ASTM D6088-06(2016)

Standard Practice for Installation of Geocomposite Pavement Drains

SIGNIFICANCE AND USE
5.1 This practice is intended to provide installation guidance for designers, specifiers, installation contractors, regulatory agencies, owners, and inspectors who are involved in the planning and installation of geocomposite pavement edgedrains and underdrains. As with any standard practice, modification may be required for specific project conditions or for special local or regional conditions. Fig. 1 shows the proper horizontal alignment of the drain based on various trench conditions outlined in 9.2, and the vertical depth of placement of the drain needed for a geocomposite edge drain to function most effectively as both a collector and conduit.  
Note 1: Drain positioning gate should be located and adjusted to position, and hold the geocomposite drain against the trench wall, to prevent possible “J”ing or “C”ing of the drain during backfilling and compaction.
SCOPE
1.1 This practice covers recommendations and identifies pertinent areas of consideration for the installation of buried geocomposite drains used for highway edgedrains, under-drains, or other pavement drainage applications meeting the requirements of Specification D7001. These recommendations are intended as guidelines for developing a satisfactory construction and installation method to minimize installation-caused deformation or damage and to provide long-term performance of these products. It is also intended as a guideline for ensuring a stable underground environment for these materials under a wide range of service conditions. Because of the numerous and diverse product designs available and the inherent variability of natural ground conditions, achieving satisfactory performance of any one product may require review by the engineer and modification to provisions contained herein to meet specific project requirements.  
1.2 The scope of this practice necessarily excludes product performance criteria such as compressibility in any plane, flow capacity, inlet capacity, or geotextile selection and use. It is, therefore, incumbent upon the product manufacturer, specifier, and project engineer to verify that the product specified for an intended application, when installed according to procedures outlined in this practice, will provide satisfactory long term performance according to criteria established by the owner for that application. A commentary of product performance and installation factors important in achieving a satisfactory installation is included in Appendix X1.  
1.3 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only.  
1.4 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.

General Information

• Status: Historical
• Publication Date: 31-May-2016
• ICS: 93.080.20 - Road construction materials
• Technical Committee: D35 - Geosynthetics
• Drafting Committee: D35.03 - Permeability and Filtration

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: D6088 − 06 (Reapproved 2016)
Standard Practice for
Installation of Geocomposite Pavement Drains
This standard is issued under the fixed designation D6088; 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 2. Referenced Documents
1.1 This practice covers recommendations and identifies 2.1 ASTM Standards:
pertinent areas of consideration for the installation of buried D8 Terminology Relating to Materials for Roads and Pave-
geocomposite drains used for highway edgedrains, under- ments
drains, or other pavement drainage applications meeting the D420 Guide to Site Characterization for Engineering Design
requirements of Specification D7001. These recommendations and Construction Purposes (Withdrawn 2011)
are intended as guidelines for developing a satisfactory con- D653 Terminology Relating to Soil, Rock, and Contained
struction and installation method to minimize installation- Fluids
caused deformation or damage and to provide long-term D698 Test Methods for Laboratory Compaction Character-
performanceoftheseproducts.Itisalsointendedasaguideline istics of Soil Using Standard Effort (12,400 ft-lbf/ft (600
for ensuring a stable underground environment for these kN-m/m ))
materials under a wide range of service conditions. Because of D2321 PracticeforUndergroundInstallationofThermoplas-
the numerous and diverse product designs available and the tic Pipe for Sewers and Other Gravity-Flow Applications
inherent variability of natural ground conditions, achieving D2487 Practice for Classification of Soils for Engineering
satisfactory performance of any one product may require Purposes (Unified Soil Classification System)
review by the engineer and modification to provisions con- D3839 Guide for Underground Installation of “Fiberglass”
tained herein to meet specific project requirements. (Glass-Fiber Reinforced Thermosetting-Resin) Pipe
D4318 Test Methods for Liquid Limit, Plastic Limit, and
1.2 The scope of this practice necessarily excludes product
Plasticity Index of Soils
performance criteria such as compressibility in any plane, flow
D4439 Terminology for Geosynthetics
capacity, inlet capacity, or geotextile selection and use. It is,
D7001 Specification for Geocomposites for Pavement Edge
therefore, incumbent upon the product manufacturer, specifier,
Drains and Other High-Flow Applications
and project engineer to verify that the product specified for an
F412 Terminology Relating to Plastic Piping Systems
intended application, when installed according to procedures
outlined in this practice, will provide satisfactory long term
3. Terminology
performance according to criteria established by the owner for
3.1 Definitions:
that application. A commentary of product performance and
3.1.1 Definitionsusedinthispracticeareinaccordancewith
installation factors important in achieving a satisfactory instal-
Terminologies F412, D8, and D653 unless otherwise indicated.
lation is included in Appendix X1.
3.2 Definitions:
1.3 The values stated in SI units are to be regarded as the
3.2.1 aggregate—a granular material of mineral composi-
standard. The inch-pound units given in parentheses are for
tion such as sand, gravel, shell, slag or crushed stone (see
information only.
Terminology D8).
1.4 This standard does not purport to address all of the
3.2.2 dense-graded aggregate—an aggregate that has a
safety concerns, if any, associated with its use. It is the
particle size distribution such that, when it is compacted, the
responsibility of the user of this standard to establish appro-
resulting voids between the aggregate particles, expressed as a
priate safety and health practices and determine the applica-
percentage of the total space occupied by the material, are
bility of regulatory limitations prior to use.
relatively small.
1 2
This practice is under the jurisdiction of ASTM Committee D35 on Geosyn- For referenced ASTM standards, visit the ASTM website, www.astm.org, or
thetics and is the direct responsibility of Subcommittee D35.03 on Permeability and contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Filtration Standards volume information, refer to the standard’s Document Summary page on
Current edition approved June 1, 2016. Published June 2016. Originally the ASTM website.
approved in 1997. Last previous edition approved in 2011 as D6088 – 06(2011). The last approved version of this historical standard is referenced on
DOI: 10.1520/D6088-06R16. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6088 − 06 (2016)
3.2.3 engineer—the individual in responsible charge of the special local or regional conditions. Fig. 1 shows the proper
work or his duly recognized or authorized representative. horizontal alignment of the drain based on various trench
conditions outlined in 9.2, and the vertical depth of placement
3.2.4 geocomposite, n—a product fabricated from any com-
of the drain needed for a geocomposite edge drain to function
bination of geosynthetics with geotechnical materials or other
most effectively as both a collector and conduit.
synthetics which is used in a geotechnical application.
5.2 Fig. 2 shows the typical type and arrangement of
3.2.5 geosynthetic, n—a planar product manufactured from
equipment used to install geocomposite highway edgedrains.
polymeric material used with foundation, soil, rock, earth, or
The combination of these recommended installation
any other geotechnical engineering related material as an
conditions, techniques, and equipment are critical to the
integral part of a man-made project, structure or system. (See
satisfactory long term performance of these products.
Terminology D4439.)
3.2.6 geotextile, n—any permeable geosynthetic comprised
6. Inspection, Handling, and Storage
solely of textiles. (See Terminology D4439.)
6.1 Inspection—Upon receipt, inspect each shipment of
3.2.7 manufactured aggregates—aggregates such as slag
pipe, geocomposite, and fittings for conformance to product
that are products or byproducts of a manufacturing process, or
specifications and contract documents, and check for damage.
natural aggregates that are reduced to their final form by a
The engineer should reject damaged, deformed, crushed, or
manufacturing process such as crushing.
nonconforming material and remove from the project.
3.3 open-graded aggregate—anaggregatethathasaparticle
6.2 HandlingandStorage—Handleandstorethematerialin
size distribution such that, when it is compacted, the voids
such a way as to prevent damage. Protect all geotextile
between the aggregate particles, expressed as a percentage of
materials from sunlight exposure until immediately before
the total space occupied by the material, remain relatively
installation.
large.
7. Backfill Materials
3.4 optimum moisture content—Themoisturecontentofsoil
7.1 Backfill material selection and placement method
at which its maximum density is obtained (see Test Methods
should be based primarily on achieving adequate compaction
D698).
without damaging the drainage panel, while also achieving
3.5 permeability, n—the rate of flow of a liquid under a
intimate contact with the trench wall or backfill material, or
differential pressure through a material.
both. Excessive compaction efforts may damage geocomposite
3.6 permeability, n—of geotextiles, hydraulic conductivity.
drainage materials and should be avoided. Skid vibratory
–1
compactors that are used in the trench adjacent to the panel,
3.7 permittivity, (γ), (T ), n—geotextiles, the volumetric
can damage the panel if not properly aligned and operated.
flow rate of water per unit cross sectional area per unit head
Free flowing materials, such as pea size crushed stone and dry
under laminar flow conditions, in the normal direction through
or moist sand is suitable in most cases and should be placed in
a geotextile. (See Terminology D4439.)
150 mm (6 in.) lifts. Placement of sand backfill can be done by
3.8 processed aggregates—aggregates that are screened,
flushing or puddling, but this should be used only when
washed, mixed, or blended to produce a specific particle size
approved by the engineer. Post-installation settlement in the
distribution.
backfill will occur if the backfill is not properly densified.
3.9 standard proctor density—themaximumdryunitweight
Significant settlement can cause shoulder drop-off settlement
of soil compacted at optimum moisture content, as obtained by
and other pavement distress problems and structure damage to
laboratory test in accordance with Test Methods D698.
the panels. Permeability of the backfill material must also be
considered; open-graded backfills will promote higher ground
4. Summary of Practice
waterflowtothedrainagesystem,willprovidealargersinkfor
4.1 This practice outlines the key installation criteria that
collecting water, and will also provide additional flow area
should be addressed for proper installation and maximum
during maximum rainfall events. Soil migration from adjacent
performance of geocomposite edge or underdrain materials, or
soils (trench walls) must be considered when using open
both. The engineer should review the specifics of the system.
graded backfills.
Geocomposite drainage materials in this practice are products
7.2 Classification—Materials for potential use as embed-
meeting Specification D7001. Trench excavation, the depth of
ment and backfill of various components of subsurface drain-
drain placement, type of backfill, backfill placement, compac-
age systems are classified in Fig. 3. They include natural,
tion of backfill, product fittings and equipment used during
manufactured, and processed aggregates and the soil types
installation are addressed in this practice.
classified according to Classification D2487. Processed mate-
5. Significance and Use
rials produced for highway construction (including coarse
aggregate, base, subbase, and surface course materials) when
5.1 Thispracticeisintendedtoprovideinstallationguidance
used for embedment and backfill, should be classified in
for designers, specifiers, installation contractors, regulatory
accordance with this section and Fig. 3 according to particle
agencies, owners, and inspectors who are involved in the
size, shape, and gradation.
planning and installation of geocomposite pavement edge-
drains and underdrains. As with any standard practice, modi- 7.3 Installation and Use—Fig.4providesrecommendations
fication may be required for specific project conditions or for on installation and use based on class of soil or aggregates.
D6088 − 06 (2016)
FIG. 1 Typical Type and Arrangement of Drain
7.3.1 Use of Class III Soils and Aggregates—These mate- 7.4.2 Class IB Materials—Class IB materials are processed
rials may be used as recommended in Fig. 4, provided the by mixing Class IA and natural or processed sands to produce
permeability of the material is adequate and approved by the a particle size distribution that minimizes migration from
engineer. adjacent materials that contain fines. They are more densely
7.3.2 Use of Class IVA, Class IVB and Class V Soils and graded than Class IAmaterials and thus require more compac-
Frozen Materials—These materials are not recommended for
tive effort to achieve the minimum density specified. When
backfill and shall be excluded from the final backfill except properly compacted, Class IB materials offer high stiffness and
where approved by the engineer.
strength.ClassIBmaterialsmayberelativelyfreedraining,but
the amount and gradation of fines must be controlled.
7.4 Description of Backfill Material—Sections 7.4.1
7.4.3 Class II Materials—Class II materials provide a
through 7.4.5 describe characteristics of materials recom-
relatively high level of structural support. Open graded groups
mended for backfill. Consideration must be given to the
may allow migration and gradations shall be checked for
potential for migration of fines from adjacent materials into the
compatibility with adjacent material. Typically, Class II mate-
backfill (see appendix).
rials consist of rounded particles and are less stable than
7.4.1 Class IA Materials—Class IAmaterials provide maxi-
angular materials unless they are confined and compacted.
mum stability and support for a given density due to angular
interlockofparticles.Withminimumeffort,thesematerialscan 7.4.4 Class III Materials—Class III materials provide less
be installed in relatively high densities over a wide range of support for a given density than Class I or Class II materials.
moisture contents. The high permeability of Class IAmaterials Higher levels of compactive effort may be required unless
can aid in the performance of these drainage systems. moisture content is carefully controlled. These materials pro-
However, careful consideration must be given to the potential vide satisfactory levels of structural support once proper
for migration of fines from adjacent materials into the open- density is achieved. Fines content should be minimized for
graded Class IA materials. optimum permeability.
D6088 − 06 (2016)
NOTE 1—Drain positioning gate should be located and adjusted to position, and hold the geocomposite drain against the trench wall, to prevent possible “J”ing or “C”ing of the drain during
backfilling and compaction.
FIG. 2 Proper Horizontal Alignment

D6088 − 06 (2016)
NOTE 1—The Attenberg Limits shown in this figure are determined per Test Method D4318.
FIG. 3 Classification of Materials for Potential Use as Embedment and Backfill of Various Components of Subsurface Drainage Systems
7.4.5 Class IVA Materials—Class IVA materials require a limits to permit placement and compaction to required density
geotechnical evaluation prior to use. These materials may not levels with reasonable effort.
be appropriate due to poor permeability or water caused
7.6 Maximum Aggregate Size—To enhance placement
instability, particularly under wheel loads.
around geocomposite drains and to prevent damage to these
7.5 Moisture Content of Embedment Material—The mois- structures,themaximumaggregatesizeshouldbe19mm(0.75
ture content of embedment materials must be within suitable in.).
D6088 − 06 (2016)
FIG. 4 Recommendations for Installation and Use of Soils and Aggregrate for Foundation, Embedment and Backfill
8. Trench Excavation 9. Installation
8.1 Genera
...

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.
Designation: D6088 − 06 (Reapproved 2011) D6088 − 06 (Reapproved 2016)
Standard Practice for
Installation of Geocomposite Pavement Drains
This standard is issued under the fixed designation D6088; 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
1.1 This practice covers recommendations and identifies pertinent areas of consideration for the installation of buried
geocomposite drains used for highway edgedrains, under-drains, or other pavement drainage applications meeting the requirements
of Specification D7001. These recommendations are intended as guidelines for developing a satisfactory construction and
installation method to minimize installation-caused deformation or damage and to provide long-term performance of these
products. It is also intended as a guideline for ensuring a stable underground environment for these materials under a wide range
of service conditions. Because of the numerous and diverse product designs available and the inherent variability of natural ground
conditions, achieving satisfactory performance of any one product may require review by the engineer and modification to
provisions contained herein to meet specific project requirements.
1.2 The scope of this practice necessarily excludes product performance criteria such as compressibility in any plane, flow
capacity, inlet capacity, or geotextile selection and use. It is, therefore, incumbent upon the product manufacturer, specifier, and
project engineer to verify that the product specified for an intended application, when installed according to procedures outlined
in this practice, will provide satisfactory long term performance according to criteria established by the owner for that application.
A commentary of product performance and installation factors important in achieving a satisfactory installation is included in
Appendix X1.
1.3 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for
information only.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
D8 Terminology Relating to Materials for Roads and Pavements
D420 Guide to Site Characterization for Engineering Design and Construction Purposes (Withdrawn 2011)
D653 Terminology Relating to Soil, Rock, and Contained Fluids
3 3
D698 Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort (12,400 ft-lbf/ft (600 kN-m/m ))
D2321 Practice for Underground Installation of Thermoplastic Pipe for Sewers and Other Gravity-Flow Applications
D2487 Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System)
D3839 Guide for Underground Installation of “Fiberglass” (Glass-Fiber Reinforced Thermosetting-Resin) Pipe
D4318 Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils
D4439 Terminology for Geosynthetics
D7001 Specification for Geocomposites for Pavement Edge Drains and Other High-Flow Applications
F412 Terminology Relating to Plastic Piping Systems
3. Terminology
3.1 Definitions:
3.1.1 Definitions used in this practice are in accordance with Terminologies F412, D8, and D653 unless otherwise indicated.
This practice is under the jurisdiction of ASTM Committee D35 on Geosynthetics and is the direct responsibility of Subcommittee D35.03 on Permeability and Filtration
Current edition approved Oct. 1, 2011June 1, 2016. Published NovemberJune 2016. Originally approved in 1997. Last previous edition approved in 20062011 as
D6088D6088 – 06–06.(2011). DOI: 10.1520/D6088-06R11.10.1520/D6088-06R16.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6088 − 06 (2016)
3.2 Definitions:
3.2.1 aggregate—a granular material of mineral composition such as sand, gravel, shell, slag or crushed stone (see Terminology
D8).
3.2.2 dense-graded aggregate—an aggregate that has a particle size distribution such that, when it is compacted, the resulting
voids between the aggregate particles, expressed as a percentage of the total space occupied by the material, are relatively small.
3.2.3 engineer—the individual in responsible charge of the work or his duly recognized or authorized representative.
3.2.4 geocomposite, n—a product fabricated from any combination of geosynthetics with geotechnical materials or other
synthetics which is used in a geotechnical application.
3.2.5 geosynthetic, n—a planar product manufactured from polymeric material used with foundation, soil, rock, earth, or any
other geotechnical engineering related material as an integral part of a man-made project, structure or system. (See Terminology
D4439.)
3.2.6 geotextile, n—any permeable geosynthetic comprised solely of textiles. (See Terminology D4439.)
3.2.7 manufactured aggregates—aggregates such as slag that are products or byproducts of a manufacturing process, or natural
aggregates that are reduced to their final form by a manufacturing process such as crushing.
3.3 open-graded aggregate—an aggregate that has a particle size distribution such that, when it is compacted, the voids between
the aggregate particles, expressed as a percentage of the total space occupied by the material, remain relatively large.
3.4 optimum moisture content—The moisture content of soil at which its maximum density is obtained (see Test Methods
D698).
3.5 permeability, n—the rate of flow of a liquid under a differential pressure through a material.
3.6 permeability, n—of geotextiles, hydraulic conductivity.
–1
3.7 permittivity, (γ), (T ), n—geotextiles, the volumetric flow rate of water per unit cross sectional area per unit head under
laminar flow conditions, in the normal direction through a geotextile. (See Terminology D4439.)
3.8 processed aggregates—aggregates that are screened, washed, mixed, or blended to produce a specific particle size
distribution.
3.9 standard proctor density—the maximum dry unit weight of soil compacted at optimum moisture content, as obtained by
laboratory test in accordance with Test Methods D698.
4. Summary of Practice
4.1 This practice outlines the key installation criteria that should be addressed for proper installation and maximum performance
of geocomposite edge or underdrain materials, or both. The engineer should review the specifics of the system. Geocomposite
drainage materials in this practice are products meeting Specification D7001. Trench excavation, the depth of drain placement, type
of backfill, backfill placement, compaction of backfill, product fittings and equipment used during installation are addressed in this
practice.
5. Significance and Use
5.1 This practice is intended to provide installation guidance for designers, specifiers, installation contractors, regulatory
agencies, owners, and inspectors who are involved in the planning and installation of geocomposite pavement edgedrains and
underdrains. As with any standard practice, modification may be required for specific project conditions or for special local or
regional conditions. Fig. 1 shows the proper horizontal alignment of the drain based on various trench conditions outlined in 9.2,
and the vertical depth of placement of the drain needed for a geocomposite edge drain to function most effectively as both a
collector and conduit.
5.2 Fig. 2 shows the typical type and arrangement of equipment used to install geocomposite highway edgedrains. The
combination of these recommended installation conditions, techniques, and equipment are critical to the satisfactory long term
performance of these products.
6. Inspection, Handling, and Storage
6.1 Inspection—Upon receipt, inspect each shipment of pipe, geocomposite, and fittings for conformance to product
specifications and contract documents, and check for damage. The engineer should reject damaged, deformed, crushed, or
nonconforming material and remove from the project.
6.2 Handling and Storage—Handle and store the material in such a way as to prevent damage. Protect all geotextile materials
from sunlight exposure until immediately before installation.
7. Backfill Materials
7.1 Backfill material selection and placement method should be based primarily on achieving adequate compaction without
damaging the drainage panel, while also achieving intimate contact with the trench wall or backfill material, or both. Excessive
D6088 − 06 (2016)
FIG. 1 Typical Type and Arrangement of Drain
compaction efforts may damage geocomposite drainage materials and should be avoided. Skid vibratory compactors that are used
in the trench adjacent to the panel, can damage the panel if not properly aligned and operated. Free flowing materials, such as pea
size crushed stone and dry or moist sand is suitable in most cases and should be placed in 150 mm (6 in.) lifts. Placement of sand
backfill can be done by flushing or puddling, but this should be used only when approved by the engineer. Post-installation
settlement in the backfill will occur if the backfill is not properly densified. Significant settlement can cause shoulder drop-off
settlement and other pavement distress problems and structure damage to the panels. Permeability of the backfill material must also
be considered; open-graded backfills will promote higher ground water flow to the drainage system, will provide a larger sink for
collecting water, and will also provide additional flow area during maximum rainfall events. Soil migration from adjacent soils
(trench walls) must be considered when using open graded backfills.
7.2 Classification—Materials for potential use as embedment and backfill of various components of subsurface drainage
systems are classified in Fig. 3. They include natural, manufactured, and processed aggregates and the soil types classified
according to Classification D2487. Processed materials produced for highway construction (including coarse aggregate, base,
subbase, and surface course materials) when used for embedment and backfill, should be classified in accordance with this section
and Fig. 3 according to particle size, shape, and gradation.
7.3 Installation and Use—Fig. 4 provides recommendations on installation and use based on class of soil or aggregates.
7.3.1 Use of Class III Soils and Aggregates—These materials may be used as recommended in Fig. 4, provided the permeability
of the material is adequate and approved by the engineer.
7.3.2 Use of Class IVA, Class IVB and Class V Soils and Frozen Materials—These materials are not recommended for backfill
and shall be excluded from the final backfill except where approved by the engineer.
7.4 Description of Backfill Material—Sections 7.4.1 through 7.4.5 describe characteristics of materials recommended for
backfill. Consideration must be given to the potential for migration of fines from adjacent materials into the backfill (see appendix).
D6088 − 06 (2016)
NOTE 1—Drain positioning gate should be located and adjusted to position, and hold the geocomposite drain against the trench wall, to prevent possible “J”ing or “C”ing of the drain during
backfilling and compaction.
FIG. 2 Proper Horizontal Alignment

D6088 − 06 (2016)
NOTE 1—The Attenberg Limits shown in this figure are determined per Test Method D4318.
FIG. 3 Classification of Materials for Potential Use as Embedment and Backfill of Various Components of Subsurface Drainage Systems
7.4.1 Class IA Materials—Class IA materials provide maximum stability and support for a given density due to angular
interlock of particles. With minimum effort, these materials can be installed in relatively high densities over a wide range of
moisture contents. The high permeability of Class IA materials can aid in the performance of these drainage systems. However,
careful consideration must be given to the potential for migration of fines from adjacent materials into the open-graded Class IA
materials.
7.4.2 Class IB Materials—Class IB materials are processed by mixing Class IA and natural or processed sands to produce a
particle size distribution that minimizes migration from adjacent materials that contain fines. They are more densely graded than
Class IA materials and thus require more compactive effort to achieve the minimum density specified. When properly compacted,
Class IB materials offer high stiffness and strength. Class IB materials may be relatively free draining, but the amount and gradation
of fines must be controlled.
D6088 − 06 (2016)
FIG. 4 Recommendations for Installation and Use of Soils and Aggregrate for Foundation, Embedment and Backfill
7.4.3 Class II Materials—Class II materials provide a relatively high level of structural support. Open graded groups may allow
migration and gradations shall be checked for compatibility with adjacent material. Typically, Class II materials consist of rounded
particles and are less stable than angular materials unless they are confined and compacted.
7.4.4 Class III Materials—Class III materials provide less support for a given density than Class I or Class II materials. Higher
levels of compactive effort may be required unless moisture content is carefully controlled. These materials provide satisfactory
levels of structural support once proper density is achieved. Fines content should be minimized for optimum permeability.
7.4.5 Class IVA Materials—Class IVA materials require a geotechnical evaluation prior to use. These materials may not be
appropriate due to poor permeability or water caused instability, particularly under wheel loads.
7.5 Moisture Content
...