usda forest service_geosynthetics for trails in wet areas

8/8/2019 USDA Forest Service_Geosynthetics for Trails in Wet Areas

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United StatesUnited StatesDepartment ofDepartment ofAgricultureAgricultureForest ServiceForest ServiceTechnology &Technology &DevelopmentDevelopmentProgramProgramIn cooperation withIn cooperation withUnited StatesUnited StatesDepartment ofDepartment ofTransportationTransportationFederal HighwayFederal HighwayAdministrationAdministration2300Recreation2300RecreationApril 2008April 200808232813MTDC08232813MTDC

Geosynthetics for

Trails in Wet Areas:2008 Edition

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NITEDS

TATES OF AMER

ICA

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You can order a copy of this document using the order form on the FHWAs

Recreational Trails Program Web site at:http://www.fhwa.dot.gov/environment/rectrails/trailpub.htm

Fill out the order form and either submit it electronically,

fax it to: 3015771421, or mail it to:FHWA R&T Report Center

9701 Philadelphia, Ct, Unit QLanham, MD 20706

Produced by:USDA Forest Service Missoula Technology and Development Center

5785 Hwy. 10 West Missoula, MT 59808-9361

Phone: 4063293978 Fax: 4063293719

E-mail: [email protected]

This document was produced in cooperation with the Recreational Trails Program of the Federal

Highway Administration, U.S. Department of Transportation.

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the

interest of information exchange. The United States Government assumes no liability for its contents or use

thereof.

The contents of this report reflect the views of the contractor, who is responsible for the accuracy of thedata presented herein. The contents do not necessarily reflect the official policy of the U.S. Department of

Transportation.

This report does not constitute a standard, specification, or regulation. The United States Government does

not endorse products or manufacturers. Trade or manufacturers names appear herein only because they areconsidered essential to the object of this document.

U

NITEDS

TATES OF AMER

ICA

DEPAR

TMEN

TOFTRANSPORTAT

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The Forest Service, United States Department of Agriculture (USDA), has developed this information for the guidance of its employees, its

contractors, and its cooperating Federal and State agencies, and is not responsible for the interpretation or use of this information by anyoneexcept its own employees. The use of trade, firm, or corporation names in th is document is for the information and convenience of the reader,

and does not constitute an endorsement by the Department of any product or service to the exclusion of others that may be suitable.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national

origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, geneticinformation, pol itical beliefs, reprisal , or because all or part of an individuals income is derived from any public assistance program. (Not al l

prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information(Braille, large print, audiotape, etc.) should contact USDAs TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of

discrimination, write to USDA, Director, Office of Civil Right s, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410, or call

(800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer.

James Scott GroenierProject Leader

Steve MonluxGeotechnical Engineer, Northern Region (retired)

Brian VachowskiProject Leader, MTDC (retired)

USDA Forest ServiceTechnology and Development ProgramMissoula, MT

7E72A67 FHWA Trail Geosynthetics

April 2008

Geosynthetics forTrails in Wet Areas:2008 Edition


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Contents

Acknowledgments _________________________________________________________________________ ii

Introduction ______________________________________________________________________________ 1

GeosyntheticsGeneral Inormation _________________________________________________________ 2Geotextiles ____________________________________________________________________________ 3

Geonets_______________________________________________________________________________ 4

Geogrids ______________________________________________________________________________ 4

Geocells ______________________________________________________________________________ 5

GeocompositesSheet Drains ____________________________________________________________ 5

Geo-OthersTurf Reinforcement __________________________________________________________ 6

Basic Geosynthetic Design Concepts or Trail Construction in Wet Areas ___________________________ 7

Specifc Design Applications _________________________________________________________________ 8

Geotextile or Geonet_____________________________________________________________________ 9

Geotextile With Encapsulated FreeDraining Rock ____________________________________________ 10

Geogrid With Geotextile or Geonet ________________________________________________________ 11

Sheet Drains Under Tread Fill ____________________________________________________________ 12Sheet Drains or Geonets Used as Drainage Cutoff Walls________________________________________ 13

Geocell With Geotextile and Permeable Tread Material ________________________________________ 14

Geosynthetic Product Inormation __________________________________________________________ 15

Geotextiles ___________________________________________________________________________ 16

Geonets ______________________________________________________________________________ 17

Geogrids _____________________________________________________________________________ 18

Geocells _____________________________________________________________________________ 20

GeocompositesSheet Drains ____________________________________________________________ 19

Geo-OthersTurf Reinforcement _________________________________________________________ 21

Erosion Control _______________________________________________________________________ 21

Identifcation o Unsuitable Tread Fill Material _______________________________________________ 22

Method AField Comparison ____________________________________________________________ 22

Method BLaboratory Test______________________________________________________________ 22

Method CGeotextile Field Test__________________________________________________________ 22

Case Studies _____________________________________________________________________________ 23

Geoblocks for ATV Trails _______________________________________________________________ 23

Geocell for Trail Bridge Approaches _______________________________________________________ 23

Geotextile for Underdrains _______________________________________________________________ 24

Geocell Problems ______________________________________________________________________ 25

Reerences ______________________________________________________________________________ 26

Web Sites _______________________________________________________________________________ 26

Acknowledgments

This report updates Geosynthetics for Trails in Wet Areas: 2000 Edition, by Steve Monlux and Brian Vachowski. Scott

Groenier and Heather Matusiak updated the 2008 edition, and Brian Vachowski helped coordinate the reports review and

prepare it for publication. Others throughout the Forest Service assisted by reviewing the drafts. This document was pro-

duced with cooperative funding from the Recreational Trails Program of the Federal Highway Administration, U.S. De-

partment of Transportation.


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T

Geosyntheticmaterialscanhelpprevent

trailsfromfailinginwetareas.

Themanytypesofgeo

syntheticmaterials

performthreemajorfunctions:

separation,reinforcement,anddrainage.

Thisreportprovidesinformationonthe

differenttypesofgeosynthetic

materials,explainsbasicgeosynthetic

designconcepts,andprovidesdetailed

productspecificationsandprocurement

sources.

Trails in sot, saturated soils present special chal-

lenges or trail managers. Muddy trails cause

problems or livestock and hikers, both o whom

tend to skirt the edges o mud holes. The use along the edge

o the trail increases the area being damaged. Improperly

constructed trails in wet areas lead to erosion, soil compac-

tion, sedimentation, multiple trails where only one is needed,

and unhappy trail users. Traditional trail construction

methods or wet areas include turnpike or puncheon. These

methods have worked well where rock or wood materials are

readily available. However, geosynthetics can increase the

eectiveness o construction methods and oer additional

alternatives.Geosynthetics are synthetic materials (usually made

rom synthetic polymers) used with soil or rock in many

types o construction. Their use has grown signiicantly in

road construction or the past 40 years, and in trail construc-

tion or the past 5 years.

Guidelines on the use o geosynthetics in trail construc-

tion have not been readily available to trail managers. The

inormation presented here applies some roads technology to

trail design and construction in six categories:

General inormation on geosynthetic products Basic geosynthetic design concepts

Speciic design diagrams or trail construction

over wet, saturated soils

A list o product manuacturers and recommend-

ed physical properties

Identiication o unsuitable tread ill materials

Case studies

Introduction


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G(GCLs) and ield-coated geotextiles are used as

luid barriers to impede the low o liquids or

gases.

Erosion ControlThe geosynthetic acts to

reduce soil erosion caused by rainall impact

and surace water runo. For example, tempo-

rary geosynthetic blankets and permanent

lightweight geosynthetic mats are placed over

the otherwise exposed soil surace on slopes.

Geotextile silt ences are used to remove

suspended particles rom sediment-laden

runo. Some erosion control mats are manuac-

tured using biodegradable wood ibers.Geosynthetic materials (igures and ) include geotex-

tiles (construction abrics), geonets, geogrids, and geocom-

posites, such as sheet drains and geocells. All these materials

become a permanent part o the trail, but must be covered

with soil or rock to prevent damage by ultraviolet light.

Geosynthetic erosion control material also has important

uses or slope and bank protection, but this report does not

discuss those uses.

Manuacturers o erosion control geosynthetics are listed

in the Geosynthetic Product Inormation section. Pleasecontact the manuacturers or additional inormation.

Geoblock, Lockgrid, EcoGrid and Grasspave are used or

tur reinorcement and will be discussed. Because all these

products are synthetic, their use in wilderness should be

reviewed and approved beore they are used.

Geosynthetics have numerous uses in civil engineer-

ing. The basic unctions o geosynthetics include:

ReinforcementThe geosynthetic acts as a

reinorcing element in a soil mass or in combi-

nation with the soil to produce a composite that

has improved strength and deormation

properties. For example, geotextiles and

geogrids are used to add tensile strength to a

soil mass when these are vertical or near-

vertical changes in grade (reinorced soil walls).

SeparationThe geosynthetic acts to separate

two layers o soil that have dierent particlesize distributions. For example, geotextiles are

used to prevent road base materials rom

penetrating into sot underlying subgrade soils,

maintaining design thickness and roadway

integrity. Separators also help to prevent ine-

grained subgrade soils rom being pumped into

permeable granular road bases.

DrainageThe geosynthetic acts as a drain to

carry luid lows through less permeable soils.

For example, geotextiles are used to dissipatepore water pressure at the base o roadway

embankments.

FiltrationThe geosynthetic acts like a sand

ilter by allowing water to move through the

soil while retaining the soil particles. For

example, geotextiles are used to prevent soils

rom migrating into drainage aggregate or pipes

while maintaining low through the system.

Geotextiles are also used below riprap and

other armor materials in coastal and riverbank

protection systems to prevent soil erosion.

ContainmentThe geosynthetic acts as a

relatively impermeable barrier to luids or

gases. For example, geomembranes, thin ilm

geotextile composites, geosynthetic clay liners

GeosyntheticsGeneral Information


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GeotextilesGeotextiles (igure ) are the most widely used geosyn-

thetic. Geotextiles are oten called construction abrics. They

are constructed rom long-lasting synthetic ibers that orm a

abric held together by weaving, heat bonding, or other

means. Geotextiles are primarily used or separation and

reinorcement over wet, unstable soils. They have the ability

to support loads through tensile strength and can allow water,

but not soil, to seep through. They can also be used in

drainage applications where water low is much greater than

normal or wet areas. The physical requirements listed or all

geotextiles in the Geosynthetic Product Inormation

section are stringent enough that the products will work or

properly designed high-low drainage applications.

Figure 2Trail fill material with geotextile. The geotextile layer enhancesthe trail performance by providing separation, reinforcement, and drain-age.

Figure 1Trail fill material without geotextile. The aggregate will losestrength as the f ill material mixes with the subbase.

Figure 3Geotextiles are made from woven and nonwoven fabrics.Felt-like products are easier to work with than slick products that are heat

bonded, woven, or made from slit film. Felt-like products are easier to cutand their flexibility makes them easier to place on curved tra il sections.

Ground surface

Drainage Drainage

Separation

Aggregatecap

Geotextilelayer

Substandard soil base

Trail Fill With Geotextile

Cross contaminationleads to impacts fromshear stress.

Aggregatemigration

Upwardmovementof soil

Aggregatecap

Shear force

Substandardsoil base

Trail Fill Without Geotextile

Ground surface


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GeogridsGeogrids (igure 5) are made rom polyethylene sheeting

that is ormed into very open gridlike conigurations.

Geogrids are good or reinorcement because they have high

tensile strengths and because coarse aggregate can interlock

into the grid structure.

GeonetsGeonets or geonet composites (igure 4) have a thin

polyethylene drainage core that is covered on both sides by

geotextile. Geonets are primarily used or drainage, but also

may unction as separation and reinorcement. Because

geonets have a core plus two layers o geotextile, they

provide more reinorcement than a single layer o geotextile.

Figure 5Geogrids are normally placed on top of a layer of geotextile forseparation from saturated soils in wet areas.

Figure 4Geonets with the two layers of geotextile shown are considereda geocompositethe core of geonet allows drainage to the sides that isnormally adequate for the seepage found under trails in wet areas. Thegeotextile provides reinforcement and separation.


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GeocompositesSheet DrainsSheet drains (igure 7) are a orm o geocomposite

material made with a drainage core and one or two layers o

geotextile. The core o a sheet drain usually is made o a

polyethylene sheet ormed into the shape o an egg crate. The

core provides an impermeable barrier unless it has been

perorated by the manuacturer. Perorated cores are always

covered with geotextile on both sides to prevent soil rom

clogging the drainage passages. Geotextile is bonded to one

or both sides o the core to provide iltration and separation.

When sheet drains are used under trail tread material, they

provide separation, reinorcement, and drainage. Because

sheet drains have greater bending strength than geotextiles or

geonets, less tread ill may be needed above them. Sheet

drains also can be installed vertically in covered trenches

beside the trail to drain o subsurace water.

GeocellsGeocells (igure 6) are usually made rom polyethylene

strips 50 to 00 millimeters ( to 8 inches) high that have

been bonded to orm a honeycomb. The product is shipped

collapsed so it is more compact. During installation, the

material is pulled open and the honeycomb structure is

staked to the ground surace. Each o the cells is illed and

compacted. Compacting trail tread material within the cell

increases the strength o the layer and reduces settlement into

sot, saturated soils. Geocells are good or reinorcement and

reduce the amount o ill material required.

Figure 7Geocomposites such as sheet drains have a large cross sectionthat allows drainage. If geotextiles are placed under the trail tread, thesheet drain should be oriented with the geotextile on the bottom and the

plastic core on top. This orientation reduces the amount of fill needed.

Figure 6Geocell usually has geotextile under it for separation from wet,saturated soil. Normally, the cells are filled with a soil that drains well.


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Geo-OthersTurf Reinforcement

Other proprietary products used or reinorcement are

considered geo-others. Typically, they are manuactured

rom recycled plastics to protect tur rom rutting, erosion,

and soil compaction. Geo-other products include Geoblock

(igure 8), Lockgrid, EcoGrid, and Grasspave (igure 9).

The MTDC report Managing Degraded O-Highway

Vehicle Trails in Wet, Unstable, and Sensitive Areas (Meyer

00) has inormation on tur reinorcement materials and

their installation.

Figure 8Geoblock, a very stiff material, is one of the many products for turf reinforcement.

Figure 9Grasspave2 is another product for turf reinforcement.


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TTrails in wet areas oten are unstable because they are

saturated by subsurace moisture and precipitation.

Geosynthetics help create stable trail suraces by

providing:

SeparationGeotextiles, geonets, and

geocomposites (sheet drains) keep saturated,

weak native soils rom contaminating stronger,

load-bearing trail surace materials. These

materials allow water, but not soil, to pass

through them.

DrainageGeotextiles, geonets, and geocom-

posites (sheet drains) improve subsurace

drainage to avoid saturation and weakening othe trail tread.

Reinforcement and Load DistributionAll

geosynthetics provide some degree o tread

reinorcement and load distribution. This may

decrease the amount o imported ill material

needed or trail suracing.

Geosynthetics are relatively simple to use. Products that

meet the physical requirements discussed in the Geosyn-

thetic Product Inormation section are tough enough to be

placed over small stumps that stick up rom the groundsurace ater brush has been cleared or trail construction.

Cutting stumps and brush to within a ew inches o the

ground usually is all that is necessary. Normally, joints in

geotextiles, geonets, or geogrids should overlap at least 00

millimeters ( inches). Sometimes sections o material are

joined with pins or clips rather than being overlapped. All

geosynthetics must be stored in their shipping wrappers until

installation because they will deteriorate gradually when

exposed to ultraviolet light.

Selecting good material or tread ill is very important.

Organic, silt, or clay soils should not be used as tread ill

because they become muddy when wet. Use irm mineral

soil, coarse-grained soils, granular material, or small well-

graded angular rock instead. Soil rom wet areas is normally

not suitable or use as tread ill. Unsuitable organic soils are

easily identiied by a dark color and musty odor when damp.

Many soils containing clays and silts are just as unstable, butsuch soils are more diicult to identiy. The Identiication

o Unsuitable Tread Fill Material section discusses several

methods or identiying unsuitable soils.

The amount o acceptable tread ill material you need

over the geosynthetic depends on several site-speciic actors

(table ).

In addition to the applications illustrated in the Speciic

Design Applications section, other combinations o geosyn-

thetic materials are possible and perhaps preerable, depend-

ing on conditions at the site and the native building materialsavailable there. Once you understand the unction o the

dierent types o geosynthetics and product capabilities, you

may be able to identiy many other applications.

Table Factors aecting the recommended thickness o tread ill material over the geosynthetic material.

Factors Affecting Recommended Maximum Thickness Minimum ThicknessTread Thickness Needed Needed

Trail fll quality Mineral soil with little rock, Granular, ree-draining materials

less than 0% silt or clay

Trail tread surace Horse or motorcycle Foot trafc

Tread surace moisture Moisture content predominantly Moisture content predominantly

content during trafc high low

Amount o oundation settlement Continuously wet areas Intermittent sot, wet areas less

more than eet deep than eet deep

Geosynthetic alternative selected Single layer o geotextile Geotextile with other

geosynthetics such as geocells

Trail surace crown maintenance Less than annual Annual

Basic Geosynthetic Design Concepts for TrailConstruction in Wet Areas


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o saturation, and weight o tread ill used. Less tread ill can

be used over geosynthetic products that are rigid or have high

bending strengths because the weight o ill is distributed

over a larger area. Settlement decreases when less ill is

needed to obtain a stable tread surace. For example, much

more tread ill is required or a single layer o geotextile

(igure 0), than or geocell with geotextile (igure ). In this

example, the cost o importing tread ill must be compared to

the increased cost o the geocell.

All alternatives that use tread ill should have a crowned

or outsloped surace to help shed water quickly, improve

stability, and control erosion and sediment production.

Additional tread ill may be needed to rebuild the crownater the trail settles initially. More imported ill will be

needed to maintain the crown i tread wear is high. Alterna-

tives are compared in table .

MMost o the applications shown can be integrated

into standard trail turnpike construction specii-

cations. To simpliy the il lustrations, not all the

components o a complete turnpike (ditches, curb rocks, or

logs, etc.) are shown. Curb logs or rocks may be needed to

conine tread ill unless the ill materials are quite granular.

Shoulders must be maintained to keep geosynthetics covered

to protect them rom ultraviolet light and traic abrasion.

The igures are simpliied cutaway cross-sectional views o

the trail. They normally look much better on paper than they

do during construction.

Geosynthetics usually are placed directly on the ground

without excavation. Many o the illustrations show thevarious applications with a sag in the native soil surace

along the center o the trail alignment. This sag is caused by

adding the weight o the tread ill. The actual amount o

settlement is very site speciic and depends on soil type, level

Figure 10Typical placement of geotextile or geonet through flat, boggy areas.

Figure 11Geocell with geotextile and permeable tread material.

Direction of travel

Tread fill material

Geotextile or geonet

Direction of travel

Permeable tread material

Optional geotextile layer under geocell Geocell

Specific Design Applications


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Geotextile or GeonetSingle-layer geotextile or geonet (see figure 10) separates

fill material from saturated soils and distributes fill weight so

less settling takes place. Because geonets cost more, use them

only where drainage and subsurface moisture conditions are

worst. Avoid using organic, silt, or clay soils for trail tread

material because little subsurface drainage will occur and the

trail tread will become muddy in wet weather. Rocky soils or

crushed aggregate should be used as a tread material i

possible. These materials retain much o their strength when

saturated. Excess surace moisture can drain o through

these permeable materials i the trail is located on a grade or

side slope.

Construction Objectives Geosynthetic Applications

Sheet Sheet

Geogrid Geogrid drain drain Geocell

Geotextile Geonet Geotextile with with with with with

only only sausage3 geotextile geonet geotextile4 geotextile5 geotextile6

Separation (keep tread fill B B A B B B NA. A

separate from poor soils)

Reinforcement (turnpike over D D A B A B NA. A

deep layer of very weak soil)

Reduce quantity of imported D D B B A B C B

fill material

Eliminate trail side ditching D C A C C B D B

Ease of product placement A B C C C B D C

Cost for geosynthetics $ $$ $ $$ $$$ $$$ $$$ $$$$

Weight of geosynthetics:

kilograms per square meter 0.14 0.89 0.28 0.32 1.07 2.3 2.3 1.9

pounds per square yard 0.25 1.64 0.50 0.60 1.98 4.25 4.25 3.45

Alternative Rating Code: A=Best alternative; B=Better than most; C=Not as good as most; D=Least eective; NA=Not applicable;

$ Least expensive => $$$$ Most expensive

1Single layer o geotextile.

2Single layer o geonet.

3Geotextile with encapsulated ree-draining rock. Rock can be large, single-size cobbles, down to relatively clean sands.

4Sheet drains under tread ill.

5Sheet drains or geonets or drainage cuto wall. Extensive ditching required.

6Geocell with geotextile and permeable tread. Granular ill material required; weights are based on 00-mm-deep cells.

Table 2Comparisons of alternative geosynthetic applications.


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Geotextile With EncapsulatedFreeDraining Rock

In the sausage technique (igure ), the geotextile

provides separation rom the saturated soil, and the rock

provides drainage or excess water. Twenty-ive-millimeter

(-inch) lexible plastic pipe outlets or subsurace water may

be desirable where trails are constructed on very lat terrain

to avoid the bath tub eect. I the trail has grade or is built

on a sideslope, other drainage options exist. The rock may be

single-size material rom pea gravel size to cobbles (75 to

00 millimeters or to inches), or it may be a mixture o

rock materials that does not contain silt or clay. The rock can

be just one layer thick i drainage is all that is needed. For

reinorcement, at least 75 millimeters ( inches) o rock

would be recommended. The geotextile is wrapped over the

rock layer with a 00-millimeter (-inch) overlap to ensure

encapsulation, because settlement o saturated soil can pull

the overlap apart.

Figure 12The encapsulation or sausage technique, with native rock used for drainage.

Free-draining rock

Geotextile (300 millimeters

[12 inches] overlap at center)

Tread fill material

Direction of travel


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Geogrid With Geotextileor Geonet

Figure shows geogrid placed on top o the geotextile

or geonet to add bending strength to the system, decrease

settling, and reduce the amount o ill material required.

Very little drainage is required with this design, unless

geonets are used or the tread material is permeable (rocky

soils or crushed aggregate). The geogrid should be pulled

taut to remove wrinkles beore staking. The stakes and poles

provide some pretension o the geogrid, better using its

strength. The geotextile or geonet provides separation rom

the saturated soil and keeps the drainage paths along the

bottom o the ill material rom clogging. See Section 964 o

the Standard Speciications or Construction and Mainte-

nance o Trails (996) or additional inormation.

Figure 13Geogrid with geotextile or geonet.

Direction of travel

Pole restsagainst stakes

Geogrid

Geotextile or geonet

Fill material, permeable soil,

or aggregate preferred


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Sheet Drains Under Tread FillSheet drains under tread ill (igure 4) provide separa-

tion rom saturated soils and distribute the weight o the trail

tread to limit settling. Install the product with the plastic core

side acing up and the abric side acing down. This orienta-

tion takes advantage o the plastic cores compressive

strength and the abrics tensile strength, reducing the

amount o settling and the amount o tread ill required.

Twenty-ive-millimeter- (-inch-) diameter lexible plastic

pipe can be used as a drainage outlet to take ull advantage

o the sheet drains capabilities. I the trail is on a grade or

side slope, an outlet pipe or daylight section could provide

drainage.

Figure 14A sheet drain under fill material.

Geotextile

Sheet drain

Any type of fill material

(100 millimeters or 4 inchesminimum thickness)

Direction of travel


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Sheet Drains or Geonets Usedas Drainage Cutoff Walls

I a section o trail is on a side slope where subsurace

water saturates the uphill side, a cuto wall can be construct-

ed to intercept surace and subsurace moisture (igure 5),

helping drain and stabilize the trail section. This application

is especially beneicial where the cut slope sloughs continu-

ally, illing ditches. The sheet drain or geonet should be

installed within meter ( eet) o the trails edge. The

proper depth o the collection pipe and location o the sheet

drain can be determined by probing the saturated soil with a

short length o Number 4 reinorcing steel (rebar). Collector

and outlet pipes can be made rom lexible plastic pipe. Keep

the top edge o the drain above the ground to capture surace

runo moving down the slope. Cover the exposed material

with large rocks to protect the mater ial rom ultraviolet light.

The collector pipe can be drained into an outlet pipe or with

a sheet drain or geonet panel installed under the trail. This

application requires ditching to intercept and drain water.

Ditching is normally more extensive on latter terrain.

Figure 15A sheet drain or geonet used to intercept seepage.

Fill material

Direction of travel Large

rocks

Timber

Collectorpipe

Sheet drain or geonet.

Geotextile side facesuphill to intercept

seepage.Outlet pipe orsheet drain

Seepage


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Geocell With Geotextile andPermeable Tread Material

Geocell provides coninement chambers that distribute

the trail tread loads over a wider area and reduce settling (see

igure ). Geocell works best in sandy soils, rocky soils,

crushed aggregate, or ree-draining rock, where it increases

the treads load-bearing capacity and prevents eet and

hooves rom punching holes into the trail. The geotextile

provides separation between saturated soil and the tread ill

material. Less tread ill will be needed with geotextile

because settling is reduced. There is no subsurace drainage

i the trail is on lat ground. I the trail has a grade or is built

on a side slope, moisture will drain through the permeable

tread ill. Organic, silt, and clay soils are not desirable as ill

or geocells because these soils will probably remain

saturated and unstable, meaning they will not be strong

enough to carry the loads on the trail. Geocell does not

increase the load-bearing strength o clay or silt.


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15

TThe ollowing manuacturers and products were

included in the Speci iers Guide or Geosynthetic

Materials published by Geosynthetics Magazine,

available rom the Industrial Fabric Association International

Resource Center, 80 County Road B.W., Roseville, MN

55406 (800544). The recommended minimum

physical properties listed are rom the Forest Services

Standard Speciications or Construction and Maintenance

o Trails (996). The recommended physical properties are

typically on the low end o those available because trails

applications are much less demanding than geosynthetic

applications in road construction where heavy machinery and

large, angular boulders require stronger products.This edition o Geosynthetics or Trails in Wet Areas

does not recommend speciic products. Hundreds o suitable

products are available rom manuacturers and even home

improvement centers. Most manuacturers and geotechnical

or materials engineers can help you select products i you

provide details on soil and moisture conditions and expected

loads (trails generally have light loads).

No prices are listed. Prices may change quickly because

o changes in the price o the petroleum (the raw material).

Call the listed phone numbers or current prices delivered to

your area or to contact the local sales representative. Manu-

acturers may provide prices by the square meter, square

yard, square oot, or or ull rolls. Unit costs decrease as the

amount ordered increases. All geosynthetic products can be

cut in the ield or cut by the manuacturer to meet yourrequirements.

Geosynthetic Product Information


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16

Geotextiles

Critical physical properties or geotextiles used in trail

construction:

Material structure: Nonwoven

Polymer composition: Polypropylene

Apparent opening by ASTM D 47587: Less than

0.97 millimeter (mesh larger than No. 50)

Permittivity by ASTM D4499: More than 4,060

liters per minute per square meter (more than 00gallons per minute per square oot)

Puncture strength by ASTM D4888: More than

0.0 kilonewton (more than 5 pounds)

Mullen burst by ASTM D 78687: More than 900

kilopascals (more than 0 pounds per square inch)

Trapezoid tear strength by ASTM D459: More

than 0.0 kilonewton (more than 5 pounds)

Grab tensile at 50 percent elongation by ASTM

D469: More than 0.55 kilonewton (more than

80 pounds)

Ultraviolet degradation: More than 70 percent

retained strength at 50 hours

Notes: The products that work best or trail applications

typically are the nonwoven, elt-like materials that are easierto work with rather than heat-bonded or slit-ilm products

that have a slick surace. Physical property requirements are

minimum average roll values where applicable. Compare

your desired widths with standard roll widths and consult

with manuacturers when deciding whether its best to cut the

abric in the ield or have the manuacturer cut it.

Manufacturer or Company Phone Number Web Site

Belton Industries Inc. 800845875 www.beltonindustries.com

Carthage Mills 80054440 www.carthagemills.com

Contech Earth Stabilization Solutions Inc. 8665585 www.contechess.com

Dalco Nonwovens 88459577 www.dalcononwovens.com

Fiberweb PLC 80067 www.iberweb.com

GSE Lining Technology Inc. 80045008 www.gseworld.com

Huesker Inc. 80094948 www.huesker.com

LINQ Industrial Fabrics Inc. 8004454675 www.linq.com

Maccaerri Inc. 800687744 www.maccaerri-usa.com

Mirai (TenCate Geosynthetics) 8006859990 www.mirai.com

Propex Inc. 80067 www.geotextile.com

SKAPS Industries 70669440 www.skaps.com

TNS Advanced Technologies by Maple Textile 80086758 www.mapletextile.com

Vantage Partners LLC 704878700

WEBTEC Inc. LLC 80048007 www.webtecgeos.com

Typical Product Unit Weight: 0. kilogram per square meter (0.5 pound per square yard)


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17

Geonets

Critical physical properties o geonets used in trail

construction:

Polymer composition o core (net or mesh):

Medium- or high-density polyethylene.

Geotextile: Must be attached to both sides o

the core and meet or exceed the requirements o

AASHTO M 88 Subsurace Drainage Class Bwith permeability greater than 0.000 centime-

ter per second, and an apparent opening size

less than 0.97 millimeter (larger than the No.

50 U.S. Standard Sieve).

Core thickness: Thicker than 5 millimeters by

ASTM D599.

Compressive strength o core: Stronger than

500 kilopascals by ASTM D6.

Transmissivity with gradient o 0. and pressure

o 0 kilopascals: More than 0.0009 square

meter per second (more than 4 gallons perminute per oot).

Notes: Discuss the roll width and length requirements

or your project with manuacturers.


Agru America Inc. 8007478 www.agruamerica.com

CETCO Lining Technologies 800579948 www.cetco.com

Fiberweb PLC 80067 www.iberweb.com


Poly-Flex Inc. 888765959 www.poly-lex.com

Rainy Day Water Inc. 80975895 www.rainydaywater.com

SKAPS Industries 70669440 www.skaps.com

Tenax Corp. 800568495 www.tenaxus.com

Typical product unit weight: 0.89 kilogram per square meter (.64 pounds per square yard)


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18

Geogrids

Critical physical properties o geogrids used or trail

applications:

Polymer type: High-density polyethylene,

polypropylene, or polyester with acrylic or PVC

coating

Mass per unit area by ASTM D569: 75

grams per square meter (more than 5.5 ounces

per square yard)

Maximum aperture size: Machine direction

(MD): 00 millimeters (4 inches). Cross

direction (XD): 75 millimeters ( inches)

Wide-width strip tensile strength at 5-percent

strain by ASTM D4595-86: Machine direction

(MD): 8 kilonewtons per meter (550 pounds per

oot). Cross direction (XD): 6 kilonewtons per

meter (40 pounds per oot)

Notes: Speciy desired product widths and lengths or

the project application.



Colbond Inc. 8006579 www.enkamat.com


Huesker Inc. 80094948 www.huesker.com

Linear Composites Limited 4987678 www.linearcomposites.com



Strata Systems Inc. 8006807750 www.geogrid.com

Synteen Technical Fabrics 80079686 www.synteen.com


Tensar International Corp. 8888677 www.tensar-international.com


Typical product unit weight: .75 kilograms per square meter (0.4 pound per square yard).


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19

Geocells

Critical physical properties o geocells used or trail

construction:

Composition: Polyethylene or high-density

polyethylene.

Geocell weight expanded: Heavier than .7

kilograms per square meter (heavier than 50

ounces per square yard).

Minimum cell seam peel strength by U.S.

Army Corps o Engineers Technical Report G:

869, Appendix A: 800 newtons (80 pounds).

Expanded dimensional properties: As speciied

by the designersee the manuacturers

dimensions.

Notes: Speciy the desired product widths or the project

application. The 00-millimeter (4-inch) cell depth should be

adequate or trailsdepths rom 50 to 00 millimeters ( to

8 inches) are available. Consult manuacturers or the

availability o dierent section widths and alteration o

standard section widths to it your project needs.



Geo Products LLC/Envirogrid 80044474 www.geoproducts.org

Jobsite Products Inc. 800984900 www.jobsiteproducts.com

Layield Plastics Inc. 8007966868 www.layieldgroup.com


Presto Products Co. 80054844 www.prestogeo.com



Typical product unit weight: .55 kilograms per square meter (.9 pounds per square yard)


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20

GeocompositesSheet Drains

Critical physical properties o sheet drains or trail

construction:

Structure: Single- or double-dimpled core

Core polymer composition: Polystyrene or

polypropylene

Attached geotextile: Nonwoven on one side i

the core is solid, on both sides i the core is

perorated. Geotextile must meet or exceed the

requirements o AASHTO M 88 Subsurace

Drainage Class B with permeability more than

0.000 centimeter per second and an apparent

opening size less than 0.97 millimeter (larger

than the No. 50 U.S. Standard Sieve)

Core thickness by ASTM D599: Thicker than

0 millimeters (thicker than 0.40 inch)

Core compressive strength at yield by ASTM

D6: More than 650 kilopascals (more than

95 pounds per square inch)

Notes: Compare desired width with standard sheet width

and consult with manuacturers to learn whether the material

can be cut easily in the ield and how much it would cost to

have it cut at the actory. Sheet drains with cores made rom

thicker materials usually have greater bending strength,

limiting the amount o settling in sot soils and reducing the

amount o ill material needed. Various core thicknesses are

available.


American Wick Drain Corp. 8004945 www.americanwick.com



Drainage Products Inc. 860668508 www.drainaway.com

Fiberweb, PLC 80067 www.iberweb.com


JDR Enterprises Inc. 800847569 www.j-drain.com

LINQ Industrial Fabrics Inc. 8004454675 www.linq.com


TNS Advanced Technologies by Maple Textile 80086758 www.mapletextile.com


Typical product unit weight: . kilograms per square meter (4.5 pounds per square yard).


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21

Geo-OthersTurf Reinforcement

Erosion Control



Geo Products LLC/Envirogrid 80044474 www.geoproducts.org

American Excelsior Co. 8007777645 www.curlex.com

Belton Industries Inc. 800845875 www.beltonindustries.com




East Coast Erosion Blankets 800584005 www.erosionblankets.com

Fiberweb, PLC 80067 www.iberweb.com

Geo Products LLC/Envriogrid 80044474 www.geoproducts.org


Mirai (TenCate Geosythetics) 8006859990 www.mirai.com

North American Green 80077040 www.nagreen.com

Presto Products Co. 80054844 www.prestogeo.com

Proile Products LLC 800508868 www.proileproducts.com

Propex Inc. 80067 www.geotextile.com

SRW Products 8007596 www.srwproducts.com


Vantage Partners LLC 704878700

Watersaver Co. Inc. 8005544 www.watersaver.com

Western Excelsior Corp. 8008857 www.westernexcelsior.com

Manufacturer or Company Product Phone Number Web Site

Invisible Structures Inc. Grasspave 80050 www.invisiblestructures.com

Norleans Technologies Inc. Lockgrid 6849 www.norleanstech.com

Presto Products Co. Geoblock 80054844 www.prestogeo.com

TerraFirm Enterprises EcoGrid 86694757 www.terrairmenterprises.com


26/31

22

SSoils rom wet areas are normally not suitable or use

as tread ill because they are too moisture sensitive

and lose strength easily when they become wet. Its

important to avoid spending scarce dollars to excavate and

haul ill that will ail when wet. Poor materials can be

identiied by several methods.

Organic Soils: Identiied by musty odor when they are

damp, and they are dark in color.

Other Unsuitable Tread Fill Materials: The stability

o tread ill material is inluenced primarily by the amount

o silt or clay. I the ill is more than 0 percent silt and clay,

the ill will probably become unstable when wet. Rough

evaluations or suitability can be done by the ollowingmethods.

Method AField ComparisonCompare proportions o gravel, sand, and ines in

existing trail tread materials with the proportions in borrow

sources. Individual ine-size material particles are not

visible to the naked eye and are classiied as silt or clay. Ithe proportions o gravel, sand, and ines are similar, you can

expect the borrow materials to perorm as well as the

existing trail tread materials. I the borrow source has a

lower proportion o ines, you can expect better perormance.

Method BLaboratory TestTake a 5-kilogram (0-pound) sample o the proposed

tread ill material to a materials testing laboratory or a

washed sieve analysis to determine the percentage o minus

No. 00 material. The minus No. 00 material represents the

amount o silt or clay. I the sample has more than 0 percent

minus No. 00 material, it is not suitable or ill. A washed

sieve analysis typically costs $50 to $00.

Method CGeotextile Field TestBuild a short section o a small-scale trail over a wet

area with a -meter (6-oot) square piece o geotextile and

the proposed tread ill material. The depth o tread ill

should be at least 50 millimeters (6 inches). Saturate the

section with as much water as would be expected under the

worst conditions. Evaluate the stability o the tread material

by stepping onto the tread repeatedly, mimicking traic.

Identification of Unsuitable Tread Fill Material


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23

TThe ollowing case studies show how geosynthetic

materials were used to solve problems on trails. One

o the studies points out problems that can ar ise i

geosynthetic materials are installed improperly.

Geoblocks for ATV TrailsThe Francis Marion National Forest in South Carolina had

serious erosion problems on all-terrain vehicle (ATV) t rails.

The ATVs were causing ruts. Water collecting in the ruts

compounded the problem (figure 16). The forest reinforced thetrail with Geoblocks, solving the problem (figure 17). Other

national forests and national parks now use turf reinforcement

products to reduce erosion and reinforce ATV trails.

Geocells for Trail BridgeApproaches

The Tongass National Forest in Alaska is using geocells

to build approaches or trail bridges (igure 8). In the past,

approaches have sloughed o because o the steep embank-

ments and wet conditions there. The geocells have worked

wonders and are highly recommended or trail bridge

approaches in the Tongass (igure 9).

Figure 16An ATV trail in South Carolina before Geoblocks wereinstalled.

Figure 18Using geocells to construct a trail bridge approach.

Figure 17The finished trail after Geoblocks were installed in the FrancisMarion National Forest.

Figure 19A finished trail bridge approach in the Tongass NationalForest.

Case Studies


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29/31

25

Geocell ProblemsTrail maintainers had the right idea when they decided

to install geocells at the approaches to this bridge (igure ).

The geocells would provide a stable approach to the bridge

and keep the ill material rom soughing. Unortunately, they

did not install the geocells deep enough to allow to inches

o gravel cover above them. The geocells were exposed to

traic and gradually unraveled, creating an unsightly and

unsae approach.

Figure 23Geocells placed too close to the surface may unravel. The top of the geocell should be 2 to 3 inches below the surface of compactedtread fill.


30/31

26

Bathurst, R.J. [no date]. Geosynthetics classiication.

International Geosynthetics Society. Available electronically

at: http://geosyntheticssociety.org/source_documents/

Classification.pdf.

Bathurst, R.J. [no date]. Geosynthetics unctions. Interna-

tional Geosynthetics Society. Available electronically at:

http://geosyntheticssociety.org/source_documents/Func-

tions.pdf.

Geosynthetic Materials Association (GMA). 00. Handbook

o geosynthetic materials. Roseville, MN: Geosynthetic

Materials Association. Available electronically at: http://www.gmanow.com/pdf/GMAHandbook_v002.pdf

Industrial Fabrics Association International. 008. Geosyn-

thetics speciiers guide: 008. Roseville, MN: Industrial

Fabrics Association International.

Koerner, Robert M. 005. Designing with geosynthetics, 5th

ed. Upper Saddle River, NJ: Pearson/Prentice Hall.

McKean, J.; Inouye, K. 000. Field evaluation o the long-term perormance o geocomposite sheet drains. Tech. Rep.

0077804SDTDC. San Dimas, CA: U.S. Department o

Agriculture Forest Service, San Dimas Technology and

Development Center. p.

Meyer, Kevin G. 00. Managing degraded o-highway

vehicle trails in wet, unstable, and sensitive environments.

Tech. Rep. 08MTDC. Missoula, MT: U.S. Depart-

ment o Agriculture Forest Service, Missoula Technology

and Development Center. 48 p.

Monlux, Steve; Vachowski, Brian. 000. Geosynthetics or

trails in wet areas: 000 edition. Tech. Rep. 0088

MTDC. Missoula, MT: U.S. Department o Agriculture

Forest Service, Missoula Technology and Development

Center. 8 p.

Shukla, Sanjay K.; Yin Jian-Hua. 006. Fundamentals ogeosynthetic engineering. London, UK: Taylor & Francis

Group. 40 p.

U.S. Army Corps o Engineers. Engineering use o geosyn-

thetics. 995. Available electronically at: http://www.army.

mil/usapa/eng/DR_pubs/dr_a/pdf/tm5_818_8.pdf

U.S. Department o Agriculture Forest Service. 996.

Standard speciications or construction and maintenance o

trails. Eng. Man. EM7700. Washington, DC: U.S.Department o Agriculture Forest Service.

Geosynthetic Institute

http://www.geosynthetic-institute.org/

Geosynthetic Materials Association

http://www.gmanow.com/

Industrial Fabrics Association International

http://www.ifai.com/

International Geosynthetics Society

http://www.geosyntheticssociety.org/guideance.htm

References

Web Sites


31/31

About the Authors

James Scott Groenier, professional engineer, began working for MTDC as a project leader in 2003. Scott earned

a bachelors degree in civil and environmental engineer ing from the University of Wisconsin at Madison and a masters

degree in civil engineering from Montana State University. He worked for the Wisconsin and Illinois State Departments of

Transportation and with an engineering consulting firm before joining the Forest Service in 1992. He worked as the east

zone structural engineer for the Eastern Region and as a civil engineer for the Ashley and Tongass National Forests before

coming to MTDC.Stephen Monlux is an engineering consultant in materials and pavement engineering, contract administration, and

technology transfer for several federal agencies, state Local Technical Assistance Program centers, and numerous counties in

the Northwest. He was the Northern Region materials engineer for the Forest Service in Missoula, MT, for 26 years.

Brian Vachowski was a project and program leader at the MTDC from 1993 until his retirement in 2008. He received

a bachelors degree in forestry from the University of Massachusetts and a masters degree in outdoor recreation from Utah

State University. He has worked for the Nez Perce, Bighorn, Winema, and Routt National Forests.

Library Card

Groenier, James Scott; Monlux, Stephen; Vachowski, Brian. Geosynthetics for trails in wet areas: 2008 edition. Tech.Rep. 08232813MTDC. Missoula, MT: U.S. Department of Agriculture Forest Service, Missoula Technology and Develop-

ment Center. 26 p.

This report updates Geosynthetics for Trails in Wet Areas: 2000 Edition, by Steve Monlux and Brian Vachowski.

Geosynthetics are synthetic materials used with soil or rock in many types of construction. They perform three major

functions: separation, reinforcement, and drainage. This report describes several types of geosynthetics; explains basic

geosynthetic design concepts for trail construction in wet areas; and provides information about geosynthetic products.

Detailed product specifications and procurement sources are listed.

Keywords: Erosion control, FHWA, geocells, geocomposites, geogrids, geonets, geo-others, geosynthetics, geotextiles,

sheet drains, trail construction, trail turnpikes

Produced by:

USDA Forest Service

Missoula Technology and Development Center

5785 Hwy. 10 West

Missoula, MT 598089361

Phone: 4063293978

Fax: 4063293719


For additional information about geosynthetics,

contact James Scott Groenier at MTDC:

Phone: 4063294719

Fax: 4063293719


Electronic copies of MTDCs documents are available

on the Internet at:

Forest Service and Bureau of Land Management

employees can search a more complete collection of

MTDCs documents, CDs, DVDs, and videos on their

internal computer networks at:

http://fsweb.mtdc.wo.fs.fed.us/search/

You can order a copy of this document using the

order form on the FHWAs Recreational Trails Program

Web site at:

http://www.fhwa.dot.gov/environment/rectrails/

trailpub.htm

Fill out the order form and either submit it electronically,

fax it to 3015771421, or mail it to:

FHWA R&T Report Center

9701 Philadelphia, Ct, Unit Q

Lanham, MD 20706

usda forest service_geosynthetics for trails in wet areas

Documents