ASTM D5126/D5126M-16
(Guide)Standard Guide for Comparison of Field Methods for Determining Hydraulic Conductivity in Vadose Zone
Standard Guide for Comparison of Field Methods for Determining Hydraulic Conductivity in Vadose Zone
SIGNIFICANCE AND USE
5.1 Saturated hydraulic conductivity measurements are made for a variety of purposes varying from design of landfills and construction of clay liners to assessment of irrigation systems. Infiltrometers are commonly used where infiltration or percolation rates through a surface or subsurface layer are desired. Evaluation of the rate of water movement through a pond liner is one example of this kind of measurement. Penetration of the liner by a borehole would invalidate the measurement of liner permeability. It has been noted that small-ring infiltrometers are subject to error due to lateral divergence of flow. Therefore, techniques using very large (1 to 2-m diameter) infiltration basins have been recommended for measuring the very slow percolation rates typically needed for clay liners. The air-entry permeameter can be used instead of infiltrometer tests to avoid lateral divergence of flow. However, because a cylinder must be driven into the media tested, the actual soil column tested may be disrupted by introduction of the cylinder, especially in structured soils.
5.2 Borehole tests for determining saturated hydraulic conductivity are applicable for evaluating the rate of water movement through subsurface layers. For slowly permeable layers, an accurate method of measuring the rate of water movement into the borehole will need to be developed. Use of a flexible bag as a reservoir that can be periodically weighed is advisable for these conditions. A number of mathematical solutions for borehole outflow data are available (Stephens et al. (17), Reynolds et al. (18), and Philip (19)).
5.3 Information on unsaturated flow rates is needed to design hazardous waste landfills and impoundments where prevention of flow of contaminants into groundwater is needed. Of the test methods available, the primary differences are cost and resultant bias and precision. The instantaneous profile test method appears to provide very reliable data because it uses a large volume of so...
SCOPE
1.1 This guide covers a review of the test methods for determining hydraulic conductivity in unsaturated soils and sediments. Test methods for determining both field-saturated and unsaturated hydraulic conductivity are described.
1.2 Measurement of hydraulic conductivity in the field is used for estimating the rate of water movement through clay liners to determine if they are a barrier to water flux, for characterizing water movement below waste disposal sites to predict contaminant movement, and to measure infiltration and drainage in soils and sediment for a variety of applications. Test methods are needed for measuring hydraulic conductivity ranging from 1 × 10−2 to 1 × 10−8 cm/s, for both surface and subsurface layers, and for both field-saturated and unsaturated flow.
1.3 For these field test methods a distinction is made between “saturated” (Ks) and “field-saturated” (Kfs) hydraulic conductivity. True saturated conditions seldom occur in the vadose zone except where impermeable layers result in the presence of perched water tables. During infiltration events or in the event of a leak from a lined pond, a “field-saturated” condition develops. True saturation does not occur due to entrapped air (1).2 The entrapped air prevents water from moving in air-filled pores that, in turn, may reduce the hydraulic conductivity measured in the field by as much as a factor of two compared to conditions when trapped air is not present (2). Field test methods should simulate the “field-saturated” condition.
1.4 Field test methods commonly used to determine field-saturated hydraulic conductivity include various double-ring infiltrometer test methods, air-entry permeameter test methods, and borehole permeameter tests. Many empirical test methods are used for calculating hydraulic conductivity from data obtained with each test method. A general description of each test method and special characteristics affecting applicabili...
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Designation: D5126/D5126M − 16
StandardGuide for
Comparison of Field Methods for Determining Hydraulic
1
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.
1. Scope* obtained with each test method.Ageneral description of each
testmethodandspecialcharacteristicsaffectingapplicabilityis
1.1 This guide covers a review of the test methods for
provided.
determining hydraulic conductivity in unsaturated soils and
sediments. Test methods for determining both field-saturated
1.5 Field test methods used to determine unsaturated hy-
and unsaturated hydraulic conductivity are described.
draulic conductivity in the field include direct measurement
techniques and various estimation methods. Direct measure-
1.2 Measurement of hydraulic conductivity in the field is
menttechniquesfordeterminingunsaturatedhydraulicconduc-
used for estimating the rate of water movement through clay
liners to determine if they are a barrier to water flux, for tivityincludetheinstantaneousprofile(IP)testmethodandthe
gypsum crust method. Estimation techniques have been devel-
characterizing water movement below waste disposal sites to
predictcontaminantmovement,andtomeasureinfiltrationand opedusingboreholepermeameterdataandusingdataobtained
drainage in soils and sediment for a variety of applications. from desorption curves (a curve relating water content to
Test methods are needed for measuring hydraulic conductivity matric potential).
−2 −8
ranging from 1×10 to1×10 cm/s, for both surface and
1.6 The values stated in SI units are to be regarded as
subsurface layers, and for both field-saturated and unsaturated
standard. No other units of measurement are included in this
flow.
standard.
1.3 For these field test methods a distinction is made
1.7 All observed and calculated values shall conform to the
between “saturated” (K ) and “field-saturated” (K ) hydraulic
s fs
guidelines for significant digits and rounding established in
conductivity. True saturated conditions seldom occur in the
Practice D6026.
vadose zone except where impermeable layers result in the
presence of perched water tables. During infiltration events or 1.7.1 The method used to specify how data are collected,
in the event of a leak from a lined pond, a “field-saturated”
calculated,orrecordedinthisstandardisnotdirectlyrelatedto
condition develops. True saturation does not occur due to theaccuracytowhichthedatacanbeappliedindesignorother
2
entrapped air (1). The entrapped air prevents water from
uses, or both. How one applies the results obtained using this
moving in air-filled pores that, in turn, may reduce the
standard is beyond its scope.
hydraulic conductivity measured in the field by as much as a
1.8 This standard does not purport to address all of the
factor of two compared to conditions when trapped air is not
safety concerns, if any, associated with its use. It is the
present (2). Field test methods should simulate the “field-
responsibility of the user of this standard to establish appro-
saturated” condition.
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
1.9 This guide offers an organized collection of information
infiltrometertestmethods,air-entrypermeametertestmethods,
or a series of options and does not recommend a specific
and borehole permeameter tests. Many empirical test methods
course of action. This document cannot replace education or
are used for calculating hydraulic conductivity from data
experienceandshouldbeusedinconjunctionwithprofessional
judgment. Not all aspects of this guide may be applicable in all
circumstances. This ASTM standard is not intended to repre-
1
ThisguideisunderthejurisdictionofASTMCommitteeD18onSoilandRock
sent or replace the standard of care by which the adequacy of
and is the direct responsibility of Subcommittee D18.21 on Groundwater and
a given professional service must be judged, nor should this
Vadose Zone Investigations.
CurrenteditionapprovedJuly1,2016.PublishedJuly2016.Originallyapproved
document be applied without consideration of a project’s many
ɛ1
in 1990. Last previous edition approved in 2010 as D5126–90(2010) . DOI:
unique aspects. The word “Standard” in the title of this
10.1520/D5126-16.
2
document means only that the document has been approved
The boldface numbers in parentheses refer to a list of references at the end of
the text. through the ASTM consensus
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: D5126/D5126M − 90 (Reapproved 2010) D5126/D5126M − 16
Standard Guide for
Comparison of Field Methods for Determining Hydraulic
1
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.
1
ε NOTE—The units statement in 1.6 and the designation were revised editorially in August 2010.
1. Scope Scope*
1.1 This guide covers a review of the test methods for determining hydraulic conductivity in unsaturated soils and sediments.
Test methods for determining both field-saturated and unsaturated hydraulic conductivity are described.
1.2 Measurement of hydraulic conductivity in the field is used for estimating the rate of water movement through clay liners
to determine if they are a barrier to water flux, for characterizing water movement below waste disposal sites to predict contaminant
movement, and to measure infiltration and drainage in soils and sediment for a variety of applications. Test methods are needed
−2 −8
for measuring hydraulic conductivity ranging from 1 × 10 to 1 × 10 cm/s, for both surface and subsurface layers, and for both
field-saturated and unsaturated flow.
1.3 For these field test methods a distinction must be is made between “saturated” (K ) and “field-saturated” (K ) hydraulic
s fs
conductivity. True saturated conditions seldom occur in the vadose zone except where impermeable layers result in the presence
of perched water tables. During infiltration events or in the event of a leak from a lined pond, a “field-saturated” condition
2
develops. True saturation does not occur due to entrapped air (1). The entrapped air prevents water from moving in air-filled pores
that, in turn, may reduce the hydraulic conductivity measured in the field by as much as a factor of two compared to conditions
when trapped air is not present (2). Field test methods should simulate the “field-saturated” condition.
1.4 Field test methods commonly used to determine field-saturated hydraulic conductivity include various double-ring
infiltrometer test methods, air-entry permeameter test methods, and borehole permeameter tests. Many empirical test methods are
used for calculating hydraulic conductivity from data obtained with each test method. A general description of each test method
and special characteristics affecting applicability is provided.
1.5 Field test methods used to determine unsaturated hydraulic conductivity in the field include direct measurement techniques
and various estimation methods. Direct measurement techniques for determining unsaturated hydraulic conductivity include the
instantaneous profile (IP) test method and the gypsum crust method. Estimation techniques have been developed using borehole
permeameter data and using data obtained from desorption curves (a curve relating water content to matric potential).
1.6 The values stated in either SI units or inch-pound units [presented in brackets] are to be regarded separately as standard.
The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other.
Combining values from the two systems may result in non-conformance with the as standard. No other units of measurement are
included in this standard.
1.6.1 The gravitational system of inch-pound units is used when dealing with inch-pound units. In this system, the pound (lbf)
represents a unit of force (weight), while the unit for mass is slugs. The rationalized slug unit is not given, unless dynamic (F =
ma) calculations are involved.
1.7 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice
D6026.
1.7.1 The method used to specify how data are collected, calculated, or recorded in this standard is not directly related to the
accuracy to which the data can be applied in design or other uses, or both. How one applies the results obtained using this standard
is beyond its scope.
1
This guide is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.21 on Groundwater and Vadose
Zone Investigations.
Current edition approved Aug. 1, 2010July 1, 2016. Published September 2010July 2016. Originally approved in 1990. Last previous edition approved in 200
...
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