ASTM D8269-21

Standard Guide for the Use of Geocells in Geotechnical and Roadway Projects

SIGNIFICANCE AND USE
5.1 This guide covers applications, support mechanisms, and design principles associated with geocells to help designers and engineers determine when and how to appropriately use this technology.  
5.2 A better understanding of the key design principles, material properties, mechanisms of improvement, and methodologies will help engineers and owners interested in using geocells understand the most efficient and appropriate ways to utilize this type of ground improvement for a variety of geotechnical-related applications.  
5.3 This guide does not preclude the judgment and practice of those competent in geotechnical design.
SCOPE
1.1 This guide is intended to cover basic considerations for the use of geocells in various geotechnical and roadway projects to bring a unified understanding of efficient and appropriate ways to utilize this type of ground improvement technology for a variety of geotechnical-related applications, including but not limited to: load support for pavements, subgrade improvement, slope stability, retaining walls, earth retention, and slope and channel protection. Engineers and owners interested in using this manufactured product can refer to the information in this guide to learn about key design principles, properties, mechanisms, and methodologies for applicable geotechnical applications. Geotechnical designs that incorporate geocells should take into consideration the specific attributes of each product. The engineer is encouraged to utilize design methodologies based on reliable test results and research.  
1.2 This guide offers a collection of information and does not recommend a course of action. This guide cannot replace education or experience, and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances.  
1.3 This guide is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this guide be applied without consideration of a project’s many unique aspects.  
1.4 The word “standard” in the title of this guide means only that this guide has been approved through the ASTM International consensus process.  
1.5 The values given in SI units are to be regarded as standard. Values in parentheses are for information only.  
1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 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.

General Information

• Status: Published
• Publication Date: 14-Jul-2021
• ICS: 93.080.01 - Road engineering in general
• Technical Committee: D35 - Geosynthetics
• Drafting Committee: D35.01 - Mechanical Properties

Relations

• Refers: ASTM E2254-24 - Standard Test Method for Storage Modulus Calibration of Dynamic Mechanical Analyzers
• Effective Date: 15-Mar-2024
• Refers: ASTM D4439-24 - Standard Terminology for Geosynthetics
• Effective Date: 01-Feb-2024
• Refers: ASTM D6392-23 - Standard Test Method for Determining the Integrity of Nonreinforced Geomembrane Seams Produced Using Thermo-Fusion Methods
• Effective Date: 01-Nov-2023
• Refers: ASTM D5397-20 - Standard Test Method for Evaluation of Stress Crack Resistance of Polyolefin Geomembranes Using Notched Constant Tensile Load Test
• Effective Date: 01-Jun-2020
• Refers: ASTM D5397-19a - Standard Test Method for Evaluation of Stress Crack Resistance of Polyolefin Geomembranes Using Notched Constant Tensile Load Test
• Effective Date: 15-Oct-2019
• Refers: ASTM D5199-12(2019) - Standard Test Method for Measuring the Nominal Thickness of Geosynthetics
• Effective Date: 15-Jun-2019
• Refers: ASTM D5397-19 - Standard Test Method for Evaluation of Stress Crack Resistance of Polyolefin Geomembranes Using Notched Constant Tensile Load Test
• Effective Date: 01-Jan-2019
• Refers: ASTM D4439-18 - Standard Terminology for Geosynthetics
• Effective Date: 15-Apr-2018
• Refers: ASTM D6392-12(2018) - Standard Test Method for Determining the Integrity of Nonreinforced Geomembrane Seams Produced Using Thermo-Fusion Methods
• Effective Date: 01-Feb-2018
• Refers: ASTM D4439-17 - Standard Terminology for Geosynthetics
• Effective Date: 01-Aug-2017
• Refers: ASTM D7238-06(2017) - Standard Test Method for Effect of Exposure of Unreinforced Polyolefin Geomembrane Using Fluorescent UV Condensation Apparatus
• Effective Date: 01-Jul-2017
• Refers: ASTM D4439-15a - Standard Terminology for Geosynthetics
• Effective Date: 01-Sep-2015
• Refers: ASTM D4439-15 - Standard Terminology for Geosynthetics
• Effective Date: 01-Jul-2015
• Refers: ASTM D6992-03(2015) - Standard Test Method for Accelerated Tensile Creep and Creep-Rupture of Geosynthetic Materials Based on Time-Temperature Superposition Using the Stepped Isothermal Method
• Effective Date: 01-May-2015
• Refers: ASTM D5885/D5885M-15 - Standard Test Method for Oxidative Induction Time of Polyolefin Geosynthetics by High-Pressure Differential Scanning Calorimetry
• Effective Date: 01-May-2015

Overview

ASTM D8269-21: Standard Guide for the Use of Geocells in Geotechnical and Roadway Projects provides comprehensive guidance for engineers and project owners on the effective and efficient implementation of geocells as a ground improvement technology. Geocells are three-dimensional, polymeric structures formed by interconnected strips that create a cellular confinement system. This standard addresses their applications, design considerations, support mechanisms, and essential properties, supporting a unified understanding of their use in load support, subgrade improvement, slope stability, retaining walls, earth retention, and channel protection for both geotechnical and roadway projects.

Key Topics

• Geocell Structure and Function: Geocells, when opened, create a network of interconnected cells that can be filled with soils, aggregates, concrete, or recycled materials. Lateral confinement provided by geocell walls enhances the mechanical properties of weak or variable materials, reducing settlement and improving load distribution.
• Design Principles: The selection and use of geocells require consideration of cell geometry, material attributes (tensile strength, stiffness, creep resistance), connection methods, and environmental durability (resistance to UV, chemicals, and stress cracking).
• Performance Mechanisms: Geocells enhance ground performance through the mattress or slab effect, which results from the lateral restraint of infill, improved stiffness of the stabilized layer, and increased shear resistance.
• Material and Installation: Geocells can be made from different polymers or geotextiles, which influence their performance and compatibility with various infill types. Installation requires attention to cell expansion, proper anchoring, and compaction practices to maintain system integrity.

Applications

Geocells, as described in ASTM D8269-21, are versatile and can be used in a variety of geotechnical applications, making them valuable in infrastructure and civil engineering projects:

• Load Support for Pavements: Geocells distribute loads and improve the performance of unpaved and paved roads, railways, ports, and heavy-duty pavements by stabilizing subgrade and reducing vertical deformations.
• Subgrade Improvement: By confining inferior or variable soils, geocells increase bearing capacity and reduce construction depth requirements.
• Slope Stability and Erosion Control: Used on slopes and channels, geocells provide erosion protection, support vegetated facings, and resist tractive forces from water flow.
• Retaining Walls and Earth Retention: Geocells form gravity walls, reinforced slopes, and vertical facings that retain soil masses and withstand lateral earth pressures.
• Channel Protection: Geocell systems stabilize lining materials against hydraulic forces in drainage and water conveyance structures.

Proper application of geocells can result in cost savings, reduced construction times, improved sustainability by enabling the use of locally sourced or recycled materials, and extended infrastructure lifespan.

Related Standards

Implementing ASTM D8269-21 often involves reference to other standards for specification, testing, and terminology:

• ASTM D4439 - Terminology for Geosynthetics
• ASTM D1693 - Environmental Stress-Cracking of Ethylene Plastics
• ASTM D4595 - Tensile Properties of Geotextiles
• ASTM D5262, D6992 - Creep and Creep Rupture of Geosynthetics
• ASTM D5721, D5885 - Aging and Oxidative Induction Time for Polyolefin Geosynthetics
• ISO 6721-1, ISO 10319, ISO 13426-1 - Mechanical properties and testing methods specific to geosynthetics and geocells

Why ASTM D8269-21 Matters

Adhering to ASTM D8269-21 aids in ensuring safe, efficient, and long-lasting geocell installations for ground improvement in geotechnical and roadway projects. It enables informed design decisions based on material properties, field conditions, and established testing methods, contributing to project quality and structural reliability.

Keywords: ASTM D8269-21, geocells, geotechnical engineering, ground improvement, roadway projects, load support, slope stability, retaining walls, channel protection, geosynthetics.

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.
Designation: D8269 − 21
Standard Guide for the
Use of Geocells in Geotechnical and Roadway Projects
This standard is issued under the fixed designation D8269; 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 1.7 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This guide is intended to cover basic considerations for
ization established in the Decision on Principles for the
the use of geocells in various geotechnical and roadway
Development of International Standards, Guides and Recom-
projects to bring a unified understanding of efficient and
mendations issued by the World Trade Organization Technical
appropriate ways to utilize this type of ground improvement
Barriers to Trade (TBT) Committee.
technology for a variety of geotechnical-related applications,
including but not limited to: load support for pavements,
2. Referenced Documents
subgrade improvement, slope stability, retaining walls, earth
retention, and slope and channel protection. Engineers and 2
2.1 ASTM Standards:
owners interested in using this manufactured product can refer
D1693 Test Method for Environmental Stress-Cracking of
to the information in this guide to learn about key design
Ethylene Plastics
principles, properties, mechanisms, and methodologies for
D3895 Test Method for Oxidative-Induction Time of Poly-
applicablegeotechnicalapplications.Geotechnicaldesignsthat
olefins by Differential Scanning Calorimetry
incorporate geocells should take into consideration the specific
D4355/D4355M Test Method for Deterioration of Geotex-
attributes of each product. The engineer is encouraged to
tiles by Exposure to Light, Moisture, and Heat in a Xenon
utilize design methodologies based on reliable test results and
Arc-Type Apparatus
research.
D4439 Terminology for Geosynthetics
1.2 This guide offers a collection of information and does
D4595 Test Method for Tensile Properties of Geotextiles by
not recommend a course of action. This guide cannot replace
the Wide-Width Strip Method
education or experience, and should be used in conjunction
D5199 Test Method for Measuring the Nominal Thickness
with professional judgment. Not all aspects of this guide may
of Geosynthetics
be applicable in all circumstances.
D5262 Test Method for Determining the Unconfined Ten-
sion Creep and Creep Rupture Behavior of Planar Geo-
1.3 This guide is not intended to represent or replace the
synthetics Used for Reinforcement Purposes
standard of care by which the adequacy of a given professional
D5397 Test Method for Evaluation of Stress Crack Resis-
service must be judged, nor should this guide be applied
without consideration of a project’s many unique aspects. tance of Polyolefin Geomembranes Using Notched Con-
stant Tensile Load Test
1.4 Theword“standard”inthetitleofthisguidemeansonly
D5721 Practice forAir-OvenAging of Polyolefin Geomem-
that this guide has been approved through the ASTM Interna-
branes
tional consensus process.
D5885/D5885M Test Method for Oxidative Induction Time
1.5 The values given in SI units are to be regarded as
of Polyolefin Geosynthetics by High-Pressure Differential
standard. Values in parentheses are for information only.
Scanning Calorimetry
D5994/D5994M TestMethodforMeasuringCoreThickness
1.6 This standard does not purport to address all of the
of Textured Geomembranes
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- D6392 Test Method for Determining the Integrity of Nonre-
priate safety, health, and environmental practices and deter- inforced Geomembrane Seams Produced Using Thermo-
mine the applicability of regulatory limitations prior to use. Fusion Methods
1 2
ThisguideisunderthejurisdictionofASTMCommitteeD35onGeosynthetics For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and is the direct responsibility of Subcommittee D35.01 on Mechanical Properties. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Current edition approved July 15, 2021. Published August 2021. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
D8269-21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8269 − 21
D6992 Test Method for Accelerated Tensile Creep and 5. Significance and Use
Creep-Rupture of Geosynthetic Materials Based on Time-
5.1 This guide covers applications, support mechanisms,
Temperature Superposition Using the Stepped Isothermal
anddesignprinciplesassociatedwithgeocellstohelpdesigners
Method
and engineers determine when and how to appropriately use
D7238 Test Method for Effect of Exposure of Unreinforced
this technology.
Polyolefin Geomembrane Using Fluorescent UV Conden-
5.2 A better understanding of the key design principles,
sation Apparatus
material properties, mechanisms of improvement, and method-
E2254 Test Method for Storage Modulus Calibration of
ologies will help engineers and owners interested in using
Dynamic Mechanical Analyzers
geocells understand the most efficient and appropriate ways to
2.2 ISO Standards:
utilize this type of ground improvement for a variety of
ISO 6721-1 Plastics—Determination of Dynamic Mechani-
geotechnical-related applications.
cal Properties—Part 1: General Principles
5.3 This guide does not preclude the judgment and practice
ISO 10319 Geosynthetics—Wide-Width Tensile Test
of those competent in geotechnical design.
ISO 13426-1 Geotextiles and Geotextile-Related Products—
StrengthofInternalStructuralJunctions—Part1:Geocells
6. Overview of the Geocell Technology and Basic
2.3 GRI Standards:
Construction Considerations
GRI GS13 Guide for Geomembrane-Related Geocell Seam
6.1 Geocells are supplied as a group of connected strips
Strength and Its Efficiency with Respect to the Perforated
(referred to as a “panel” or “section”) that, when opened, form
Sheet Strength
anetworkofopencells(seeFig.1).Individualgeocellsections
GRI GS15 Specification for Test Methods, Test Properties
can be connected using suitable, manufacturer-approved con-
and Testing Frequency for Geocells Made from High
nectiondevicesthatprovidesufficientstrengthtopreventpanel
Density Polyethylene (HDPE) Strips
separation during installation and throughout the entire design
life. Geocells may differ in terms of their basic physical and
3. Terminology
material characteristics, including but not limited to: open
3.1 Definitions—For definitions of common geosynthetics cell/section dimensions, number of cells per unit area (cell
terms used in this guide, refer to Terminology D4439. density), cell depth (height), or presence/absence of perfora-
tions or texture. Geocells have been used successfully in
3.2 Definitions of Terms Specific to This Standard:
practice since the 1980s. Selection of a geocell product should
3.2.1 geocell, n—a three-dimensional, compartmentalized,
be based on a detailed evaluation of project-specific needs and
polymeric structure having discrete cells that are formed by
circumstances as performed by a geotechnical engineer or
expanding the structure, that is subsequently filled with soil,
other qualified professional, and geocell use should be consis-
aggregate, concrete, pulverized debris, recycled asphalt
tent with the manufacturer’s recommendations that are based
pavement, or other infill material for geotechnical applications
on reliable test results and research (1, 2).
such as: (1) load support for unpaved and paved roads,
railways, ports, heavy-duty pavements, container yards, and 6.2 Individual cells consist of two strips that are connected
basal embankment stabilization; (2) retaining structures, free- together on either end, and held open prior to filling through
standing structures, and fascia walls; and (3) slope, channel, lateral forces applied to the cell walls from the adjacent sets of
and geomembrane protection. cell walls that are connected to them. In application, two types
of hoops are present in any configuration that involves the
4. Summary of Guide installation of multiple adjoining geocell panels.These include
factory-welded hoops, and mechanically joined hoops using
4.1 This guide covers some of the major considerations
manufacturer-recommended methods (refer to 6.5). Located
associated with the design of geotechnical projects where the
within the body of individual geocell panels, factory-welded
soil, aggregate, concrete, or other infill materials may be
hoops consist of the cell wall material and the seams on either
improved through the three-dimensional mechanical stabiliza-
end. Located around the perimeter of the individual geocell
tion of geocells.
panels, mechanically joined hoops are formed in the field
4.2 Common geocell applications include: (1) load support
during connection of adjoining panels. The primary mecha-
for unpaved and paved roads, railways, ports, heavy-duty
nism by which geocells provide benefit is through lateral
pavements, container yards, and basal embankment stabiliza-
confinement of the infill; therefore, it is necessary that the
tion; (2) retaining structures, free-standing structures, and
entire hoop of material that makes up each individual cell and
fascia walls; and (3) slope, channel, and geomembrane protec-
the connection devices remains intact during construction and
tion.
throughout the life of the structure. The entire hoop, including
the seams, must remain intact and be sufficiently strong to
carry the applied hoop stresses without breaking, deforming
excessively, relaxing, or degrading during construction and for
Available from International Organization for Standardization (ISO), ISO
Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
Switzerland, https://www.iso.org.
4 5
Available from Geosynthetic Institute (GSI), 475 Kedron Ave, Folsom, PA The boldface numbers in parentheses refer to a list of references at the end of
19033, https://www.geosynthetic-institute.org. this standard.
D8269 − 21
FIG. 1 Plan View and 3D View of Geocells
(layout of perforations in 3D view may vary between different manufacturers)
the entire design life of the structure. Any of these failure system is similarly influenced by these factors, along with the
modes in either the cell wall, seams, or connectors will allow geometry of the machine-welded geocells (which are not
the infill to expand laterally, rendering individual cells or the exactly circular shaped, as shown in Fig. 1); the number of
entire geocell layer ineffective. adjacent geocells acting in response to an applied load; and the
stiffness of system components. In general, with increasing
6.3 Lateral restraint (or confinement) of the infill material is
numbers of adjacent cells (cell density) surrounding the loca-
provided by the hoop of material that forms the cell wall, and
tion of an applied load, the resulting horizontal pressure is
the improved lateral support of adjacent cells (that is, the
distributed over a wider area. Emersleben and Meyer (7)
slab/mattress effect), as reported in Refs (3-6). The suitability
observed that the horizontal pressure in a single cell was
of the geocell in specific design cases and the magnitude of
distributed to the 24 closest surrounding cells, exemplifying
confinement provided by the geocell are directly dependent on
the mattress effect of the composite behavior. Individual cells
the key material properties outlined in 6.8, the geometry of the
limit lateral movement of the infill, which reduces vertical
individual cells, and the position of the geocell layer within the
settlement and increases stiffness within the reinforced layer.
geotechnical structure.
As these individual cells work in concert with other adjacent
6.4 The mattress effect mentioned in 6.3 relies on the
cells(thatis,themattresseffect),appliedloadsaremorewidely
composite behavior of an integrated infill-geocell system in
spread, resulting in a more uniform distribution of applied
which lateral earth pressures are mobilized and transferred
stresses as well as a reduction in the magnitude of these
across a three-dimensional network of interconnected cells. In
stresses to underlying layers, the result of which is a decrease
this regard, the properties of the infill material (that is, particle
in the overall settlement and a reduction in differential settle-
size/distribution, angle of internal friction, relative density,
ment.
etc.) act in conjunction with the discrete elements/
characteristics of the geocell material (comprised of cell walls, 6.5 Asingle group of geocells has a finite length and width
seams/joints, connection devices, perforations/texture, and in depending on how it was manufactured. As mentioned in 6.1,
some cases, earth anchoring devices) to facilitate the desired a larger continuous area can be covered by attaching single
ground improvement effect. The infill materials, along with groups of geocells to one another from end to end, side to side,
each of the above-referenced discrete elements of the geocell or both. Common methods of attachment include stapling and
system, will each impart some level of influence over system lockingdevices,aswellastheuseofspecializedmanufacturer-
performance. Accordingly, the behavior of the composite specific connection devices. Manufacturer’s recommendations
D8269 − 21
for attachment should be followed as long as they are durable hoop of material forming the cellular structure must remain
and provide sufficient connection strength, pullout/separation intact to ensure adequate performance throughout the design
resistance, resistance to lateral and vertical movement, and
life, including both factory-welded hoops and hoops formed as
resistance to node rotation between subsequent geocell groups.
a result of connections between adjacent panels.
6.6 Geocell section opening size in the field is determined
6.9 Consideration should be given to the environmental
by the distance that the geocell is stretched from side to side.
conditionsassociatedwiththedesign.Theseconditionsinclude
For typical load support projects, geocells are temporarily held
temperature, chemical or environmental contamination, sub-
open by staking the edges in a manner that ensures that all
merged conditions, prolonged exposure to sunlight, seismic
geocell openings can be filled. Stakes can be left in place or
activity, etc. The material properties of the geocell should be
removed and reused as the construction advances. Slope and
evaluated under the expected conditions to ensure proper
channel protection applications typically require that perma-
performance throughout the design life. Tests are available to
nent stakes, tendons, or both, be installed to hold the geocells
evaluate environmental stress cracking resistance (ESCR),
in place. Temporary staking, bent frames, or both are typically
corrosion resistance (particularly for staples or other types of
used to hold geocells open for retaining wall applications.
metal connectors), and resistance to ultraviolet and oxidation
6.7 The bulk of the background and research information
degradation.
used to develop this guide is based on geocells made of
6.10 Infill material can include most types of non-plastic
extruded plastic strips. Geocells are also made of nonwoven
soils and sand, granular fills, concrete, and recycled materials.
geotextiles (as shown in Fig. 2) and, where appropriate,
In pavement and retaining wall applications a free-draining
specific guidelines for these materials are also included in the
guide. It is important to note that geocells made from different granular fill is typically used, having a wide range of quality,
types of materials, sizes, strengths, etc. may behave or perform including uniformly graded aggregates and recycled materials.
differently from one another; therefore, it is important to
Reinforced slope applications may require a graded, free-
understand and utilize proper material properties that relate to
draining granular fill. Topsoil can be used in the outer cell if a
its performance for each of the applications outlined below.
vegetated fascia is desired. Topsoil, aggregate, and concrete
Manufacturer’s recommendations for each material type
can be used as infill for channel protection. The type of infill
should be based on reliable test results and research for their
should be based on the slope angle and channel hydraulic
specific material.
conditions. Vegetated topsoil is often used in slope protection
applications. Generally, geocells provide higher benefit when
6.8 The polymeric properties of the geocell are directly
lower quality infill is used because the level of improvement
related to its performance throughout the entire project design
life (3). These properties include tensile strength, tensile compared to fill alone is greater. Nevertheless, the use of
stiffness, resistance to plastic deformation or creep, hoop geocells with high-quality granular layers (in particular for
strength, and environmental durability (as outlined in 6.9). surfacetransportationapplications)mayalsoleadtosignificant
Because geocells act cooperatively due to the proximity of improvement of surface support with lower deflections, ex-
surrounding cells (that is, mattress effect, see 6.4), it is also
tended life in terms of increased traffic, or both. Greater
important to assess the performance benefits imparted to the
load-carrying capacity, reduced thicknesses of the structural
entire layer in which the geocell is employed. Accelerated
layers,extendedlife,orcombinationsthereofcanberealizedin
methods are available to evaluate and verify long-term perfor-
roadway applications through the use of geocells with a wide
mance of the geocell system itself and as part of a complete
range of infill quality including inferior materials, which may
solution(forexample,rollingwheelloadtests,cyclicplateload
reduce overall project cost and reduce construction time (5).
tests,andfull-scalelaboratorytestsections) (7-9).Triaxialtests
6.11 Filling should be done without driving directly on the
have also been used to evaluate and understand the strength
unfilled geocells to avoid damage. Construction equipment can
propertiesofthecompositegeocell-soilsystem (10).Theentire
advance onto the geocells once the infill material is deep
enough to prevent equipment from directly contacting the top
of the geocell. The drop height of infill material into the cells
should be limited to prevent panel distortion. Overfill material
thickness should be determined based on the design or
experience, or both, and should be compacted together with
geocell infill material.
6.12 Compaction should be done in a manner that prevents
damage to the geocell but thoroughly densifies the infill
material with sufficient energy to ensure that further densifica-
tion during the life of the structure is minimized and that hoop
stressesinthegeocellwallsareengaged.Vibratorycompaction
is generally preferred in load support applications to ensure the
geocell infill is adequately densified. Sheepsfoot rollers should
FIG. 2 Nonwoven Geotextile-Based Geocell not be used to compact materials within the geocell-stabilized
D8269 − 21
concern. In this case, restricting the accumulated permanent strain in the
layer. Compaction requirements may vary depending on the
geocell will ensure that the geocell layer limits settlement, which will
specific application, and manufacturer’s instructions should be
minimize distortion and maintain acceptable performance of the stabilized
consulted.
system throughout the design life.
6.13 The primary benefit of geocells used in load support
6.15 Whether or not geocells are used, depending on the
and roadway projects is through increased stiffness of the
gradation of the support materials beneath the granular/geocell
stabilized layer achieved by a reduction in volumetric changes
layer, it may be necessary to include a geosynthetic separation
of the infill during loading by means of lateral confinement
layer to prevent the migration of fines into the stabilized layer
provided by the geocell. The geocell-enhanced layers are
or punching of the infill material into softer layers beneath, or
improved through the addition of tensile strength at low strain
both.
levels provided by the geocell hoop. The cellular structure
6.16 Geocells made of extruded plastic strips are typically
limitstheverticalsettlementsofthestabilizedinfillbylaterally
perforated and textured, while geocells made from geotextiles
restricting movement of the individual particles (that is, lateral
are oftentimes not perforated. Water flow through geocells
confinement). The ability to maintain low permanent deforma-
made from nonwoven materials depends on their permittivity.
tion levels from applied loads and provide long-term, stable
The configuration of perforations or hole diameters, or combi-
(that is, elastic) confinement of the infill material is directly
nations thereof, in the geocell should ensure adequate confine-
dependentontheabilityofthegeocelltoretainitskeymaterial
ment of the infill. Having a distribution of perforations en-
properties (refer to 6.8) and dimensions throughout the design
hances the friction and interlocking of the infill soil and
life. The mattress effect (described in 6.4) allows for improved
reduces stress concentrations, leading to better confinement
load transfer and distribution to underlying layers. The ability
and improved effectiveness of lateral drainage.
of the reinforced layer to maintain low permanent deformation
levelsfromappliedloadsandprovidelong-term,stable(thatis,
7. Design Applications
elastic) confinement of the infill material is also dependent on
7.1 Geocells Used as Load Support for Unpaved and Paved
the ability of the composite system to effectively translate
Roads, Railways, Ports, Heavy-Duty Pavements, and Basal
applied loads into lateral earth pressures, which are then
Embankment Stabilization:
distributed across a three-dimensional network of intercon-
7.1.1 Geocells used in this application are commonly de-
nected cells. An elastic response of the improved layer can be
ployed on a horizontal surface using one or more layers to
achieved by limiting loads in the cell walls or seams (or both)
strengthen, stabilize, or enhance the load-carrying capability of
belowapredeterminedthreshold,becauseexcessivepermanent
the trafficked surface, or to enable the use of inferior infill
plastic deformation over the design life or rupture of the seams
materials (typically granular and non-plastic materials such as
or cell walls, or both, will limit the benefit of the geocell or
sand, poorly graded aggregates, local weak and marginal
cause the structure to fail.
non-plastic soils, recycled asphalt pavement, and other waste
6.14 The volume of infill material that can be accommo- products including pond ash, etc.) (12). Load support improve-
ment is provided through a three-dimensional matrix of inter-
dated within individual cells is directly related to the length of
hoop of material that forms the cell wall (that is, the cell size) connected cell walls that provide tensile strength (pseudo-
cohesion) to unbound materials used as infill, resulting in a
and its height. Changes in the height of the geocell are
negligible, so settlement of the infill over time is primarily a stiffer stabilized layer. Other key improvements provided by
the geocell are the reduction of vertical settlements,
factor of the length of the wall perimeter or geocell hoop.
Performance of the geocell depends on the ability of individual deformation, or both by limiting volumetric changes within the
infill material and added flexural strength of the geocell/infill
hoops (formed either by mechanical welding or mechanical
joining) to remain intact and to resist stretching during con- composite system (7).
struction and throughout the life of the structure. Limiting 7.1.2 The primary support mechanism of geocells in load
strain in the geocell hoop is the primary mechanism that support applications (for example, roads, railroads, port load-
restrains particle movement within each cell in the lateral ing platforms, etc.) is accomplished through durable lateral
direction (that is, lateral confinement), and results in a direct restraint of soil particles submitted to vertical loads from
reduction of the vertical displacement of the infill (11),as vehicles, as described in 6.3, 6.4, and 6.13. This support
mechanism provides a reduction in vertical stress transfer to
explained in Note 1. A second and important mechanism that
helps restrict lateral movements within the geocell layer is the layers beneath and increased support to layers above through-
out the entire design life of the structure.
increased lateral support provided by adjacent cells (that is, the
slab/mattress effect), as reported in Refs (3-6) and further 7.1.2.1 In this application, the cell wall perimeter should be
designed to limit the permanent (that is, plastic) hoop strain
discussed in 6.4.
over the entire design life in order to limit vertical settlement
NOTE 1—The vertical strain of the reinforced layer is directly related to
(3). It is necessary to evaluate the resistance to accumulated
the strain in the geocell hoop. Considering a single cell opening, the
permanent deformation of the entire width of the cell wall (or
relationship between the vertical settlement of the infill (or vertical strain,
a representative sample of the entire structural configuration
ε ) and the expansion of the geocell hoop (or hoop strain, ε ) is as follows:
v h
including perforations, if any) in order to characterize its
ε 5 1 1 ε 21 (1)
~ !
v h
long-term behavioral properties.
which results in vertical settlements that are approximately double the
7.1.2.2 The geometry of the individual cells should provide
hoop strain. This concept is especially important for load-bearing appli-
cations where reduction of settlement or vertical strain is of primary sufficient confinement of the infill material. The primary
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geometricattributesthataffectitsabilitytoprovidemechanical 7.1.3.5 Greater Zone of Vertical Influence in the Improved
stability are cell height and the effective diameter of the cell Layer—The zone of influence of the geocell is extended above
opening (13). and below the geocell system where the stabilization mecha-
7.1.3 Design of load support (for example, roads, railways, nism is active. The extent of the zone of influence should be
load platforms) modified by geocells depends on many factors evaluated to quantify its effect on the design.
that should be evaluated through performance testing.
7.1.3.6 Improved Infill Shear Resistance—Improved con-
7.1.3.1 Improved Stiffness—Geocells used directly above a
finementincreasestheshearresistanceofinfillthroughtransfer
weak subgrade/surface primarily provide benefit by improving
of applied vertical loads into geocell hoop stresses.
thestiffness/strengthofthesoilswithinthegeocelllayer,which
7.1.3.7 Reduced Particle Abrasion—Aggregate movement
more widely distributes the applied load, thereby protecting
and particle abrasion are minimized through lateral confine-
soils subject to high deformation levels (14). Geocells used in
ment and the improved lateral support from adjacent cells due
the subbase and base layers primarily improve the modulus of
to the improvement of the infill materials within adjacent cells
the infill material (15). The magnitude of this improvement is
(that is, the slab/mattress effect).
dependent on the properties of the geocell material, its
7.1.4 Optional solutions may include the use of geotextiles
dimensions,thestrengthanddepthoftheinfill,andthestrength
or geogrids together with a geocell to provide enhanced load
of underlying support layers. For all locations, the geocell
support capabilities in areas with expansive soils or very weak
material should maintain its key material properties for signifi-
ground (17).
cantly low levels of accumulated permanent deformation for
7.2 Geocells Used in Retaining Structures, Free-Standing
the entire design life when subjected to the applied design load
Structures, and Fascia Walls:
(see Note 1).
7.2.1 Geocells used in this application are commonly de-
7.1.3.2 Limited Permanent Deformation—Refer to 6.2, 6.8,
ployed on a horizontal surface using two or more layers in
and 6.14.
order to create a stabilized earthen mass or retaining structure.
7.1.3.3 Decreased Vertical Stresses to Lower Layers—
The four general types of earthen structures using geocells are:
Vertical stresses to the subgrade are reduced through incre
...