ASTM D6391-99
(Test Method)Standard Test Method for Field Measurement of Hydraulic Conductivity Limits of Porous Materials Using Two Stages of Infiltration from a Borehole
Standard Test Method for Field Measurement of Hydraulic Conductivity Limits of Porous Materials Using Two Stages of Infiltration from a Borehole
SCOPE
1.1 This test method covers field measurement of limiting values for vertical and horizontal hydraulic conductivities (also referred to as coefficients of permeability) of porous materials using the two-stage, cased borehole technique. These limiting hydraulic conductivity values are the maximum possible for the vertical direction and minimum possible for the horizontal direction. Determination of actual hydraulic conductivity values requires further analysis by qualified personnel.
1.2 This test method may be utilized for compacted fills or natural deposits, above or below the water table, that have a mean hydraulic conductivity less than or equal to 1X10-15 m/s (1X10-3 cm/s).
1.3 Hydraulic conductivity greater than 1X10-5 m/s may be determined by ordinary borehole tests, for example, U.S. Bureau of Reclamation 7310 (1); however, the resulting value is an apparent conductivity.
1.4 For this field test method, a distinction must be 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 (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 (3). This field test method simulates the "field-saturated" condition.
1.5 Experience with this test method has been predominantly in materials having a degree of saturation of 70 % or more, and where the stratification or plane of compaction is relatively horizontal. Its use in other situations should be considered experimental.
1.6 As in the case of all tests for hydraulic conductivity, the results of this test pertain only to the volume of soil permeated. Extending the results to the surrounding area requires both multiple tests and the judgment of qualified personnel. The number of tests required depends on among other things: the size of the area, the uniformity of the material in that area, and the variation in data from multiple tests.
1.7 The values stated in SI units are to be regarded as the standard unless other units specifically are given. By tradition in U.S. practice, hydraulic conductivity is reported in cm/s although the common SI units for hydraulic conductivity are m/s.
1.8 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. This test method does not purport to address environmental protection problems, as well.
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Designation: D 6391 – 99
Standard Test Method for
Field Measurement of Hydraulic Conductivity Limits of
Porous Materials Using Two Stages of Infiltration from a
Borehole
This standard is issued under the fixed designation D 6391; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 1.6 As in the case of all tests for hydraulic conductivity, the
results of this test pertain only to the volume of soil permeated.
1.1 This test method covers field measurement of limiting
Extending the results to the surrounding area requires both
values for vertical and horizontal hydraulic conductivities (also
multiple tests and the judgment of qualified personnel. The
referred to as coeffıcients of permeability) of porous materials
number of tests required depends on among other things: the
using the two-stage, cased borehole technique. These limiting
size of the area, the uniformity of the material in that area, and
hydraulic conductivity values are the maximum possible for
the variation in data from multiple tests.
the vertical direction and minimum possible for the horizontal
1.7 The values stated in SI units are to be regarded as the
direction. Determination of actual hydraulic conductivity val-
standard unless other units specifically are given. By tradition
ues requires further analysis by qualified personnel.
in U.S. practice, hydraulic conductivity is reported in cm/s
1.2 This test method may be utilized for compacted fills or
although the common SI units for hydraulic conductivity are
natural deposits, above or below the water table, that have a
–5
m/s.
mean hydraulic conductivity less than or equal to 1310 m/s
–3
1.8 This standard does not purport to address the safety
(1310 cm/s).
–5
concerns, if any, associated with its use. It is the responsibility
1.3 Hydraulic conductivity greater than 1310 m/s may be
of the user of this standard to establish appropriate safety and
determined by ordinary borehole tests, for example, U.S.
health practices and determine the applicability of regulatory
Bureau of Reclamation 7310(1) ; however, the resulting value
limitations prior to use. This test method does not purport to
is an apparent conductivity.
address environmental protection problems, as well.
1.4 For this field test method, a distinction must be made
between “saturated” (K ) and “field-saturated” (K ) hydraulic
s fs
2. Referenced Documents
conductivity. True saturated conditions seldom occur in the
2.1 ASTM Standards:
vadose zone except where impermeable layers result in the
D 653 Terminology Relating to Soil, Rock, and Contained
presence of perched water tables. During infiltration events or
Fluids
in the event of a leak from a lined pond, a “field-saturated”
D 1452 Practice for Soil Investigation and Sampling by
condition develops. True saturation does not occur due to
2 Auger Borings
entrapped air (2). The entrapped air prevents water from
D 1587 Practice for Thin-Walled Tube Geotechnical Sam-
moving in air-filled pores that, in turn, may reduce the
pling of Soils
hydraulic conductivity measured in the field by as much as a
D 2937 Test Method for Density of Soil in Place by the
factor of two compared to conditions when trapped air is not
Drive-Cylinder Method
present (3). This field test method simulates the “field-
D 3740 Practice for Minimum Requirements for Agencies
saturated” condition.
Engaged in the Testing and/or Inspection of Soil and Rock
1.5 Experience with this test method has been predomi-
as Used in Engineering Design and Construction
nantly in materials having a degree of saturation of 70 % or
D 5084 Test Method for Measurement of Hydraulic Con-
more, and where the stratification or plane of compaction is
ductivity of Saturated Porous Materials Using a Flexible
relatively horizontal. Its use in other situations should be
Wall Permeameter
considered experimental.
D 5092 Practice for Design and Installation of Ground
Water Monitoring Wells in Aquifers
D 5126 Guide for Comparison of Field Methods for Deter-
This test method is under the jurisdiction of ASTM Committee D-18 on Soil
mining Hydraulic Conductivity in the Vadose Zone
and Rock and is the direct responsibility of Subcommittee D18.04 on Hydrologic
Properties of Soil & Rock.
Current edition approved April 10, 1999. Published July 1999.
The boldface numbers in parentheses refer to the list of references at the end of
this standard. Annual Book of ASTM Standards, Vol 04.08.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6391–99
3. Terminology liners such as those used for retention ponds or storage tanks.
Due to the boundary condition assumptions used in deriving
3.1 Definitions—For definitions of terms used in this test
the equations for the limiting hydraulic ocnductivities, the
method, see Terminology D 653.
thickness of the unit tested must be at least six times the test
3.2 Definitions of Terms Specific to This Standard:
diameter. This requirement must be increased to eight test
3.2.1 horizontal conductivity, k , n—the hydraulic conduc-
h
diameters if the barrier is not underlain by a drainage blanket
tivity in (approximately) the horizontal direction.
or by a material far less permeable than the barrier being tested.
3.2.2 hydraulic conductivity, (coeffıcient of permeability) k,
5.3 The soil layer being tested must have sufficient cohesion
n—the rate of discharge of water under laminar flow conditions
to stand open during excavation of the borehole.
through a unit cross-sectional area of a porous medium under
5.4 This test method provides a means to measure infiltra-
a unit hydraulic gradient and standard temperature conditions
tion rate into a moderately large volume of soil. Tests on large
(20°C).
volumes of soil can be more representative than tests on small
3.2.2.1 Discussion—The term coeffıcient of permeability
volumes of soil. Multiple installations properly spaced provide
often is used instead of hydraulic conductivity, but hydraulic
a greater volume and an indication of spatial variability.
conductivity is used exclusively in this test method. A more
5.5 The data obtained from this test method are most useful
complete discussion of the terminology associated with Dar-
when the soil layer being tested has a uniform distribution of
cy’s law is given in the literature (4). It should be noted that
hydraulic conductivity and of pore space and when the upper
both natural soils and recompacted soils usually are not
and lower boundary conditions of the soil layer are well
isotropic with respect to hydraulic conductivity. Except for
defined.
unusual materials, k > k .
h v
5.6 Changes in water temperature can introduce significant
3.2.3 limiting horizontal conductivity, K2, n—the hydraulic
errors in the flow measurements. Temperature changes cause
conductivity as determined in Stage 2 of this test method,
fluctuations in the standpipe levels, which are not related to
assuming the tested medium to be isotropic. For ordinary soils,
flow. This problem is most pronounced when a small diameter
both compacted and natural, this is the minimum possible
standpipe is used in soils having hydraulic conductivities of 5
value for k .
h
–10
3 10 m/s or less.
3.2.4 limiting vertical conductivity, K1, n—the hydraulic
5.7 The effects of temperature changes are taken into
conductivity as determined in Stage 1 of this test method,
account by the use of a dummy installation, the temperature
assuming the tested medium to be isotropic. For ordinary soils,
effect gage (TEG). The base of the TEG must be sealed to
both compacted and natural, this is the maximum possible
prevent flow. The fluctuations of the TEG are due solely to
value for k .
v
ambient changes and are used to correct the readings at the
3.2.5 test diameter, n—the inside diameter (ID) of the
flowing tests.
casing.
3.2.6 vertical conductivity, k , n—the hydraulic conductiv- 5.8 If the soil being tested will later be subjected to
v
increased overburden stress, then the hydraulic conductivities
ity in (approximately) the vertical direction.
can be expected to decrease as the overburden stress increases.
Laboratory hydraulic conductivity tests or these tests under
4. Summary of Test Method
varying surface loads are recommended for studies of the
4.1 The rate of flow of water into soil through the bottom of
influence of level of stress on the hydraulic properties of the
a sealed, cased borehole is measured in each of two stages,
soil.
normally with a standpipe in the falling-head procedure. The
standpipe can be refilled as necessary.
NOTE 1—Notwithstanding the statements on precision and bias con-
4.2 In Stage 1, the bottom of the borehole is flush with the
tained in this standard: the precision of this test method is dependent on
the competence of the personnel performing it and the suitability of the
bottom of the casing for maximum effect of k . The test is
v
equipment and the facilities used. Agencies that meet the criteria of
continued until the flow rate becomes quasi-steady.
Practice D 3740 are generally considered capable of competent and
4.3 For Stage 2, the borehole is extended below the bottom
objective testing. Users of this test method are cautioned that compliance
of the casing for maximum effect of k . This stage of the test
h
with Practice D 3740 does not in itself assure reliable testing. Reliable
also is continued until the flow rate becomes quasi-steady.
testing depends on many factors; Practice D 3740 provides a means of
4.4 The direct results of the test are the limiting hydraulic
evaluating some of those factors.
conductivities K1 and K2. The actual hydraulic conductivities
6. Apparatus
k and k can be calculated from these values (5).
v h
6.1 Boring/Reaming Tools:
5. Significance and Use
6.1.1 Drilling Equipment—Equipment must be available to
5.1 This test method provides a means to measure both the advance the borehole to the desired test level. This borehole
maximum vertical and minimum horizontal hydraulic conduc- diameter must be at least 5 cm (2 in.) larger than the outside
tivities, especially in the low ranges associated with fine- diameter of the casing. The auger or bit used to advance the
–7 –11
grained clayey soils, 1310 m/s to 1310 m/s. borehole below the casing for Stage 2 shall have a diameter
5.2 This test method particularly is useful for measuring about 1 cm ( ⁄2 in.) less than the inside diameter of the casing.
liquid flow through soil moisture barriers such as compacted For tests in compacted materials above the water table, and
clay liners or covers used at waste disposal facilities, for canal wherever else possible, the borehole shall be advanced by dry
and reservoir liners, for seepage blankets, and for amended soil augering. Either hand or mechanical augers are acceptable.
D6391–99
6.1.2 Flat Auger—The flat auger (see Fig. 1) is used to prepare the borehole for casing installation. It shall be capable
FIG. 1 Flat Bottom Reaming Auger
D6391–99
of reaming the bottom of the borehole to a level plane diameter of pellets or granules selected should be less than one
perpendicular to the borehole axis. The flat auger shall have a fifth the width of the annular space into which they are placed.
diameter about 5 cm (2 in.) larger than the outside diameter of
The directly placed sealant shall extend to the ground surface
the casing.
or to a minimum of1m(3ft) above the bottom of the casing,
6.1.3 Reamer—The reamer (see Fig. 1) is used to complete
whichever is lesser. Either the placed sealant or the grouted
the Stage 2 cavity. The base of the reamer shall be capable of
sealant shall extend to the ground surface.
reaming the bottom of the advanced borehole to a level plane,
6.2.3.2 Grouted Sealant—The annular space may be
perpendicular to the borehole axis, and having the inside
grouted above the placed sealant. Any of the grouting methods
diameter of the casing. The bottom plate of the reamer shall
specified in Practice D 5092 may be used.
have a diameter about 0.1 cm (0.04 in.) less than the inside
6.2.3.3 Sock—The sock protects the soil at the bottom of the
diameter of the casing. The vertical side of the cutting plate
casing from disturbance when water is introduced and prevents
shall be serrated.
collapse of the Stage 2 cavity. It is a cylinder composed of a
6.1.4 Scarifier—A bent fork, wire brush, or similar rough-
semi-rigid, porous sidewall and bottom (such as a geogrid),
ener small enough to fit easily within the casing and having a
lined with a geotextile, and filled with pea gravel or other
handle long enough to reach the bottom of Stage 2, is used to
highly pervious material. The hydraulic conductivity of all
roughen the walls of the Stage 2 cavity.
sock materials shall be at least ten times the anticipated
6.2 Borehole Casing:
hydraulic conductivity of the tested stratum in the horizontal
6.2.1 Casing—The casing shall be watertight but may be of
direction. The outer diameter is 0.6 cm ( ⁄4 in.) less than the
any material or diameter. Its minimum ID shall be 10 cm (4 in.)
inner diameter of the casing. The length is approximately 8 cm
unless the clearance provisions specified in 7.7 cannot be met.
(3 in.) longer than will be the borehole extension for Stage 2.
In such cases only, the ID may be reduced to 7.5 cm (3 in.). The
Wires or other suitable means for retrieving the sock should be
wall thickness shall be adequate to prevent collapse under the
provided.
lateral pressure of the overburden and swelling bentonite.
Standard 10-cm (4-in.) ID Schedule 40 PVC threaded pipe is
6.3 Pressure/Flow System:
satisfactory. The bottom of the casing shall be cut off smooth
6.3.1 Flow Control System—The plumbing for the flow
and square. The casing shall have flush threads; external
control system is illustrated on Fig. 2. It can be composed of
couplers interfere with sealing the annulus and internal cou-
metal or plastic components. All flow system components shall
plers with advancing the borehole for Stage 2. Neither shall be
have a diameter of at least 75 % that of the standpipe. Nominal
used. The top of the casing shall be provided with a means of
13-mm (0.5-in.) components have been satisfactory for 10-cm
attaching the top assembly. Typical modifications include
(4-in.) diameter tests.
threading the top or attaching a flange. When threads are used,
6.3.2 Standpipe—The standpipe, also shown on Fig. 2,
they must be flush. When a flange is used,
...
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