ASTM D7499/D7499M-09

Standard Test Method for Measuring Geosynthetic-Soil Resilient Interface Shear Stiffness

SIGNIFICANCE AND USE
5.1 This test method is intended as a performance test to provide the user with a set of design values for the test conditions examined.
5.1.1 The test method is applicable to all geosynthetics and all soils when loaded in a cyclic manner.
5.1.2 This test method produces test data, which can be used in the design of geosynthetic-reinforced pavement structures or in applications where geosynthetics are subjected to cyclic loads.
5.1.3 The test results may also provide information related to the in-soil stress-strain response of a geosynthetic under confined loading conditions.
5.2 Information derived from this test may be a function of soil gradation, plasticity, as-placed dry unit weight, moisture content, length and surface characteristics of the geosynthetic and other test parameters. Therefore, results are expressed in terms of the actual test conditions. The test measures the net effect of a combination of interface shear mechanisms, which may vary depending on type of geosynthetic specimen, embedment length, relative opening size, soil type, displacement rate, normal stress, and other factors.
5.3 Information between laboratories on precision is incomplete. In cases of dispute, comparative tests to determine if there is a statistical bias between laboratories may be advisable.
SCOPE
1.1 This test method details how cyclic loading is applied to geosynthetics embedded in soil to determine the apparent stiffness of the soil–geosynthetic interface.
1.2 Resilient interface shear stiffness describes the shear stiffness between a geosynthetic and its surrounding soil under conditions of small cyclic loads.
1.3 This test method is intended to provide properties for design. The test method was developed for mechanistic empirical pavement design methods requiring input of the resilient interface shear stiffness. The use of this parameter from this test method for other applications involving cyclic loading should be evaluated on a case-by-case basis. It can also be used to compare different geosynthetics, soil types, etc., and thereby be used as a research and development test procedure.
1.4 The values stated in either SI units or inch-pound units 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 standard.
1.5 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 standard may involve hazardous materials, and equipment.

General Information

• Status: Historical
• Publication Date: 14-Jun-2009
• ICS: 59.080.70 - Geotextiles
• Technical Committee: D35 - Geosynthetics
• Drafting Committee: D35.01 - Mechanical Properties

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D7499/D7499M − 09
StandardTest Method for
Measuring Geosynthetic-Soil Resilient Interface Shear
Stiffness
This standard is issued under the fixed designation D7499/D7499M; 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 D3080 Test Method for Direct Shear Test of Soils Under
Consolidated Drained Conditions
1.1 This test method details how cyclic loading is applied to
D4439 Terminology for Geosynthetics
geosynthetics embedded in soil to determine the apparent
D4354 Practice for Sampling of Geosynthetics for Testing
stiffness of the soil–geosynthetic interface.
1.2 Resilient interface shear stiffness describes the shear
3. Terminology
stiffness between a geosynthetic and its surrounding soil under
3.1 For definitions of other terms used in this test method
conditions of small cyclic loads.
refer to Terminologies D123, D653, and D4439.
1.3 This test method is intended to provide properties for
3.2 Definitions of Terms Specific to This Standard:
design. The test method was developed for mechanistic em-
3.2.1 apertures, n—the open spaces in geogrids which
piricalpavementdesignmethodsrequiringinputoftheresilient
enable soil interlocking to occur.
interface shear stiffness. The use of this parameter from this
3.2.2 atmosphere for testing geosynthetics, n—air main-
test method for other applications involving cyclic loading
tained at a relative humidity of 60 6 10 % and a temperature
shouldbeevaluatedonacase-by-casebasis.Itcanalsobeused
of 21 6 2°C (70 6 4°F).
to compare different geosynthetics, soil types, etc., and thereby
be used as a research and development test procedure. 3.2.3 cross-machine direction, n—the direction in the plane
of the geosynthetic perpendicular to the direction of manufac-
1.4 The values stated in either SI units or inch-pound units
ture.
are to be regarded separately as standard. The values stated in
each system may not be exact equivalents; therefore, each 3.2.4 failure, n—an arbitrary point at which a material
ceases to be functionally capable of its intended use.
system shall be used independently of the other. Combining
values from the two systems may result in non-conformance
3.2.5 geosynthetic, n—a planar product manufactured from
with the standard.
polymeric material used with soil, rock, earth, or other geo-
1.5 This standard does not purport to address all of the technical engineering related material as an integral part of a
safety concerns, if any, associated with its use. It is the man-made project, structure, or system.
responsibility of the user of this standard to establish appro-
3.2.6 geosynthetic-soil resilient interface shear stiffness,
priate safety and health practices and determine the applica-
n—a parameter that describes the apparent stiffness of the
bility of regulatory limitations prior to use. This standard may
interface between the soil and the geosynthetic determined by
involve hazardous materials, and equipment.
calculating the slope of the shear stress, shear displacement
curve as the embedded geosynthetic is subjected to a cyclic
2. Referenced Documents
load.
2.1 ASTM Standards:
3.2.7 junction, n—the point where geogrid ribs are intercon-
D123 Terminology Relating to Textiles
nected in order to provide structure and dimensional stability.
D653 Terminology Relating to Soil, Rock, and Contained
3.2.8 machine direction, n—the direction in the plane of the
Fluids
geosynthetic parallel to the direction of manufacture.
This test method is under the jurisdiction of ASTM Committee D35 on 3.2.9 pullout, n—the movement of a geosynthetic over its
Geosynthetics and is the direct responsibility of Subcommittee D35.01 on Mechani-
entire embedded length, with initial pullout occurring when the
cal Properties.
back of the specimen moves, and ultimate pullout occurring
Current edition approved June 15, 2009. Published September 2009. DOI:
when the movement is uniform over the entire embedded
10.1520/D7499_D7499M-09.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
length.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
3.2.10 pullout force, (kN), , n—force required to pull a
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. geosynthetic out of the soil during a pullout test.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7499/D7499M − 09
3.2.11 pullout resistance, (kN/m), n—the pullout force per 5.2 Information derived from this test may be a function of
width of geosynthetic measured at a specified condition of soil gradation, plasticity, as-placed dry unit weight, moisture
displacement. content, length and surface characteristics of the geosynthetic
and other test parameters. Therefore, results are expressed in
3.2.12 rib, n—the continuous elements of a geogrid which
terms of the actual test conditions. The test measures the net
are either in the machine or cross-machine direction as
effect of a combination of interface shear mechanisms, which
manufactured.
may vary depending on type of geosynthetic specimen, em-
3.2.13 wire gage, n—a displacement gage consisting of a
bedment length, relative opening size, soil type, displacement
non extensible wire attached to the geosynthetic and monitored
rate, normal stress, and other factors.
by connection to a dial extensometer, or electronic displace-
5.3 Information between laboratories on precision is incom-
ment transducer.
plete. In cases of dispute, comparative tests to determine if
4. Summary of Test Method there is a statistical bias between laboratories may be advis-
able.
4.1 In this test method, a horizontal layer of geosynthetic is
embedded between two layers of soil. Six prescribed levels of
6. Apparatus
horizontal cyclic force are applied to the geosynthetic at five
6.1 Test Box—An open rigid box consisting of two smooth
specified levels of normal stress confinement. The maximum
parallel sides, a back wall, a horizontal split removable door, a
and minimum forces and corresponding displacements are
bottom plate, and a load transfer sleeve.The door is at the front
recorded for the last ten cycles of each combination of normal
as defined by the direction of applied cyclic force. A typical
stress and cyclic force (loading sequence).
box is shown in Fig. 1.
4.2 The resilient interface shear stiffness (kPa/m or psi/in)
6.1.1 The box should be square or rectangular with mini-
ofthetestspecimencanbecalculatedforanyloadingsequence
mum dimensions 457 mm (18 in.) long by 457 mm (18 in.)
by dividing the cyclic shear stress by the corresponding net
wide by 305 mm (12 in.) deep, if sidewall friction is mini-
recoverable horizontal displacement of the embedded geosyn-
mized, otherwise the minimum width should be 760 mm (30
thetic
in.). The dimensions should be increased, if necessary, so that
minimum width is the greater of 20 times the D85 of the soil
5. Significance and Use
or 6 times the maximum soil particle size, and the minimum
5.1 This test method is intended as a performance test to
length greater than 5 times the maximum geosynthetic aperture
provide the user with a set of design values for the test
size. The box shall allow for a minimum depth of 150 mm (6
conditions examined.
in.) above and below the geosynthetic. The depth of the soil in
5.1.1 The test method is applicable to all geosynthetics and
theboxaboveorbelowthegeosyntheticshallbeaminimumof
all soils when loaded in a cyclic manner.
6 times the D85 of the soil or 3 times the maximum particle
5.1.2 Thistestmethodproducestestdata,whichcanbeused
size of the soil, whichever is greater.The box must allow for at
in the design of geosynthetic-reinforced pavement structures or
least 305 mm (12 in.) embedment length beyond the load
in applications where geosynthetics are subjected to cyclic
transfer sleeve.
loads.
NOTE 1—To remove side wall friction as much as possible a high
5.1.3 The test results may also provide information related
density polyethylene (HDPE) geomembrane should be bonded to the
to the in-soil stress-strain response of a geosynthetic under
inside surfaces of the pullout box.The sidewalls may also be covered with
confined loading conditions. a layer of silk fabric, which has been shown to eliminate adhesion and has
FIG. 1 Side View of a Typical Test Device
D7499/D7499M − 09
a very low friction value. Alternatively, a lubricant can be spread on the
Measurementsoutsidethedoorattheboxentrancearemadeby
sidewalls of the box and thin sheets of polyethylene film used to minimize
electronic displacement transducers (e.g., linear variable dif-
the side wall friction. It should be also noted that the effect of sidewall
ferential transformers (LVDTs) can be used) mounted to the
friction on the soil-geosynthetic interface can also be eliminated if a
box frame to read against a plate attached to the specimen near
minimum distance is kept between the specimen and the side wall. This
the door.
minimum distance is recommended to be 150 mm (6 in.).
6.4.1 Displacement measurements within the box may em-
6.1.2 The box shall be fitted with a pair of metal sleeves
ploy any of several methods, which place sensors or gauge
(load transfer sleeves) at the entrance of the box to transfer the
connectors directly on the geosynthetic and monitor their
force into the soil to a sufficient horizontal distance so as to
change in location remotely. One such device utilizes wire
significantly reduce the stress on the door of the box. The
gages,whichareprotectedfromnormalstressbyasurrounding
sleeves shall consist of two tapered (illustrated in Fig. 3) or
tube, which runs from a location mounted on the specimen to
non-tapered (no more than 13 mm (0.5 in.) thick) plates
the outside of the box where displacements are measured by
extending the full width of the pullout box and into the pullout
displacement transducers.
box a minimum distance of 150 mm (6 in.), but it is
6.4.2 All electronic measurement devices must be accurate
recommendedthatthisdistanceequalthetotalsoildepthabove
or below the geosynthetic. Both design types must possess to 6 0.01 mm. Locations of the devices must be accurately
determined and recorded. Minimum extension capabilities of
taperededgesatthepointofloadapplicationinthesoilthatare
no more then 3 mm (0.12 in.) thick. The plates shall be rigidly 50 mm (2 in.) are recommended.
separated at the sides with spacers and be sufficiently stiff such 6.4.3 Determine the displacement of the geosynthetic at the
thatnormalstressisnottransferredtothegeosyntheticbetween
front (leading end) and the rear (embedded end) of the
the plates. geosynthetic at several locations along its width; suggested
layout is shown in Fig. 2
6.2 Normal Stress Loading Device—Normal stress applied
to the upper layer of soil above the geosynthetic must be
6.5 Geosynthetic Clamping Devices—Clamps which con-
constant and uniform for the duration of the load step. To
nect the specimen to the cyclic force system without slipping,
maintain a uniform normal stress, a flexible pneumatic or
causing clamp breaks or weakening the material may be used,
hydraulic diaphragm-loading device which is continuous over
see Note 2. The clamps shall be swiveled to allow the cyclic
the entire test box area should be used and capable of
forces to be distributed evenly throughout the width of the
maintaining the applied normal stress within 62% of the
sample. The clamps must allow the specimen to remain
required normal stress. Normal stresses utilized will depend on
horizontal during loading and not interfere with the interface
testing requirements; however, stresses up to 250 kPa (35 psi)
shear surface. Gluing, bonding, or otherwise molding of a
should be anticipated. A recommended normal stress-loading
geosynthetic within the clamp area is acceptable and recom-
device is an air bag.
mended whenever slippage might occur. Thin metal rods or
tubes may be used to reduce friction between the geosynthetic
6.3 Cyclic Force Loading Device—— Horizontal cyclic
clamp/sampleandthetopedgeofthelowerloadtransfersleeve
force must be supplied by a device with the ability to apply
(Fig. 3).
cyclic load in the direction of the opening of the box.The force
must be at the same level with the specimen.
NOTE 2— A suggested method of clamping is shown in Fig. 4 and
6.3.1 Thecyclicforcesystemmustbeabletoapplymultiple
includes a simple clamp consisting of two pieces of 22 gauge sheet metal
load repetitions using a haversine-shaped load pulse consisting glued to both sides of the geosynthetic sample. The sheet metal plates
should be at least the same width as the geosynthetic being tested. Special
of a 0.2 second load followed by a 0.80 second rest period.The
precautionsshouldbetakentoensurethatgeotextilesamplesadheretothe
loading system must also be able to simultaneously maintain a
sheet metal – such as making holes for the epoxy to flow through the
minimum seating load on the material during cyclic loading.
fabric, however; all such modifications to the fabric to facilitate bonding
6.3.2 Also, a device to measure the cyclic force (i.e., a load
should not interfere with the remainder of the geosynthetic protruding
cell)mustbeincorporatedintothesystemandshallbeaccurate from the front edge of the sheet metal.
within 60.5 % of its full-scale range.
6.6 Soil Preparation Equipment —Use equipment as neces-
6.4 Displacement Indicators— — Horizontal displacement sary for the placement of soils at desired conditions. This may
of the geosynthetic is measured at the entrance of the box and include compaction devices such as vibratory or “jumping-
at several locations on the embedded portion of the specimen. jack” type compaction, or hand compaction hammers. Soil
FIG. 2 Example Instrumentation Layout
D7499/D7499M − 09
FIG. 3 Side View of Load Transfer Sleeve Arrangement
FIG. 4 Geosynthetic Clamping Detail
container or hopper, leveling tools and soil placement/removal in.) and must allow for a minimum of 75 mm (3 in.) clearance
tools may be required.
on each side of the test specimen from the side walls of the test
box if the side wall friction is minimized (see Note 1),
6.7 Miscellaneous Equipment—Measurementandtrimming
otherwise the minimum clearance should be 150 mm (6 in.) on
equipment as necessary for geosynthetic preparation, a timing
each side. The length of the test specimen shall be of sufficient
devi
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