques and various estimation methods. Direct measure-
liners to determine if they are a barrier to water flux, for
menttechniquesfordeterminingunsaturatedhydraulicconduc-
characterizing water movement below waste disposal sites to
tivityincludetheinstantaneousprofile(IP)testmethodandthe
predictcontaminantmovement,andtomeasureinfiltrationand
gypsum crust method. Estimation techniques have been devel-
drainage in soils and sediment for a variety of applications.
opedusingboreholepermeameterdataandusingdataobtained
Test methods are needed for measuring hydraulic conductivity
−2 −8
from desorption curves (a curve relating water content to
ranging from 1×10 to1×10 cm/s, for both surface and
matric potential).
subsurface layers, and for both field-saturated and unsaturated
flow.
1.6 The values stated in either SI units or inch-pound units
[presented in brackets] are to be regarded separately as
1.3 For these field test methods a distinction must be made
standard. The values stated in each system may not be exact
between “saturated” (K ) and “field-saturated” (K ) hydraulic
s fs
equivalents;therefore,eachsystemshallbeusedindependently
conductivity. True saturated conditions seldom occur in the
of the other. Combining values from the two systems may
vadose zone except where impermeable layers result in the
result in non-conformance with the standard.
presence of perched water tables. During infiltration events or
1.6.1 The gravitational system of inch-pound units is used
in the event of a leak from a lined pond, a “field-saturated”
when dealing with inch-pound units. In this system, the pound
condition develops. True saturation does not occur due to
(lbf)representsaunitofforce(weight),whiletheunitformass
entrapped air (1). The entrapped air prevents water from
isslugs.Therationalizedslugunitisnotgiven,unlessdynamic
moving in air-filled pores that, in turn, may reduce the
(F = ma) calculations are involved.
hydraulic conductivity measured in the field by as much as a
factor of two compared to conditions when trapped air is not
1.7 This standard does not purport to address all of the
present (2). Field test methods should simulate the “field-
safety concerns, if any, associated with its use. It is the
saturated” condition.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
1.4 Field test methods commonly used to determine field-
bility of regulatory limitations prior to use.
saturated hydraulic conductivity include various double-ring
1.8 This guide offers an organized collection of information
infiltrometertestmethods,air-entrypermeametertestmethods,
or a series of options and does not recommend a specific
course of action. This document cannot replace education or
experienceandshouldbeusedinconjunctionwithprofessional
ThisguideisunderthejurisdictionofASTMCommitteeD18onSoilandRock
judgment. Not all aspects of this guide may be applicable in all
and is the direct responsibility of Subcommittee D18.21 on Groundwater and
circumstances. This ASTM standard is not intended to repre-
Vadose Zone Investigations.
Current edition approved Aug. 1, 2010. Published September 2010. Originally
sent or replace the standard of care by which the adequacy of
approved in 1990. Last previous edition approved in 2004 as D5126–90(2004).
a given professional service must be judged, nor should this
DOI: 10.1520/D5126_D5126M-90R10E01.
document be applied without consideration of a project’s many
The boldface numbers in parentheses refer to a list of references at the end of
the text. unique aspects. The word “Standard” in the title of this
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D5126/D5126M − 90 (2010)
document means only that the document has been approved have been employed to determine the field-saturated hydraulic
through the ASTM consensus process. conductivity of material within the unsaturated zone (4). The
principles of operation of these methods are similar in that the
2. Referenced Documents
steady volumetric flux of water infiltrating into the soil
enclosed within the infiltrometer ring is measured. Saturated
2.1 ASTM Standards:
D653Terminology Relating to Soil, Rock, and Contained hydraulic conductivity is derived directly from solution of
Darcy’s Equation for saturated flow. Primary assumptions are
Fluids
D2434Test Method for Permeability of Granular Soils that the volume of soil being tested is field saturated and that
the saturated hydraulic conductivity is a function of the flow
(Constant Head)
D3385Test Method for Infiltration Rate of Soils in Field rate and the applied hydraulic gradient across the soil volume.
Using Double-Ring Infiltrometer 4.1.1.3 Additional assumptions common to infiltrometer
D4643Test Method for Determination of Water (Moisture)
tests are as follows:
Content of Soil by Microwave Oven Heating (a)The movement of water into the soil profile is one-
dimensional downward.
3. Terminology
(b)Equipment compliance effects are minimal and may be
3.1 Definitions:
disregarded or easily accounted for.
3.1.1 Definitions shall be in accordance with Terminology (c)Thepressureofsoilgasdoesnotofferanyimpedanceto
D653.
the downward movement of the wetting front.
3.2 Definitions of Terms Specific to This Standard: (d)The wetting front is distinct and easily determined.
3.2.1 Descriptions of terms shall be in accordance with Ref
(e)Dispersion of clays in the surface layer of finer soils is
(2). insignificant.
(f)The soil is non-swelling, or the effects of swelling can
4. Summary of Guide
easily be accounted for.
4.1 Test Methods for Measuring Saturated Hydraulic Con-
4.1.2 Single-Ring Infiltrometer:
ductivity Above the Water Table—There are several test meth-
4.1.2.1 The single-ring infiltrometer typically consists of a
ods available for determining the field saturated hydraulic
cylindrical ring 30 cm or larger in diameter that is driven
conductivity of unsaturated materials above the water table.
several centimetres into the soil. Water is ponded within the
Most of these methods involve measurement of the infiltration
ring above the soil surface. The upper surface of the ring is
rateofwaterintothesoilfromaninfiltrometerorpermeameter
often covered to prevent evaporation. The volumetric rate of
device.Infiltrometerstypicallymeasureconductivityatthesoil
water added to the ring sufficient to maintain a constant head
surface, whereas permeameters may be used to determine
within the ring is measured.Alternatively, if the head of water
conductivity at different depths within the soil profile. A
within the ring is relatively large, a falling head type test may
representative list of the most commonly used equipment
be used wherein the flow rate, as measured by the rate of
includes the following: infiltrometers (single and double-ring
decline of the water level within the ring, and the head for the
infiltrometers), double-tube method, air-entry permeameter,
later portion of the test are used in the calculations. Infiltration
and borehole permeameter methods (constant and multiple
is terminated after the flow rate has approximately stabilized.
head methods).
The infiltrometer is removed immediately after termination of
4.1.1 Infiltrometer Test Method:
infiltration, and the depth to the wetting front is determined
4.1.1.1 Infiltrometer test methods measure the rate of infil-
either visually, with a penetrometer-type probe, or by moisture
tration at the soil surface (see Test Method D2434) that is
content determination for soil samples (see Test Method
influenced both by saturated hydraulic conductivity as well as
D4643).
capillary effects of soil (3). Capillary effect refers to the ability
4.1.2.2 A special type of single-ring infiltrometer is the
ofdrysoiltopullorwickwaterawayfromazoneofsaturation
ponded infiltration basin. This type of test is conducted by
faster than would occur if soil were uniformly saturated. The
pondingwaterwithinagenerallyrectangularbasinthatmaybe
magnitude of the capillary effect is determined by initial
as large as several metres on a side. The flow rate required to
moisture content at the time of testing, the pore size, soil
maintainaconstantheadofwaterwithinthepondismeasured.
physical characteristics (texture, structure), and a number of
If the depth of ponding is negligible compared to the depth of
other factors. By waiting until steady-state infiltration is
the wetting front, the steady state flux of water across the soil
reached, the capillary effects are minimized.
surface within the basin is presumed to be equal to the
4.1.1.2 Most infiltrometers generally employ the use of a
saturated hydraulic conductivity of the soil.
metal cylinder placed at shallow depths into the soil, and
4.1.2.3 Anothervariantofthesingle-ringinfiltrometeristhe
include the single-ring infiltrometer, the double-ring
air-entry permeameter (see Fig. 1). The air-entry permeameter
infiltrometer, and the infiltration gradient method. Various
is discussed in 4.1.4.
adaptationstothedesignandimplementationofthesemethods
4.1.3 Double-Ring Infiltrometer:
4.1.3.1 The underlying principles and method of operation
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
of the double-ring infiltrometer are similar to the single-ring
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
infiltrometer, with the exception that an outer ring is included
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. to ensure that one-dimensional downward flow exists within
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D5126/D5126M − 90 (2010)
4.1.4 Double-Tube Test Method:
4.1.4.1 The double-tube test method proposed by Bouwer
(5, 6, 7) has been described by Boersma (8) as a means of
measuringthehorizontal,aswellasthevertical,field-saturated
hydraulic conductivity of material in the vadose zone.
4.1.4.2 This test method as proposed by Bouwer (5, 6, 7)
utilizes two coaxial cylinders positioned in an auger hole. The
differencebetweentherateofflowintheinnercylinderandthe
simultaneousrateofcombinedflowfromintheinnerandouter
cylinders is used to calculate K .
fs
4.1.4.3 Aboreholeisauguredtothedesireddepthandahole
conditioning device is used to square the bottom of the hole.
The hole is then cleaned anda1to 2-cm layer of coarse
protective sand is placed in the bottom of the hole. An outer
tube is then placed in the hole and sunken about 5 cm into the
soil.Theoutertubeisthenfilledwithwaterandasmallerinner
tube is placed at the center of the outer tube. It is then driven
FIG. 1 Diagram of the Equipment for the Air-Entry Permeameter
Technique (from Klute, 1986)
into the soil. A top plate assembly (see Fig. 2) consisting of
water supply valves and standpipes for the inner and outer
cylinders is installed. Water is then supplied to both cylinders.
the tested horizon of the inner ring. Water that infiltrated
Thestandpipefortheoutercylinderisallowedtooverflowand
through the outer ring acts as a barrier to lateral movement of
thestandpipegagefortheinnercylinderissetat0byadjusting
water from the inner ring (see Fig. 2). Double-ring infiltrom-
the appropriate water supply values. After an equilibrium
etersmaybeeitheropentotheatmosphere,ormostcommonly,
period of approximately 1 h, the hole is saturated.
theinnerringmaybecoveredtopreventevaporation.Foropen
double-ring infiltrometers, the flow rate is measured directly 4.1.4.4 Aftersaturationisachieved,theleveloffallofwater
from the rate of decline of the water level within the inner ring in the inner standpipe, H, is recorded at given time intervals, t.
for falling head tests, or from the rate of water input necessary H is recorded at least every 5 cm, for a total of at least 30 cm
to maintain a stable head within the inner ring for the constant (Test 2). During this test, water in the outer standpipe remains
headcase;forsealeddouble-ringinfiltrometers,theflowrateis at a constant head.
measured by weighing a sealed flexible bag that is used as the
4.1.4.5 After the data is recorded, the inner reservoir is
supple reservoir for the inner ring (5).
again filled and the inner standpipe water level is set to 0. The
4.1.3.2 Refer to Test Method D3385 for measuring infiltra-
system is allowed to re-equilibrate for a period of time at least
−2 −5
tion rates in the range of 10 to 10 cm/s. A modified
ten times as long as the time required to collect the first data
double-ring infiltrometer test method for infiltration rates from
set.
−5 −8
10 to 10 cm/s is also being developed.
4.1.4.6 After waiting, Test 2 is performed. The levels in the
outerstandpipeandinnerstandpipearebothbroughtto0.Once
again the drop in the inner standpipe in cm, H, is recorded as
a function of time, t. During the second test, however, water
levels in both tubes drop simultaneously. Both tests are then
performedasecondtimeoruntiltheresultsoftwoconsecutive
runs are consistent.
4.1.5 Air-Entry Permeameter:
4.1.5.1 Theair-entrypermeameterissimilartoasingle-ring
infiltrometerindesignandoperationinthatthevolumetricflux
of water into the soil within a single permeameter ring is used
tocalculatefield-saturatedhydraulicconductivity.Theprimary
differences between the two test methods are that the air-entry
permeameter typically penetrates deeper into the soil profile
and measures the air-entry pressure of the soil. Air-entry
pressure is used as an approximatio
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