geosynthetics

| February March 2007 | Volume 25 Number 1

Subscribe at www.geosyntheticsmagazine.info

CalTrans tackles The Merge Geogrid reinforcement is key for huge Interstate widening project

Tour the world's largest PVC membrane installation

Designer's Forum:Examining the case for the embossed

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Final Inspection:Geosynthetics, the Army Corps,

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6 | Professor Gene Wood of Clemson University checked out a trail in the Clemson Experimental Forest.

| In Situ |

| On Site |

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Geosynthetics, the Army Corps, and KatrinaBy Andrew M. AhoGMA members see and hear about progress in New Orleans

| Final Inspection |

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26 | Leak-detection testing is completed for this geomembrane installation.

40 | An examination of junctionstrength requirements.

| February March 2007 |Volume 25 | Number 1

20 | On the coverConstruction of the retain-ing walls and traffic lanes at the Interstate 5/805 “Merge” in San Diego. See page 20. Cover design by Kari Pederson.

Coming Next Issue | Retaining walls | Pavement separation | Mining | Landfill update |

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Project ShowcaseInternational Achievement Award winner:CalTrans tackles The MergeGeogrids are crucial in this five-year freeway project nearing completion in San Diego

Tour the largest PVC membrane installationBy Dominic Berube, Patrick Diebel, Andre Rollin, and Timothy D. StarkAt the desolate Salar de Atacama in Chile, massive evaporation ponds are used in mining operations

Liner integrity/leak-location survey:The significance of boundary conditionsBy Ian D. PeggsCase history examines survey of new landfill

Junction-strength requirementsfor roadway design and constructionBy Barry R. ChristopherConfused about requirements for geogrids? Read on.

EditorialYou are the best

Letters/UpdatesThank you and thanks againGeosynthetics wins gold awardUpdate: Geocells and horse trails

Designer’s ForumUsing structured geomembranes in landfill closure designsBy Ronald K. Frobel

Geosynthetic InstituteA survey of GSI surveys

PanoramaGMA-Mexico offers coursesNew ASCE officersPBS debuts ‘Design Squad’

Calendar

Advertiser Index

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| Editorial |

| Geosynthetics encourages your contributions of case histories, photos, and field tips. For submittal guidelines, contact

Ron Bygness at 800 225 4324 or +1 651 225 6988; e-mail: [email protected].

Geosynthetics (formerly GFR) is an international, bi-monthly publica-tion for civil engineers, contractors and government agencies in need ofexpert information on geosynthetic engineering solutions. Geosyntheticspresents articles from field professionals for innovative, exemplary practice.

EDITORIAL ADVISORY COMMITTEE*

Melody A. AdamsShaw Environmental Inc., USA

Andrew AhoGMA, USA

Sam R. AllenTRI/Environmental, USA

Richard J. BathurstRoyal Military College, Canada

Witty BindraPermathene Pty. Ltd., Australia

David A. CarsonU.S. EPA, USA

Daniele A. CazzuffiCESI S.p.A.

Oscar R. CouttelancGMA, Mexico

Ronald K. FrobelR.K. Frobel & Associates, USA

Stephan M. GaleGale-Tec Engineering Inc., USA

Han-Yong JeonINHA University, Korea

Robert M. KoernerThe Geosynthetic Institute, USA

Robert E. MackeyS2L Inc., USA

Kent von MaubeugeNaue GmbH, Germany

Jacek MlynarekSAGEOS, Canada

Dhani NarejoGSE Lining Technology Inc., USA

Roy J. NelsenErosionControlBlanket.com Inc., USA

Jim OlstaCETCO, USA

Ian D. PeggsI-Corp International, USA

Greg N. RichardsonG.N. Richardson & Associates Inc., USA

Marco A. SánchezML Ingeniería, Mexico

Mark E. SmithVector Engineering, Peru

L. David SuitsNAGS, USA

Gary L. WillibeyAdvanced Drainage Systems, USA

Aigen ZhaoTenax Corp., USA

*The Editorial Advisory Committee reviews selected papers, case histories, and technical editorial copy in its areas of expertise. Individual advisors do not review every submission. Statements of fact and opinion are the author’s responsibility alone, and do not imply the viewpoints of Geosynthetics, its Editorial Advisory Committee, editors, or the association.

You are the bestThis is the time of year when media outlets are

wont to deliver a series of “best of’s” from the year just passed—the best of this, the best of that. Please allow us to join in.

How about the best project using geosynthetic materials? Check out the massive, five-year-long, highway-rebuilding project in Southern California on page 20. This report describes the top prizewinner from the annual International Achievement Awards for 2006—an expansion of the Interstate 5/805 weave in northern San Diego. See how geosyn-thetically reinforced retaining walls allowed construction of additional traffic lanes, plus truck-specific bypasses, totalling up to 23 lanes wide at some points near the infamous junction that locals call simply “The Merge.”

Another “best of” for this current year: The Geosynthetics-2007 Conference and Trade Show in Washington, D.C. The Jan. 16-19 event promoted geosynthetic solu-tions for the environment, transportation, and homeland security—a “3-in-1 show” that highlighted many of the best products, best applications, and best services from the geosynthetics world.

And our magazine—known just over a year ago as “GFR,” now Geosynthet-ics—received a “best of” in 2006: Best Technical Article. With the help of a gifted engineer and writer (Enrique Álvarez) and a talented graphic designer (Heidi Han-son), Geosynthetics won a gold award for its June/July 2006 package titled “Back to the beach in Mexico: Shoreline restored with geotextile tubes as submerged breakwaters.” See page 6.

Finally, our best to all of you this new year! And when you have a “best of” your-self, please let us know. Featuring your technical expertise, geosynthetics projects, and case histories helps to keep us your best source for geosynthetics news.

| Ron Bygness, Editor+1 651 225 [email protected]


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Geosynthetics February M

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GeosyntheticMaterials Association

PUBLISHERMary Hennessy

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EDITORIAL DIRECTORSusan R. Niemi

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EDITORRon Bygness

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PRODUCTION MANAGERRussell Grimes

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GRAPHIC DESIGNERKari Pederson

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Kristen Evanson

ADVERTISING DIRECTORSarah Hyland

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ADVERTISING SALESJane Anthone, Terry Brodsky,

Suzanne L’Herault, Karen Lien, Mary Mullowney, Susan Parnell,

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© 2007 Industrial Fabrics Association International all rights reserved

The official publication of the Geosynthetic Materials Association

The official publicationof the North AmericanGeosynthetics Society

Geosynthetics (ISSN 0882 4983), is published bimonthly by Industrial Fabrics Association International, 1801 County Road B W, Roseville, MN 55113-4061. Periodicals Postage Paid at Minneapolis, MN and at additional mailing offices. Post master send address changes to IFAI, County Road B W, Roseville, MN 55113-406. Return Undeliverable Cana-dian Addresses to Station A, PO Box 54, Windsor, ON N9A 6J5. Orders and changes contact: Sue Smeed, Assistant Circulation Manager, Geosynthetics, 1801 County Road B W, Roseville, MN 55113-4061 Phone 800 225 4324 or +1 651-222 2508, fax +1 651 631 9334 e-mail: [email protected]. 1-year USA $61, Canada and Mexico $74,all other countries $102, payable in U.S. funds (includes air mail postage). Reprints: call 800 385 9402, [email protected]. Back Issues: call 800 207 0729, [email protected], www.bookstore.ifai.com.

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| Letters/Update |

| Original article written by Tom Lollis of the Clemson University Extension Service; edited for Geosynthetics

magazine by Ron Bygness.

Geosynthetics wins gold awardGeosynthetics magazine was recently cited with a Gold

Award/Best Technical Article for the story and graphics in the June/July 2006 issue titled “Back to the beach in Mexico.”

“Back to the beach in Mexico: Shoreline restored with geo-textile tubes as submerged breakwaters” was originally written by Enrique Álvarez, Ramiro Rubio, and Herbert Ricalde. The article was organized and edited by Geosynthetics editor Ron Bygness. Heidi Hanson was the graphic designer for the pack-age, which included 14 photos and 3 schematic diagrams.

Referring to the 1st-place article and graphics in Geosyn-thetics, the judges said: “Article contains many facts, formu-las, diagrams, pictures, references, etc., that are relevant to its audience. The article’s intent was to explain how a new method of beach restoration works. It used clear language, pictures, and schematics to explain the process. Though the article is written for engineers and other industry professionals, aside from the formulas, it was relatively easy to understand …“Well done. The article makes a strong case for the use of colorful tables, providing visual proof and scientific data that supports effectiveness.”

Magazines produced by the Industrial Fabrics Association International(IFAI), which includes Geosynthetics, were hon-ored Nov. 2, 2006, at the 10th annual Minnesota Magazine & Publications Association (MMPA) Excellence Awards. IFAI’s magazines were entered in the “Trade Associations–under-30,000 circulation” category and won a total of two gold, two silver, and two bronze awards.

Horses and the land: Geosynthetics help to improve riding trailsProfessor worries animal that helped tame America labelled as enviro outcast

By Tom Lollis

Clemson University profes-sor Gene Wood has two great passions—horses and the land. He hopes the two are never separated because of a dispute over natural resources.

“The horse is burned into the American psyche,” said Wood, a forest wildlife ecolo-gist. The horse carried the pio-neer westward and provided, along with the mule, “horse-power” on the farm.

No longer the beast of burden it once was, the horse

today is used for recreation. About 45% of the nation’s 9.2 million horses are used for that purpose.

“Probably a higher percentage of the 93,000 horses in South Carolina are for pleasure, primarily for trail riding,” he said.

That’s where trouble begins.“We take these 1,000-pound animals that are bred, raised,

and cared for as livestock, but thought of as pets, and use them on portions of the landscape that we have reserved for natural resource conservation purposes—in places like national and state forests,” Wood said.

In his opinion too many riders don’t know what a horse can do to the land.

“Of all the non-motorized trail users—hikers, mountain bicy-clists, and horses—the horse is the hardest on the trail,” he said.

Thanks and thanks again!

To the editor:

I just read the October/November 2006 edition of Geosyn-thetics. Thanks for your coverage of the recent U.S. Army Corps of Engineers/Steve Stockton presentation to your Geo-synthetic Materials Association Executive Council.

Also, thanks for GMA’s support of the Water Resources Development Act of 2006. It is good to know that organizations like yours are supporting this important Act.

Thanks again for a great magazine!

Scott StoddardIntermountain Rep/Civil EngineerCorps of EngineersBountiful, Utah

| Erosion-control trail building was featured in the February/March 2006 issue of Geosynthetics.


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| Update |Photos 1 and 2 by Diane Palmer/Clemson PSA Media Relations

Photos 1 and 2 | Professor Gene Wood of Clemson University checked out a trail in the Clemson Experimental Forest.

Over time trail riders often leave be-hind gullies, eroded stream banks, silted streams, angry land managers, and envi-ronmentalists calling for a ban on horses on wildlands.

It doesn’t have to be that way, accord-ing to Wood, who owns five horses and enjoys a good trail ride himself.

“We can preserve the ecological in-tegrity of the forest and use our horses out there for recreation at the same time,” he said.

The keys are well-designed, well-constructed, and well-maintained trails along with appropriate behavior by horse riders.

“Farmers learned to plow on the con-tour to reduce erosion. Trails should fit the contour of the land as well,” he said.

One technique tested on the Clemson trail system—and elsewhere around the country—is the use of geosynthetic ma-terials such as geotextiles and geocells

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| Update |

filled with gravel. These materials help hold the aggregate in place so it won’t be displaced by horse hooves.

(For example, photos 3 and 4 show trail construction in the Geauga Park District in Ohio, as described in the Feb./Mar. 2006 issue of Geosynthetics magazine. Photo 3:Installation of 6-in. geocells directly on the trail to promote reinforcement and proper

drainage. Photo 4: And then trail comple-tion with cover aggregate and horizontally installed water-bar timbers.)

Wood has been figuring out the de-tails since the early 1990s by working with the 100 miles of shared-use trails in the Clemson Experimental Forest and organizing national and regional trail conferences.

Finally he has put what he has learned into a book—Recreational Horse Trails in Rural and Wildland Areas.

Funded by the Federal Highway Ad-ministration’s Recreational Trails Pro-gram with funds channeled through the American Horse Council to Clemson University, the book will be published by the USDA-Forest Service Missoula Technology and Development Center (MTDC) as a public property.

The book is expected to be available free on the MTDC Web site this year. Hard copies will also be made available for free by the USDA-Forest Service.

Wood teaches the basics of ecology in the first chapter, showing horse owners that soil is not just dirt.

Soils vary in sensitivity.“In some situations you can use the

horse a lot without damaging anything,” he said. “If a trail has little or no stone

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in it, and it’s muddy, riding a horse at a fast pace will destroy that trail.”

Wood’s book contains advice on proper trail construction. The worst trail is one that goes straight up a down a slope, a fall-line trail. It will always turn into a gully. he said.

Wood also said that to protect the nat-ural resources riders should not ride up and down streambeds. They should stay off stream banks as much as possible.

He encourages land managers to learn how to construct appropriate stream crossings for horses for hydration.

Wood believes that the key to pre-serving the privilege of riding on pub-lic lands is for horse users to become as sophisticated about natural resources as organizations such as Ducks Unlimited and the National Wild Turkey Federation.

Wood has been spreading his message nationwide since 1998 when Clemson

University hosted the National Confer-ence on Horse Trails in Forest Ecosys-tems. From that event, Wood developed a plan for an annual Southeastern Eques-trian Trails Conference.

It was hosted by Clemson from 2000 to 2002, then rotated among other Southern states. It will return to South Carolina in 2008.

Reference

Shepard, Kathy, “Happy Trails: Erosion control and effective drainage,” Geo-synthetics, February/March 2006 (Vol. 24, No. 1), pp. 26-29.

Photo 4



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| Designer’s Forum |

Using structured geomembranes in finalsolid-waste landfill closure designsBy Ronald K. Frobel, MSCE, P.E.

IntroductionSlope failures on final cover systems for solid-waste land-

fills have been well-documented during the past 20 years with many failures of note within the past three years. Sliding failures have occurred despite known geotechnical reasons for failures and known design methods to avoid slope failures. Many of these failures occur at interfaces with the geosynthet-ics—most notably at the geomembrane/geotextile interface or geomembrane/soil interface.

Early failures in the 1980s prompted manufacturers to develop and provide an alternative geomembrane with a “textured” surface that increases frictional characteristics and thus increases the fac-tor of safety against sliding failures. However, the most common type of “texturing” manufactured by the blown-film coextrusion process (HDPE and LLDPE) has proven less than acceptable in both surface frictional values and quality of sheet (inconsistency in asperity height, textured surface, and cross-roll friction values). Deficiencies in quality and lower-than-expected asperity height have led to recent slope failures (Sieracke, 2005).

Structured or embossed HDPE and LLDPE geomembranes have been available to the civil engineering community and landfill owners and designers for more than 10 years. Their use in final closure designs has been steadily increasing, especially during the past five years, as owners and designers discover and demand the consistently high quality textured and/or structured characteristics of this type of geomembrane due to the unique manufacturing process that incorporates flat-die extrusion and embossed calendars.

This paper will focus on the structured or embossed geo-membrane concept and manufacturing process, as well as pre-senting comparative properties for consideration in design.

Surface texturing methods forHDPE and LLDPE

The following paragraphs will briefly describe and discuss the two primary surface texture methods in use currently in North America. Other methods such as surface impingement are available mostly outside of North America and will not be discussed in this paper.

Structured (embossed) geomembrane texture

During the flat-die manufacturing process for geomem-branes, a hot extruded polymer sheet is run between two coun-ter-rotating hot embossing rollers that contain uniform struc-

tural die shapes to form a molded or “embossed” structured or textured surface that is an integral part of the sheet without affecting the core thickness. This method has been in use for more than 20 years and was designed to overcome problems of non-uniformity, variable area coverage, variable peaks and val-leys, variable thickness, and reduction in mechanical properties that are commonly found with the coextrusion process.

| Ron Frobel is the owner/principal, R.K. Frobel & Associates Consulting Engineers, Evergreen, Colo. He is a member of

Geosynthetics magazine’s Editorial Advisory Committee.

The Designer’s Forum column is refereed by Greg Richardson, Ph.D., P.E., of G.N. Richardson & Associates, www.gnra.com.


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Figure 1 | Flat-die calendaring manufacture (smooth-sheet production)

Figure 2 | Flat-die molded textured surface (surface-friction profile)

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arch 2007

by the shearing action of the extruder breaking bubbles formed by the cooling of the blowing agent (nitrogen gas) as it expands. This process is known to be highly variable from manufacturer to manufacturer and even within a single roll or across a roll width.

Although the texture cannot be separated or peeled off, the critical mechanical characteristics of the sheet (i.e., tensile stress, strain, tear, and multiaxial response) are substantially reduced due to the introduction of peaks and valleys or surface imperfections that are not found on a smooth sheet. Addition-ally, non-uniformity of core thickness and even the method used to determine thickness has been questionable and is often a debate in CQA acceptance testing.

Figures 4 (above) and 5 (p. 14) provide examples of the sur-face texture generated by the process.

Figure 4 | Coextruded surface texture (blown-film process)

Figure 1 is a photo illustrating the production method, and Figures 2 and 3 provide examples of the surface texture gener-ated by the flat-die molded surface manufacturing process. A major advantage of structuring is the ability to create very differ-ent surface textures on the upper and lower geomembrane sheet surfaces, thus customizing the specific application (i.e., drainage on top and aggressive friction surface on the bottom).

Coextrusion geomembrane texture

During the blown-film coextrusion process, molten polymer is extruded in two or three layers through concentric ring dies that are up to 10m (32.8 ft.) in circumference. The outer and inner dies are used to produce layers that can be “textured” or roughened by intro-ducing and allowing nitrogen gas to escape. The texture is formed

Figure 3 | Flat-die molded structured surface (drain-surface profile)

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Comparative properties for design considerations

In addition to the noted differences in surface texturing methods and noted in-consistencies from roll to roll or within rolls on coextruded textured geomem-branes as discussed above, the follow-ing considerations should be examined during design and ultimate selection of a textured geomembrane.

Potential for mechanical

properties reduction

Reduced mechanical properties of a required sheet thickness due to a texturing process such as coextrusion must be con-sidered, especially for the long term where increasing stresses due to subsidence or localized settlements will occur and affect the out-of-plane (multiaxial) response as well as seam strengths under stress.

Reduced tensile strength and strain to rupture under load will also occur due to increased susceptibility to environmental stress cracking again due to the introduc-tion of notches or imperfections caused by the coextrusion process. Using the flat-die extrusion process, the geomembrane me-chanical tensile, elongation and other prop-erties are closer to the values of smooth sheet and do not change from roll to roll as imperfections or thickness variations are not introduced during manufacture.

Interaction at the shear surface

Depending on the project design re-quirements (i.e., steep slopes, seismic

response, construction, and service load-ing) the peak and large displacement (post-peak) interface strengths must be taken into consideration. For example, according to Stark and Richardson (2000) and Richardson and Theil (2001),

coextruded textured geomembranes ex-hibit large post-peak strength loss against geotextiles due to geotextile fiber tear-ing, pullout, and shear orientation.

In addition to geotextile fiber/texture interaction, the texture itself may comb (lay over) causing greatly reduced post peak shear strength (Stark and Rich-ardson, 2000). But embossed surface textures exhibit higher interface shear strength and lower post-peak strength loss at lower normal stresses commonly found in landfill closure designs.

Constructability with geotextile surfaces

Some designs require the field place-ment of a textured geomembrane directly on a geosynthetic clay liner (GCL) or placement of a geonet composite or geo-textile directly over the textured geomem-brane surface. This requires interfacing a nonwoven geotextile with the textured surface. The “Velcro® effect” or “hook-and-loop” adhesion to a coextruded tex-

Figure 5 | Coextruded surface texture (blown-film process)

Design Consideration Coextruded Embossed

Consistent Thickness (cross roll) No Yes

Consistent Texture (cross roll) No Yes

Consistent Asperity Heights No Yes

Asperity Heights >15 mil No Yes

Consistent Shear Testing (cross roll) No Yes

Effect on Multiaxial Stress-Strain

(Settlement/Subsistence)Yes No

Texture Combing during Shear Yes No

Post Peak Reduction in Shear Strength Yes Yes

Easily Placed with Geotextile Surfaces No Yes

Increased QC and CQA Costs Yes No

Table 1 | Summary of Comparative Properties for Design Considerations

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tured surface is often problematic during field placement and requires very careful positioning or the use of a slip sheet.

Embossed geomembrane surfaces, on the other hand, allow positioning of geo-textiles and geocomposites without major difficulty. Quantifying of the “hook-and-loop” phenomenon has been the subject of extensive testing and, in particular, testing the effects on interface shear and the textured surface during shear (He-beler, G. L., et.al., 2005; Giroud, J. P., 2004; Frost, J. D., et.al., 2002).

Geomembranes manufactured with textured surfaces by embossing provide consistent uniform quality texture that will supply the requisite interface shear strength without the detrimental effects of the coextrusion-blown film manufacturing process. Additionally, as regards CQA field testing and laboratory conformance testing, structured or embossed textured geomem-branes will provide a consistent value from roll to roll and across the roll width, thus providing requisite design reliability.

This is not the case for coextruded, blown-film, textured geomembranes where “the consistency of the textur-ing both across the roll and roll to roll should be a concern to the engineering community … What good is direct shear testing if the material provided is not consistent with respect to texturing?” (Sieracke, 2005).

Table 1 is a summary of several de-sign considerations that should be ad-dressed when selecting a textured geo-membrane to enhance slope stability factors of safety.

Quality measurementsTo properly determine the quality and

specification conformance of a blown film coextruded texture, multiple loca-tions of discrete measurements must be made using two mechanical test methods, namely ASTM D 5994 “Test Method for Measuring the Core Thickness of a Textured Geomembrane” and GRI Test Method GM 12 “Asperity Measurement

of Textured Geomembranes Using a Depth Gage.”

Due to the non-uniform surface, many discrete locations across a full roll width must be tested and averaged with maxi-mum and minimum values. The testing technician tries to obtain the lowest core thickness and the highest asperity height by adjusting measurement locations primarily based on observation. “Both methods have proven to be problematic and have led to numerous conflicts be-tween manufacturer and specifier” (G.R. Koerner and R.M. Koerner, 2005).

Alternative methods to determine these elusive properties have been the subject of several studies and papers (G.R. Koerner and R.M. Koerner, 2005; Yesiller, N.,2005). Structured or em-bossed geomembrane surfaces (tex-tures), on the other hand, are consis-tent in both core thickness and asperity height due to the manufacturing pro-cess. Thus, multiple measurements to determine average or minimum values

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are not necessary in QC and CQA test-ing for structured geomembranes.

Large-scale, direct-shear

performance testing

The interface strength of contact sur-faces and in particular interface frictional strength must be determined for the geo-membrane/geotextile and geomembrane/soil combinations using project specific geosynthetics, site specific soils materi-als, expected loading conditions, mois-ture/density conditions, etc. Mostly, these surface friction determinations are made by experienced personnel in an accredited geosynthetics laboratory using a large-scale, direct-shear box in general accor-dance with ASTM D 5321 “Standard Test Method for Determining the Coefficient of Soil and Geosynthetic or Geosynthetic and Geosynthetic Friction by the Direct Shear Method” (ASTM, 2006).

This testing has become an essential part of the design process as well as CQA programs that qualify materials for construction. The surface texture consistency is extremely important in this regard and must not change signifi-cantly within a roll or from roll to roll. In fact, this has been problematic for coextruded textures that may be tested only once on a sample from the manu-facturer vs. what is actually installed in the field and has led to failures due to lower than expected shear strength. If the textured surface of the material actu-ally received in the field is questionable, it is recommended that performance tests be carried out on roll goods that are received on-site to verify requisite interface shear properties.

Asperity height

Additional to the requirement for a consistent textured surface, the minimum value of asperity height must be con-sidered (assuming it can be accurately measured). Current specification require-ments call for a minimum of 10 mils and reflects GRI Standard GM 13 and 17. However, 10 mils may be considered insufficient for many applications and should be increased to a minimum of at least 15 mils to compensate for known lower values that will be encountered in the coextruded manufacturing process.

Both coextruded and structured geomem-branes can meet the 15-mil minimum.

Types of structured/embossed textures

There are generally three types of structured surfaces available to the design engineer for MSW closure applications:

• General slope applications against soils and geotextiles—25-mil asperity height

• Aggressive slope applications with integral drainage—175-mil asperity height

For general slope applications on slopes of 3H:1V or less, the embossed textured material (refer to previous in Figure 2). provides consistent interface shear values against a variety of soil types. Table 2 illustrates the interface shear values that can be expected with various soil types as well as a nonwoven geotextile. As with all slope designs,

Figure 6 | Bottom embossed structured or spike surface

Cap Loading Conditions—ASTM D 5321

Material Peak Adhesion LD Adhesion Efficiency

Coarse Sand 34º 65 psf 32º 15 psf 92%

Lean Clay 37º 110 psf 32º 30 psf 97%

Silty Sand 32º 55 psf 28º 10 psf 100%

NW GT 32º 80 psf 17º 80 psf NA

Notes: LD = Large Displacement; NW GT = Nonwoven Geotextile on Geonet Composite

Cap Loading = 250, 500, 1000 psf; Saturated Conditions

Table 2 | Representative Interface Shear Values—Embossed Texture

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large scale performance testing is en-couraged using site specific soils and moisture/loading parameters. Aggressive or steeper slope applications are pos-sible with the structured spike (bottom) surface as shown in Figure 6.

Integral top surface drainage

Structured geomembranes are also manufactured to provide an integral top

surface drainage by incorporating a 145-mil stud profile. The top surface of the stud profile is overlain with a nonwoven geotextile for retention of drainage soil placed on top of the structure. Under nor-mal load, the geotextile will intrude into the drain space as with geonet compos-ites. The transmissivity of the drain layer is similar to geonet composites under cap loading conditions without the require-

ment for a geonet composite resulting in substantial cost savings per acre.

Additionally, the potential for lower than designed interface shear values of a geonet composite against a textured surface is eliminated. The geotextile, once embedded into the stud profile, pro-vides for excellent interface shear values against overlying soil with efficiencies greater than 95%. Figure 7 shows a typi-cal structured geomembrane stud profile placed on a cap prior to geotextile and soil cover placement.

Based on project specific labora-tory conformance testing incorporating site soils, transmissivity values of the drain stud profile with a nonwoven geo-textile and soil/cap loading conditions range from 1.1E-03 to 3.6E-03m2/s at a gradient of 0.33. Table 3 illustrates transmissivity test values for a cap load-ing condition after 100 hours testing under load. The nonwoven geotextile initially intrudes into the drain structure during increasing normal load similar to geonet composites.

8 oz/sy Nonwoven Geotextile over 145-mil Drain Stud Profile

Normal Load Gradient Transmissivity Flow Rate(psf) (i) (m²/s) (gpm)

250 0.25 1.19E-03 1.44

250 0.33 1.11E-03 1.77

250 0.50 9.77E-04 2.36

Table 3 | 100 Hour Transmissivity Test Results

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SummaryStructured or embossed HDPE and

LLDPE geomembranes are not new to the geosynthetics industry and design engineers and, in fact, have been used in a variety of civil engineering appli-cations for more than 10 years. Their

use in MSW closure applications has been steadily increasing during the past 5 years. The advantages of this type of textured or structured geomembrane are many, including:

• Integral texture or structure em-bossed within the sheet

• Customized texture or structure top and/or bottom sheet surfaces

• Consistent texture, structure and core thickness from roll to roll or within a roll

• Consistent and reliable interface shear properties from roll to roll or within a roll

• Consistent mechanical and multi-axial strain properties

• Steep slope applications potential (aggressive spike profile surface)

• Integral surface drainage potential (drain stud profile surface)

• Cost-effective in QCA cost reduc-tions (both field and laboratory)

• Cost-effective alternative to geonet composite placed over a textured sheet (structured drain profile)

It must be emphasized that project specific specifications and performance testing regarding required performance characteristics for a textured geomem-brane is the design engineer’s responsi-bility. The design engineer must be aware of the differences in the available types

Figure 7 | Structured drain profile on a slope prior to geotextile/cover soils placement

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www.geosynthetictesting.com



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of textured materials and develop design specifications and CQA plans that will ultimately satisfy project requirements regardless of the material supplied.

ReferencesAmerican Society for Testing and Ma-

terials International (ASTM), 2006. ASTM D 5321 “Standard Test Meth-od for Determining the Coeffi cient of Soil and Geosynthetic or Geosyn-thetic and Geosynthetic Friction by the Direct Shear Method”, Vol 04.13, Geosynthetics, ASTM Annual Book of Standards, ASTM, West Con-shohocken, Pa.

American Society for Testing and Ma-terials International (ASTM), 2006, ASTM D 5994.

“Standard Test Method for Measuring the Core Thickness of a Textured Geo-membrane”, Vol 04.13, Geosynthetics, ASTM Annual Book of Standards, ASTM, West Conshohocken, Pa.

Geosynthetic Research Institute (GRI), 2004. GRI Test Method GM 12, “Asperity Measurement of Textu-red Geomembranes using a Depth

Gage”, GRI Test Methods and Stan-dards, Geosynthetic Institute, Phila-delphia.

Frost, J. D., Evans, T. M., Hebeler, G. M. and Giroud, J. P., 2002. “Infl u-ence of Wear Mechanisms on Geo-synthetics Interface Strengths”, Proceedings of the 7th International Conference on Geosynthetics, Nice, France, September, 2002, Vol. 4, pp. 1325-1328.

Giroud, J. P., 2004. “Quantitative Anal-ysis of the Impact of Adhesion Be-tween Geomembrane and Geotextile on the Stability of Soil-Geosynthetic Systems on Slopes”, J. P. Giroud Inc. Technical Note, 2004.

Hebeler, G. L., J. D. Frost, A. T. Myers, 2005. ”Quantifying hook and loop in-teraction in textured geomembrane-geotextile systems”, Geotextiles and Geomembranes International Jour-nal, Vol. 23, pp. 77-105.

Koerner, G. R. and R. M. Koerner, 2005. “Ultrasonic Thickness Testing of Tex-tured Geomembranes”, Proceedings Geo-Frontiers 2005, ASCE.

Richardson, G. N. and Theil, R. S., 2001. “Interface Shear Strength: Part

1—Geomembrane Considerations”, Geotechnical Fabrics Report (GFR), Vol. 19, No. 5, IFAI, Roseville, Minn., pp. 14-19.

Sieracke, M. D., 2005. “Geosynthetic Manufacturing Concerns from a Consultant’s Perspective”, Proceed-ings GRI/NAGS Conference, Las Ve-gas, December, 2005.

Stark, T. D. and Richardson, G. N., 2000. “Flexible Geomembrane In-terface Strengths,” Geotechnical Fabrics Report (GFR), Vol. 18, No. 3, IFAI, Roseville, Minn., pp. 22-26.

Richardson, G. N. and Theil, R. S., 2001. “Interface Shear Strength: Part 1—Geomembrane Considerations”, Geotechnical Fabrics Report (GFR), Vol. 19, No.5, IFAI, Roseville, Minn., pp. 14-19.

Yesiller, N., 2005. “Core Thickness and Asperity Height of Textured Geo-membranes: A Critical Review”, Geo-technical Fabrics Report (GFR), Vol. 23, No. 4, IFAI, Roseville, Minn., pp. 14-16.

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www.geosyntheticbarriers.com

| The lower one-third portion of the massive retaining wall for the Interstate 5/805 bypass lanes is seen here. The wall was built last fall.

Project Showcase

| Information provided from the IAA competition entry forms; Ron Bygness, editor of

Geosynthetics, also contributed to this article.

From the 2006 International Achievement Awards for Geosynthetic Projects

Five-year CalTrans freeway project is nearing completion in San Diego

All photos courtesy of TenCate Geosynthetics

IAA Award of Excellence

TenCate Geosynthetics

Pendergrass, Ga., USA

Geosynthetic-reinforced plantable wall system

Interstate 5/805 widening project

San Diego County, Calif.

IntroductionIn an effort to reduce traffic congestion and improve safety

conditions in northern San Diego, the California Department of Transportation (CalTrans) is adding lanes and creating a truck bypass at the Interstate 5/805 junction. A unique portion of this project is the construction of a plantable, geosynthetic-reinforced retaining wall that transforms a simple slope into a

vertical face that supports additional lanes of the reconstructed freeway.

A two-phased building system allows the attachment of a mas-sive retaining wall, with layers of engineered fill wrapped with high-strength, woven geogrid, to a concrete facing system that protects the exposed geosynthetic while a polypropylene geotex-tile holds loose plantable topsoil to facilitate vegetative growth.


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‘The Merge’There were days when traffic on the Interstate 5/805 junc-

tion in Sorrento Valley north of San Diego was backed up for literally hours. CalTrans estimated that more than 261,000 vehicles passed through this mother of all bottlenecks—known locally as “The Merge”—every weekday.

That is why a $190 million road-improvement project—the most expensive ever in San Diego County—has been in progress for five years and will be completed this year. At it widest point, the reconfigured freeway will consist of an unheard-of, football field-wide 23 lanes: seven conventional lanes and four bypass lanes in each direction, plus a northbound carpool lane.

The Merge is one of the busiest Interstate segments in the country, and it serves as the major entryway into San Diego from the northern part of the county as well as Orange County

| A quarter-mile stretch of geogrid reinforcement awaits final inspection from CalTrans officials before it is covered with compacted fill.

| Fill is placed over the geogrid reinforcement.

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Project Showcase

and Los Angeles. Reconstruction on the roadway began in 2002. By 2005, new northbound lanes opened. The new southbound lanes will open this year.

Traffic on The Merge doubled in the past 15 years. And CalTrans estimates say it will double again in about another 10 years—a total of more than half a mil-lion vehicles on average each weekday.

Building the wallTo support these new lanes of traffic,

CalTrans engineers designed a huge geo-synthetic-wrapped retaining wall with a massive concrete basket system at its face. This two-part method allows the construction of a retaining wall, with layers of engineered fill and high-strength, woven geogrid attached to a concrete facing system that protects the

geosynthetic exposed at the face and holds loose plantable topsoil to facilitate vegetative growth.

The concrete facing portion of the wall has tiers of headers that extend into the geosynthetically reinforced backfill and stretchers that extend between head-ers to form the front face of the wall. These stretchers, with the help of non-woven geotextile-bridged gaps between the stretchers, hold in loose topsoil so that vegetation will grow easily at the face of the wall.

The tremendous soil forces generated behind the concrete tiers are sustained by layers of geogrids that extend up behind the stretchers and then back into the back-fill. The end result is a massive, near-ver-tical retaining wall more than 65 ft. high that will be completely vegetated.

GeosyntheticsCalTrans required extensive labora-

tory testing of the geosynthetic materials before they could be approved for use in this project. Aggressive installation dam-age testing was performed to demonstrate their resistance to damage when exposed to sharp angular rock under heavy loads.

Creep testing (how much a geosyn-thetic will stretch under a century of sus-tained loading) was also performed on all the geosynthetic materials required to hold soil loads in the foundation and the retaining wall. The geosynthetics chosen for use on this project were manufac-tured out of high-tenacity polyester that demonstrated high creep resistance and long-term durability.

The construction of this 65-ft.-high structure proved problematic from sev-

| Concrete stretchers, lined with filter geofabric, contain loose topsoil for growth of vegetation at the face of the retaining wall.

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Project Showcase

eral sources. CalTrans set stringent re-quirements for the geosynthetic-wrapped facing of the wall. It also required high compaction of the fill, even adjacent to the geosynthetic-wrapped face, to limit any differential settlement that may point load sections of the concrete stretchers.

Further, the geogrid was cut to fit around each concrete header. The con-tractor had to develop a system to keep the geosynthetic-wrapped face square, achieve proper compaction adjacent to the geosynthetic face, and keep the geo-synthetic extremely tight and in place during the entire process.

Maintaining high soil compaction within the geosynthetic-wrapped sections proved particularly challenging on this project. The contractor developed a set of wood forms that held the geosynthetic square and in place while compacting the fill adjacent to the geosynthetic face. Only hand-held compaction equipment would fit between the headers, which slowed production significantly and made achiev-ing compaction even more difficult.

Once the compaction was completed, the wood forms were removed to reveal a densely compacted geosynthetic-lined face that was completely square and al-most hard as stone that was then subject to approval by on-site CalTrans person-nel. This tedious process of wrapping fabric between the headers was repeated in 5-in.(0.13m) vertical increments in the lower section of the wall and increased to as much as 19-in.(0.5m) vertical incre-ments at the top of the wall.

CalTrans officials approved each com-pacted, geogrid-wrapped section.

CompletionThe foundation of the plantable geosyn-

thetics-reinforced retaining wall also used geosynthetic reinforcement. Two layers of geogrid were placed within a gravel blan-ket to form a reinforced foundation mat-tress (geosynthetics helped keep the gravel from spreading laterally while under load) to support the retaining wall structure with minimal differential settlement. The entire blanket was wrapped in geotextile.

When all the dust settled, approxi-mately 1 million yds.2 of geosynthetics were used to construct this project. The total wall face is more than 200,000 ft.2

(18,581m2) with heights of up to more than 65 ft. (21m) and a length of more than 3,000 ft. (938m). The project con-sumed a total of more than 815,000 yds.2

(681,422m2) of geogrid products.

Editor’s Note:

The Industrial Fabrics Association Inter-national (IFAI) invites entries for its 2007 International Achievement Awards com-petition. For more information about the IAAs, contact Christine Malmgren, +1 651 225 6926, [email protected].

Project HighlightsOwner: California Department of

TransportationLocation: Interstates 5/805 junction, San Diego County, Calif.Project duration: 2002–2007Manufacturing: TenCate GeosyntheticsGeogrid: Mirafi Miragrid 10XT, 7XT,

5XT, 3XTNonwoven geotextile: Mirafi 140NC


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LockLoad_0207GS-FP.indd 1 12/12/06 11:00:27 AM0207GS_Cv2_25.indd 25 1/8/07 1:16:42 PM

www.lock-load.com

| 1International Sales Manager, Solmax International, 2801, Boulevard Marie-Victorin, Varennes, Quebec Canada J3X 1P7, (800)

571-3904 ext. 206, e-mail: [email protected] 2Technical Director, Canadian General Tower, 52 Middleton, P.O. Box 160, Cambridge, Ontario N1R 5T6, Canada, 519-623-1630,

e-mail: [email protected] 3Director, Solmers International, 1471, boul, Lionel-Boulet, Bureau 22, Varennes, Quebec Canada J3X 1P7, 514453-6998,

e-mail: [email protected] 4Professor of Civil and Environmental Engineering, University of Illinois, 205 N. Mathews Ave., Urbana, IL 61801, 217-333-7394,

e-mail: [email protected]

Massive mining evaporation ponds constructed in Chilean desert| The Salar de Atacama in Chile is the site of the largest PVC geomembrane installation in the world—more than 16 million m2 utilized in mining operations since 1996.

By Dominic Berube,1 Patrick Diebel,2 Andre Rollin,3 and Timothy D. Stark4


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7 Photo 1 | In constructing the evaporation ponds, after the PVC liner is deployed, electrical leak-detection tests are done (see page 32).

Photos courtesy of Solmax International unless cited

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Photos 2a and 2b | Air-channel testing of the field seaming (see page 31).



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The largest PVC geomembrane installation in the world is so immense that it can be seen from an orbiting space shuttle.

The site is in the arid and isolated Atacama Desert region in northern Chile where these membrane applications helped create huge salar (“salt”) evaporation ponds. This is a project that extracts natural resources through evaporation and crys-tallization of naturally occurring brine solutions and develops them into products such as sodium nitrate, potassium nitrate, potassium sulfate, and other specialty blends.

Where in the world?The Salar de Atacama is located at the foot of the Andes

Mountains (68° 24’ South, 23° 30’ East) at an elevation of 7,000 ft. (2,130m) in northern Chile, covering an area of approximately 1,800 mi.2 (3,000km2). This area is near the Atacama Desert, one of the driest regions in the world. The site is situated near Chile’s borders with Bolivia and Argentina. One of the most mineral-rich stretches of the Atacama region is known as the Salar de Atacama.

The Atacama Desert is a sun-drenched, virtually rainless plateau at the foot the Chilean Andes. The Salar de Atacama is an ancient seabed underlain by large reservoirs of liquid brine that is home to the world’s third-largest expanse of salt flats.

Sociedad Quimica y Minera de Chile S.A. (SQM), with headquarters in Santiago, Chile, is one of the world’s largest producers of specialty fertilizers, iodine, lithium, and other industrial chemicals. Many of the components of those prod-ucts are extracted from the geomembrane-lined salar ponds operated by SQM.

In 2004, SQM began increasing its production of potassium chloride with the addition of two 300,000m2 evaporation ponds in the salar region, where operational and environmental con-cerns dictated the use of an impervious geomembrane system.

The processSQM has two production facilities at the salar. To mine the

potassium and lithium salts, large amounts of brine are pumped to the surface by wells. The pumped brine is conveyed via canals and directed into the large, lined evaporation ponds. Clouds rarely form or persist over this region, and the area is extremely windy, providing an ideal environment to evaporate the large amounts of water required to deliver the brine into the ponds.

As a first step in the extraction process, a number of large pre-concentration ponds are constructed where, by taking advantage of the evaporation process, a portion of the sodium chloride in the brine is allowed to precipitate as an “undesir-able by-product.”

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After a residence time, the now-con-centrated brine is pumped into produc-tion ponds where the dry salt-mineral produced is mechanically removed and stockpiled.

Some of the important salts precipitat-ing from the brine are: sodium chloride, potassium (often used for fertilizer), lith-ium, and boric acid as a by-product. SQM is a leader in production of salts used in fertilizers and provides 35% of the world’s lithium, a component for batteries, phar-maceuticals, and sapphire glasses used in jewelry and aeronautics applications.

Potassium and lithium are produced in different ponds via a three-stage process. The product is mechanically routed to an on-site, chemical-processing facility where the desired minerals are extracted. Then the extremely concentrated brine

is pumped to a fourth-stage pond for recovery of boric acid.

The underground brine is recharged, albeit at a reduced rate, by the melting snowcaps in the surrounding mountains. As the recharge water flows through the underground bedrock it dissolves the minerals in the sediment of the ancient seabed forming the concentrated brine. The concentrated brine is then pumped to the ground surface and contained in the ponds lined with PVC geomembranes.

Photo 3 shows one of the ponds filled with brine and undergoing evaporation.

After the water evaporates, the ponds are carefully mucked out, with the salts acting as a protection layer so the liner system is not damaged. For example, the bottom salt layer protecting the liner is sodium chloride in the ponds where

sodium chloride is precipitating, potas-sium in ponds where potassium is form-ing, and lithium in the lithium production ponds. After the salts have been partially removed, the pond can be refilled and used repeatedly.

Holes in the geomembrane are ex-tremely detrimental because the brine can flow out and return to the subsurface reservoirs. Not having holes in the geo-membrane is important because it takes approximately one year to yield about 1m of salt, i.e., one year to evaporate a typical pond. Thus, losing brine and hav-ing to restart the process after patching a liner hole is time-consuming, costly, and reduces the annual production quantity.

In addition, holes in the geomembrane are difficult to detect because of the pres-ence of muck, so it is imperative that the

Photo 3 | A brine-filled evaporation pond at the Salar de Atacama in northern Chile. This photo shows one of the ponds filled with brine and undergoing evaporation. A pumping station in the brine-filled pond is shown in foreground. In the background are piles of extracted sodium chloride salt, with the Andes Mountains in the far background of this shot.

Photo courtesy of Patrick Diebel

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includes Keystone Retaining Wall Systems®, Bin-Wall, Vista DSM™, Metric Sheeting, Tensar® Geogrids, LANDLOK™ Turf

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Chile Ponds

geomembrane have excellent chemical resistance and resistance to pinholes in manufacturing, fabrication, deployment, and use. The properties that PVC has—high elongation and the tendency to drape around any protrusions on the compacted layer underneath the liner—helps mini-mize the occurrence of small holes and brine loss.

Photos 4a-c show the evolution of an evaporation pond, with the final liner in-stallation completed (a), the preparation for the brine to fill (b), and the gradual filling of the pond with brine (c).

These geomembranes are a likely choice for this application even though it is a harsh environment. The mem-branes are durable and offer excellent chemical resistance to the salts, which is important because of the long-term exposure of the geomembranes to the brine. PVC geomembranes also exhibit smaller wrinkles than some other geo-membranes when installed because of a lower expansion coefficient, higher sub-grade/geomembrane interface strength, flexibility (Photos 4 and 5).

This is especially significant in this particular application because the smaller wrinkles result in substantial intimate contact between the geomembrane and subgrade and the protective salt layer. The benefit of intimate contact is a re-duction in the lateral flow from a hole or leak in the geomembrane.

Liner system design and installation

The evaporation ponds have average dimensions of 10 ft.(3m) deep, 1,000 ft.(300m) wide, and 3,000 ft.(1,000m) long. The liner system of the first ponds consists of compacted soil PVC geomem-brane. The current liner system utilizes nonwoven geotextile over a compacted natural salt layer PVC geomembrane.

To reduce field seaming in this harsh environment, the PVC geomembrane was fabricated into panels at the factory, a controlled environment that is more suitable for high-quality seaming than on-site at the salar. The panels are typi-cally about 50 ft.(15m) wide and 1,000 ft.(300m) long when shipped to the site. Thus, the only field seaming required is the seaming of the panels. The panel

Photos 4a, 4b, 4c | A new evaporation pond, with the final liner installation completed (a), the pond in preparation for the brine (b), and brine filling the pond (c).

a

b

c

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Chile Ponds

size is usually limited by an allowable field handling weight, so a typical panel weighs about 6,600 lbs.(3,000kg).

The PVC geomembrane is field-seamed using a solvent or thermal fu-sion. With the thermal fusion method, a hot-wedge or hot-air welder is used. Thermal fusion is now the recommended technique because the produced seam can be air-channel tested if a dual-track weld is performed.

Testing of field seams and completed liner

A dual-track field seam was speci-fied by SQM as the primary seaming method for the pond linings that were installed in 2004. Given the high cost of pumping and storing the brine, a seaming process that allowed the testing of the en-tire length of the field seams, instead of isolated areas with destructive samples, was sought. This resulted in the use of dual-track welds and air-channel testing of the field seam (Photos 2a, 2b).

The air-channel testing of PVC field seams has gained popularity and provides a number of advantages over destructive testing of seams. One advantage is that the air-channel pressure can be used to verify the seam peel strength specified by the PVC Geomembrane Institute (PGI 2004) of 2.6 N/mm (15 lbs./in.), using the sheet temperature and a relationship presented by Stark et al. (2004) and shown in Figure

1 (page 32). This relationship is incorpo-rated into the new ASTM Standard Test Method D7177 (ASTM 2005) for air-chan-nel testing of PVC field seams. Thus, if the air-channel holds the required pressure, the frequency of destructive sampling and testing is less.

The harsh desert environment pro-duced sheet temperatures in excess of 158°F (70°C), making air-channel testing a challenge. Sheet temperatures greater than 158°F (70°C) are particularly challenging because the relationship between the air-channel pressure and the geomembrane sheet temperature for the PGI-specified seam peel strength of

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0207GS_26_45.indd 31 1/8/07 1:42:08 PM


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2.6 N/mm (15 lbs./in.) in ASTM D7177 extends to a sheet temperature of 120°F (48°C), as seen in Figure 1.

Testing is currently being conducted to overcome this limitation. In the interim, the relationship shown in Figure 1 (i.e., the relationship between air-channel pres-sure and geomembrane sheet temperature included in ASTM D7177) is extended to cover the range of sheet temperatures encountered on this project. Thus, the air-channel pressure required for the PGI-specified seam peel strength of 2.6 N/mm (15 lbs./in.) is about 60 kPa (9 psi) for a sheet temperature of 158°F (70°C).

Another advantage of air-channel test-ing of field PVC geomembrane seams is the flexible nature of these geomembranes that allows the inflated air-channel to expand like an inflated bicycle tube. This allows a visual examination of the entire inflated seam and identification of any seam defects even though the seam may pass the required air-channel pressure. These defects are usually visible on the outside of the air channel in the form of an aneurysm. The flexible nature permits the inspection of the air-channel as the air pressure migrates along the entire seam. If a defect is encountered, the inflation process will usually cease in the vicinity of the defect. This allows the entire length of field seam to be inspected and tested using the air-channel test procedure.

The project specifications initially re-quired destructive field-seam tests every 1,000 ft. (300m) of field seam, but allowed the destructive samples to be obtained from the anchor trench and not on the produc-tion liner based on successful air-channel test results. This destructive sampling is significantly less frequent than traditional destructive tests that are conducted every 500 lineal feet (150 lineal meters) of field PVC geomembrane seam. The elimina-tion of destructive samples from the pro-duction liner is noteworthy and should be adopted in other applications.

After the field seams are tested and approved, the integrity of the PVC geo-membrane was also tested using elec-trical leak-location methods (Photo 1,

page 26) to ensure the exposed geomem-brane is defect free to protect the pumped brine. Electrical leak-location methods are readily used for these geomembranes and can locate extremely small defects.

Figure 1 | Relationship between sheet temperature and required air-channel pressure to achieve seam peel strength of 2.6 N/mm (15 lbs./in.) from Stark et al. (2004)

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www.americanwick.com



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Chile Ponds

That is how we want our company

In manufacturing our productsWith our clients

With the environmentTransparent like water

SKAPS IndustriesSKAPS IndustriesSKAPS INDUSTRIES is the

leading manufacturer in the fi eld of

geosynthetics and offers wide array of

products for civil and environmental

applications in the U.S. and abroad.

We offer the following products:• Nonwoven Geotextile• Woven Geotextile• Drainage Geonet• Drainage Geocomposite

SKAPS Industries is committed to meet the supply

demands of the largest orders under most rigourous

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implementing stringent quality control measures;

and to ensure utmost customer satisfaction.

SKAPS IndustriesSKAPS Industries335 Athena Dr., Athens, GA 30601

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GeosyntheticLeader

GeosyntheticLeader

Summary The evaporation ponds in the Salar

de Atacama region in northern Chile are lined with PVC geomembranes and they have performed well in this harsh environment. In addition, the use of a geomembrane-facilitated installation of a liner system in this dry and windy environment has suceeded because of the reduction in field seams due to the use of prefabricated panels.

The use of dual-track, thermal-fusion welds to create the field seams facilitated testing of the entire length of the field seam and omission of destructive tests on the completed liner with air-channel testing. Further, the use of prefabricated panels and fewer field seams resulted in completing the liners quicker than using 7m-wide geomembrane sheets, and that expedited the initiation of the evaporation process and generation of revenue. An av-erage of 325,000 ft.2 (30,000m2) of PVC geomembrane was deployed, welded, and tested on a daily basis.

SQM’s Salar de Atacama evaporation ponds represent the largest PVC geomem-brane installation in the world to date with more than 16 million m2 of geomembrane installed and utilized since 1996.

AcknowledgmentsPVC manufacturer:

Canadian General-Tower Ltd.Panels fabricator and installer:

Solmax International Inc.QA/QC and electrical leak detection:

Solmers International Inc.

ReferencesASTM D 7177, 2005, “Standard test

method for air-channel testing of fi eld PVC Geomembrane Seams,” American Society for Testing and Materials, West Conshohocken, Pa., USA.

PVC Geomembrane Institute (PGI), 2004, “PVC Geomembrane Material Specifi cation 1104,” University of Illi-nois, Urbana, IL, www.pvcgeomem-brane.com, January 2004.

Stark, T.D., Choi, H., and Thomas, R.W., 2004, “Low Temperature Air Chan-nel Testing of Thermally Bonded PVC Seams,” Geosynthetics International Journal, Industrial Fabrics Associa-tion International (IFAI), Vol. 11, No. 6, December, pp. 481-490.

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http://www.skaps.com

http://www.pvcgeomem-brane.com

www.atarfil.com

Figure 1 | Locations of pre-installed current return electrodes (1 and 2). There was no sand over the geocomposite in the upper half of the cell.

| Ian D. Peggs, Ph.D., P.E., and president of I-Corp International Inc., is a member of the Geosynthetics Editorial Advisory Committee.

Liner integrity/leak-location survey: The significance of boundary conditionsBy Ian D. Peggs

IntroductionA geoelectric integrity survey was requested on a new land-

fill cell with the following lining system from the top down:• 18 in. sand• Geotextile/geonet/geotextile composite (geocomposite)• Primary geomembrane• Geosynthetic clay liner (GCL)• Geomembrane (rub sheet)• Geocomposite• Secondary geomembrane• Prepared subgradeThere was no sand above the primary geomembrane in half

of the cell, which was on a slope. There was a berm along the low edge, along with a sand layer below the primary GCL. It was determined that a successful survey could not be per-formed on this lining system.

Following are the detailed procedures taken to confirm that an effective survey could not be performed. These de-tails, in turn, identify some of the parameters that need to be considered, and actions that need to be implemented, during both the design and construction phases of a lining system to ensure that if a geoelectric survey is required, it can be satisfactorily performed.

For instance, while it makes technical sense to encapsulate a GCL, it may make it impossible to perform an electrical integrity survey because there must be sufficient moisture in the GCL and access to the GCL.

Basis of electrical surveysThe survey technique is based on the assumption that the

geomembrane is an electrical insulator. Consequently, the boundary conditions for a successful survey are as follows:

• A conductive medium above the geomembrane• A conductive medium through the holes being located• A conductive medium directly underneath the geomembrane• No electrical connection between the media above and

below the geomembrane other than through the holes to be located

An electric potential is applied between a current injector electrode placed in the medium above the geomembrane and a current return (ground) electrode in the medium below the liner. Current flows only through holes in the liner. A dipole (two-electrode) probe is then used to measure the potential gradients on the surface of the overlying medium (sand, in this case) and identifies the steep characteristic gradients associated with a leak.

An analogy is measuring the surface elevation gradients on pond water with a whirlpool at a large leak. Away from the whirlpool (leak), the gradient is essentially zero with a little background “noise” from ripples on the surface. As the dipole probe enters the whirlpool, the gradient increases to a maxi-mum when the leading electrode is directly above the leak (in the center of the whirlpool).

As the survey probe continues to move, the gradient be-comes zero when the probe electrodes are equidistant astride the hole. The gradient reaches another maximum, but of the opposite sign to the previous one, when the trailing electrode is over the hole. As the probe climbs out of the whirlpool, the gradient returns to the zero background level. This character-istic up/down/up signal can occur only at a hole. The survey identifies such signals and locates the center of the leak mid-way between the two peak signals.

Survey procedure and observationsIn a double lining system, the current return electrode is

usually placed down the side slope riser pipe into the second-

ary sump where it activates the conductive medium under the primary geomembrane. Thus, this conductive medium must be continuous from the secondary sump to wherever in the primary liner there might be a hole.

Since there was no secondary sump in the new cell, we previously arranged for two plate electrodes to be placed in contact with the GCL during construction of the lining system connected to wires that would exit the primary geomembrane in the anchor trench. The electrodes were placed halfway down the longer west slope ~180 ft. from each end of the ~750 ft.-long cell, shown here in Figure 1.


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Figure 3 | Location (5) of new current return electrode attached directly to the GCL.

To calibrate the equipment that would define the spacings of the orthogonal grid pattern used for surveying, a ~0.25-in.-diameter hole was made in the primary geomembrane at a location 250 ft. south—about halfway up the sand-covered area of the west slope, as shown in Figure 2. The origin of the coordinate grid was in the northeast (bottom right) corner of the cell. Damp sand was placed in the calibration hole, a little water was added, the geocomposite was replaced over the hole and wetted, and the sand cover was replaced to reproduce the condition of the original primary liner.

A potential of 250 VDC was applied between an electrode in the sand (see 4 in Figure 2) ~200 ft. to the south of the hole and the previously installed current return electrode to the south (1). A survey traverse was made for +/- 50 ft. in a north/south (left/right) direction directly over the calibration hole, but a characteristic leak signal was not obtained—the signal was constant. The applied potential was increased to 500 V, but still no leak signal was generated.

In both cases, the current registered on the power supply was a very low 1 mA (the lowest scale reading). Normally this would be in the region of 20 to 50 mA. For instance, in a survey on a 3-acre cell at another site during the previous two days the current was 35 mA at 450 VDC. A low current would typically indicate that there are no leaks in the liner, but it should still be possible to clearly “see” the calibration hole.

Discussions with site personnel revealed that the two cur-rent return plate electrodes had been installed with different types of cushion protection between the plate and the GCL. The southerly one was cushioned with geocomposite and the northerly plate was cushioned with GCL.

The former could insulate the GCL from the plate preclud-ing the required good electrical contact. To determine whether this was a factor in not “seeing” the calibration hole, the south electrode was disconnected and the connection was made to the north electrode. However, the resulting calibration traverse was again unsuccessful in indicating the leak.

Factors that could lead to the lack of a signal at the calibra-tion hole were considered:

1. Poor connections between current return plate electrodes and GCL

2. Insufficient conductivity within the GCL along the ben-tonite layer, which was too dry

3. Insufficient conductivity across the geocomposite The conductivity of the sand was not in question.

To address item 3, a water truck was used to soak the ex-posed geocomposite along the top edge of the sand so that the water would drain under the sand and wet the geocomposite above the hole. The leak still was not identified.

To address item 1, a long-strip electrode was clamped to the GCL through a hole made in the geomembrane about 50 ft. to the west of the calibration hole (Figure 3).

A strip of the GCL’s upper geotextile was cut and folded back to expose the bentonite powder over an area about 2 in. wide by 8 in. long. Strip electrodes were placed over the ben-tonite and under the GCL and clamped together at each end of the exposed strip. The assembly was wetted to assure good contact and good local conductivity. With an applied potential of 500 VDC, the current was still indicating 1 mA and the hole still was not seen when surveyed. This implied that the GCL was insufficiently conductive.

To further address this concern (item 2 above), a 500 VDC potential was applied between the strip electrode (5) and the north current return electrode (2) on the GCL, a distance of ~80 ft. Thus, current would flow only through the GCL. The power supply still showed a current of only 1 mA. To ensure that the ammeter on the power supply was functioning correctly, the current was measured with a multimeter on the microamp scale. As should have occurred, the current did increase with applied potential but reached only about 6 A at 500 VDC. This very low current clearly confirmed that the GCL was insufficiently conductive.

Further discussions revealed that the primary geomembrane over the east berm was constructed with sand underneath the GCL. Therefore, the GCL may have extracted moisture from the sand to make it adequately conductive, to the extent that it may be possible to survey the complete berm geo-membrane and the associated pipe penetration boots. This was attempted.

Another calibration hole was placed in the primary geo-membrane about 75 ft. to the south of the previous calibration hole (3), and halfway up the west side of the berm, as shown in Figure 4 (6). The GCL below the hole was not wetted and the hole was filled with damp sand. The geocomposite was placed back over the hole but was not wetted. Sand was replaced over the geocomposite and compacted by foot. Thus, the lining system over the calibration hole was in the same condition as the rest of the primary liner over the rest of the berm.



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Figure 2 | Locations of calibration hole (3) and injector electrode (4).

Case History

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The injector electrode (7 in Figure

4) was placed on the sand cover about 100 ft. to the south of the calibration hole. The current return electrode (8 in Figure 4) was placed in the sand under the geomembrane (through a hole in the geomembrane) adjacent to the injector electrode. At 500 VDC, the current flow remained at the 1 mA reading and the calibration hole again could not be seen. Therefore the GCL had not absorbed sufficient moisture from the underlying sand to make it conductive.

The berm calibration hole (6) was un-covered and water was poured through the hole to wet the GCL. The underside of the geocomposite was wetted, placed over the hole, and the top of the geo-composite was thoroughly wetted. The sand was replaced and foot-compacted. At an applied potential of 500 VDC, the current flow increased to 11 mA. A detailed survey traverse was made for ±10 ft. across the calibration hole.

As shown in Figure 5, the up/down/up characteristic leak signal was ob-

tained, but it was not very large. The signal due to the hole became signifi-cant only about 2 ft from the hole. On the positive potential side of the hole, the measured peak voltage (48 mV) barely exceeds three times the back-ground signal (~15 mV) as required by ASTM D7002, “Standard Practice for Electrical Methods for Locating Leaks in Geomembranes Covered with Water or Earth Materials.”

Figure 4 | Locations of berm calibration hole (6), berm injector electrode (7), and berm current return electrode (8).

Figure 5 | Characteristic leak signal across berm calibration hole.

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Case History

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DiscussionThe calibration surveys and test

measurements showed that the GCL under the primary geomembrane did not have the required conductivity to complete an electrical circuit between a hole in the primary geomembrane and the current return electrode attached to the GCL some distance away from the hole. Even where the GCL was under-laid with sand on the berm, there was insufficient moisture in the benton-ite of the GCL to make it conductive. Thus, it was not possible to perform an electrical integrity survey on the pri-mary geomembrane.

As demonstrated, it would be neces-sary to wet and hydrate the GCL under the geomembrane and to wet the geo-composite above the geomembrane in order to perform an effective survey. The latter can be done by rain or by using a water truck, but the former cannot be done without removing and reinstalling the geomembrane.

While wetting the geocomposite and the liner from above will cause some water to penetrate any leaks, the area of wetted GCL will remain very small (only at the leaks). While this will provide a conductive path through the GCL to the sand, it may or may not be sufficient to provide an adequate signal during a sub-sequent survey—the current flow is a function of the cross-sectional area of the wetted path. Previous surveys with only a geocomposite between primary and secondary geomembranes have proven that one cannot rely on the leaking water to provide an adequately conductive path-way under the primary geomembrane.

In this case, it certainly will not be ad-equate in the areas where the liner is not underlain by sand. Therefore, for an effec-tive survey the complete GCL should be uniformly wetted. This is impractical after construction. During construction, how-ever, as has frequently been done, the GCL could be irrigated with about four passes of a water spray just before the geomembrane is placed. Similarly, a new geocomposite primary leachate collection layer can be wetted before a sand cover is placed over it. However, geocomposites are rarely a problem after they have been soaked for some time with leachate in service.

Alternative methods for leak detection

There are few other options for locat-ing leaks in the primary geomembrane. Blowing smoke between the liners and observing where it rises out of the geo-membrane has been attempted, but not very successfully—one can never be sure

just how far the smoke penetrates under the geomembrane.

Pulling a vacuum on the leak-detection system and using a sensitive microphone above the liner to listen for the noise of air being drawn into a leak has also been done. However, since this cell is connected to adjacent lining systems, the volume to evacuate would be unmanageable.

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When water is actively passing through a leak and draining through a mineral layer under the geomembrane, a measur-able potential low can be generated at the entrance to the leak flow channel. But the topography of this cell would not allow it to be flooded to generate active leaks. This approach would only work where there is sand under the GCL.

Perhaps the method with the most po-tential for success in this case would have been to insert a lighter-than-air tracer gas along the secondary leachate collection pipe and to monitor its emission through any leaks in the liner using a sensitive gas analyzer. This is done very effectively on landfill caps with the readily avail-able methane and carbon dioxide gases. It would probably be necessary to pass the tracer gas through a long hose previously inserted in the LDS pipe. The hose would be drawn along the pipe as the survey is performed above the liner and above the location of the end of the hose where the gas is emitted. The holes that are presently in the liner could be used for calibration purposes and to assess the feasibility of such an approach.

SummaryIn preparing for a conventional geo-

electric-applied potential liner integrity survey as the final stage of liner instal-lation CQA, it was found (as the result of several different calibration attempts) that an effective survey could not be per-formed on the primary liner. The GCL under the geomembrane was not ade-quately conductive.

Calibration could be successfully achieved only where the GCL was un-derlain by sand, and then only by thor-oughly wetting the GCL through the hole and by wetting the overlying geo-composite. It would not be practi-cal to wet the complete GCL as would likely be required where it is underlain by sand, and as would be essential where it is placed on the 30-mil-thick “rub” sheet.

This survey demonstrates the need to consider the structural requirements for an effective geoelectric liner-integrity survey during the design and construction phases of the lining system. Plan ahead with the four boundary conditions in mind.

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| Letters to the editor |

Introductory note from the letter writer: Geosynthetics

editor, Ron Bygness, originally invited an article from me on

the first GRS wall with negative batter in New Zealand. In

order to explain why the Kiwis were different, I found it nec-

essary to comment on why the U.S. is so far behind in GRS

technologies. Ron and I agreed that my submission would be

better served in a letter to the editor, where I would be allowed

more latitude in opinion.Al Ruckman and I own Soil Nail Launcher, Inc., a design/

build geotechnical firm that specializes in soil and rock rein-

forcement. The Web site is www.soilnaillauncher.com. Al and

I have been involved in reinforced soil research since 1971.

I was also chair of the TRB Committee on Geosynthet-

ics, 1990-1997; and chair of NCHRP 12-59, Design and

Construction Guidelines for Geosynthetically Reinforced

Soil Abutments. The first publication from that effort is the

landmark NCHRP Report 556 (2006).

To the editor:The first GRS wall built in New Zealand leans outward

and on purpose. GRS is the acronym for geosynthetically

reinforced soil with generic components. The Kiwis are

noted for punching above their weight, thus this was the

right crowd for plunging into the deep end first.

Introduction of generic GRS technologies in New

Zealand was part of the landslide control portfolio with

launched soil nails. These innovative tensile inclusions create

their own brand of reinforced soil in in-situ soils. However

there are instances where lost soils must be replaced. A

case in point would be on highways where the sliding has

regressed into the traveled way. Horizontally launched nails and vertically launched mi-

cropiles can be tied together in a concrete frame to create

a platform on which to construct a retaining wall. All this

modern reincarnation of classic foundation engineering

| Geosynthetically reinforced soil wall with negative batter built by Hiway Stabilizers of New Zealand.

Photos provided by Bob B

arrett

Retaining-wall dialog: ‘A tale of two walls‘

By Bob Barrett

0806GS_cv1-p21.indd Sec1:6


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| Letters to the editor |

elements is then combined with GRS to restore a gap in the

roadway. Negative batter adds width to the final platform.

The engineers of Hiway Stabilizers incorporated all of this on

their first landslide remediation project in New Zealand.

Some background on how they jumped ahead of the

world to get to this level:GRS technologies have a tattered history. Modern

geosynthetics are only a generation old. (As long as Al

Ruckman, Bob Holtz, Jonathan Wu, Bob Koerner, Barry

Christopher, Jim Collin, Richard Bathurst and I are still

around—otherwise it will be two generations.)

These new polymers have, as Geosynthetics readers know,

made a dramatic indentation into the practice of geotechni-

cal engineering. This indentation has yet to reach the ap-

propriate depth on the structural engineering community.

There was a group of dedicated researchers in the 1970s

and ’80s whose mission was to decipher the code for how

geosynthetic inclusions in compacted soil created a com-

posite that behaved differently than the two elements that

comprise that composite. Evolving at a more rapid rate

were our wonderful capitalist interests. These folks with

their proprietary offerings soon subverted the quest for

absolute truth.Instead of bringing the civil engineering community

into the learning and growth process, the commercial sec-

tor offered an easy way out. No need to learn all that soil

mechanics stuff. No one needs to know anything more than

what the vendors and vendor associations provide. Our

government agency engineers bought into this concept. And therefore, hardly anyone in the United States can properly design poly-merically reinforced soil features. It is a level of sloth that de-fies explanation.This was all ex-plained to the bright-est of the soil and structural engineers of New Zealand. They could see that

it was important to learn the simple design criteria of ge-

neric reinforced soil technology. The alternative was to sit

back and let vendors and structural engineering associations

dictate what could and could not be done.Certainly the quasi-tieback vendor offerings could not

tolerate reverse batter. After seeing their miserable failures in the 1999 Chichi

earthquake and in the recent feature in Geosynthetics

(“Eight ways to achieve improved retaining-wall perfor-

mance” By Michael R. Simac, April/May, pp. 30-36), we

come to realize how large our mistake was to rely on vendor

designs for the last two decades. We can begin to see how

much our sloth has cost.Not so with the Kiwis. They quickly understood and as-

similated what has taken 40 years and tens of millions of tax

dollars to learn. To wit: Spacing is more important than the

strength of the inclusion. Colorado DOT built a full-scale

bridge pier with bed linen to demonstrate this.

Creep is not possible in compacted granular soil when

the inclusion spacing is close (8-12 inches). This enlightened

finding has been demonstrated with Colorado DOT and

U.S. Forest Service funds at the University of Colorado/

Denver and at the FHWA research facility in McLean, Va.

It has been confirmed in hundreds of constructions under

the seal of Albert Ruckman. As shown in the bedsheet demo and in field construc-

tions, in-air stiffness of the reinforcement is not necessary

| Dr. Nelson Chou (center) inspecting a typical failure with widely

spaced reinforcements in seismic events (in this case, the Chichi

earthquake in Taiwan, 1999).This MSE wall failed in that earthquake in Taiwan. It illustrates

the vulnerability of some versions of AASHTO/FHWA/NCMA

sanctioned designs for MSE walls. This wall had stiff, widely

spaced reinforcements. As shown in the article in Geosynthetics

(April-May, pp. 30-36, “Eight ways to achieve improved retain-

ing-wall performance”), this quasi-tieback philosophy for design

has produced many failures and is inferior to weaker reinforce-

ments on close spacing. There are no known failures with GRS

walls with CMU facing designed as per our guidelines.

0806GS_cv1-p21.indd Sec1:7

7/26/06 9:24:59 A

0207GS_26_45.indd 38 1/8/07 1:42:21 PM




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Larger panels decreaseinstallation costs.

Factory seams decreasefield seam problems.

• Daily and Temporary Landfill Covers

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| Barry Christopher is an independent geotechnical engineering consultant specializing in reinforced soil

and other ground improvement technologies. He has authored numerous technical papers including design

manuals for the U.S. Federal Highway Administration (FHWA).

Junction-strength requirements for roadway design, construction By Barry R. Christopher

IntroductionCurrently many engineers are confused about junction-

strength requirements for geogrids used in roadway base rein-forcement and subgrade stabilization applications, primarily because of commercialism of junction strength requirements. Some promotional efforts recommend relatively high junction strength, while others dismiss junction strength altogether.

Confusing?At least one local public agency specifies a junction strength

for one type of geogrid and states that it is not required for another type. Adding to the confusion are the methods of re-porting junction strength.

Junction strength is usually defined in terms of the ultimate junction strength (i.e., the force required to rip the junction apart), as measured by the Geosynthetics Research Institute GRI GG2 procedure.

However, junction strength is also often reported in terms of force per width of the material, which is obtained by divid-ing the force applied to the junction by the nominal aperture opening, or efficiency, which is the ultimate junction strength divided by the strength of the rib.

Regardless of which definition is used, the specification of ultimate junction strength is applicable in relation to quality control and meeting minimum constructability requirements.

Pavement performance is evaluated based on serviceability (i.e., permanent deformation, a.k.a. rutting, over the life of the pavement) as opposed to a failure state and, correspondingly, the low-strain modulus of the geogrid is most important for reinforced base applications. Junctions are required to provide geogrid interaction at these low strains and, thus, junction stiff-ness or modulus is required for design.

The stiffness of the junction is related to the ability of the junction to transfer stress at low strains. However, the junction stiffness requirements have not been defined and a test method is not available that allows for an evaluation of junction stress-strain characteristics.

While the ultimate junction strength is not necessarily re-lated to its junction stiffness, it is related to construction sur-vivability (i.e., the ability to resist orthogonal ribs from being ripped off of the geogrid during construction). The key issue is: How strong does the junction need to be (and the geogrid material, for that matter) to survive the level or harshness of the anticipated construction activities?

Relatively low strength junctions are typically required to survive construction (GMA, 1998). In pavement test sec-tions reported in the literature (e.g., see references reviewed in GMA, 1998 and Berg et.al., 2000), several of which have been observed by the authors, geogrid junction failure has not been reported during exhumation of the geogrid following traffic loading. However, there have been reports of junction failures during construction (although the conditions resulting in these problems have not been well documented) and it is still prudent to specify minimum construction survivability junction strength for quality control and to preclude junction failure during adverse construction conditions.

The correct technical approach is to base junction strength on: (1) Design requirements in terms of stiffness at working loads pertinent to the permanent strain levels expected in the reinforcement; (2) Construction requirements in terms of strength required to survive the anticipated construction condi-tions; and (3) Requirements that the rib transverse to the load is challenged through its junction strength.

This paper provides a review of technical literature to es-tablish those requirements. Based on this review, recommen-dations are provided to establish sound and reliable minimum requirements based on field trials and research, as outlined in the paper.

Adding to the confusion are the methods of reporting junction strength.

The key issue is: How strong does the junction need to be (and the geogrid, for that matter) to survive the level or harshness of the anticipated construction activities?


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Junction strength for constructionJunction strength for roadway construction is essentially

the minimum strength required to maintain the integrity of the geogrid during shipment and placement. During roadway construction operations, the geogrid experiences relatively high levels of localized load as aggregate material is placed, spread, and compacted on top of the reinforcement.

During placement, the aggregate pushes down on the geogrid (providing confinement) and out (developing interlock, which is key to its performance). Provided proper construction techniques are used, some level of aggregate cover will be maintained on the geogrid during construction, meaning the junctions of the geogrid are under a state of confinement due to the aggregate.

For construction, the junction strength specification is typically and appropriately based on the standard junction strength quality control test, Geosynthetics Research Institute GRI GG2. For example, the American Association of State and Transportation Officials (AASHTO) references this test in AASHTO 4E-SR “Standard of Practice Guidelines for Base Reinforcement.”

The GRI-GG2 test procedure involves gripping the cross member of a geogrid rib on both sides of the junction with a clamping device and gripping the other end of the geogrid rib (i.e., in the principal loading direction) with another clamp. Load is applied to the two clamps until rupture of the junction occurs. Depending on how the gap between the clamps (i.e., over the junction) is machined, the junction may experience a restricted to small amount of out-of-plane rotation and peeling during loading.

Grab tests involving peeling of the junction (either by ma-chine or hand) should not be performed, as these tests allow for unrestricted out-of-plane rotation without any constraint of the junction and, thus, do not represent conditions seen in the field. Recommended values for construction survivability based on performing tests using GRI-GG2 are reported in the literature. Based on a literature review of 19 geogrid studies involving installation survivability, the Geosynthetic Materials Associa-tion (GMA) recommends a minimum junction value of only 35N (8 lbs.) for construction, as obtained from the GRI-GG2 test (GMA White Paper 1).

Conversation with several state agencies indicated that they have increased this value to 110N (25 lbs.), based on their own experience with construction that was more ag-gressive than anticipated. Other state and local agencies have specified even higher values, on the order of 270N (60 lbs.) or more, based on specific products and reportedly due to

junction problems with other products (albeit, with anecdotal background and no reported conditions, e.g., aggregate type, truck loading, lift thickness, subgrade strength, etc., that resulted in these problems).

Considering the number of agencies specifying a junc-tion-strength requirement and the order of magnitude range of requirements specified, it would appear that an unbiased, minimum value (similar to construction requirements for geo-textiles) should be established to assure that junctions are not ripped off during construction and for quality control.

A conservative value should be developed by the industry that will allow products to be used in any application without concern. On projects where construction is not anticipated to be severe, or on projects where field trials and monitoring can be performed, leeway should be given to using products with lower junction strengths, as is currently done for geotextiles in AASHTO M288-05 (AASHTO, 2005).

… it would appear that an unbiased,minimum value should be establishedto assure that junctions are not ripped off during construction and for quality control.



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Requirements

The junction integrity can, and should, be evaluated through instal-lation damage assessment tests, using the procedure in ASTM D 5818 “Stan-dard Practice for Obtaining Samples of Geosynthetics from a Test Section for Assessment of Installation Damage” and performed by an independent labo-ratory (as routinely performed for other geosynthetic reinforcement applica-tions). Installation damage assessment tests are field trials conducted with sim-ulated field conditions (e.g., granular base materials placed over the geogrid and trafficked by placement and com-paction equipment).

A concise sampling and testing re-gime is used to obtain reduction fac-tors for design properties of interest (e.g., design strength and, in this case, junction strength and integrity). Both strength reduction factors and any junction failures that occur during the test should be reported, such that the design engineer can assess the suit-ability of the geogrid for the specific application conditions.

An alternative to relying on tests is to have the contractor construct a “test pad” to demonstrate that the placement technique does not damage the geosyn-thetics as recommended by the FHWA

Geosynthetic Design and Construction Guidelines (Holtz et. al., 1998).

Junction strength design requirements

Junction requirements for actual per-formance of the geogrid in roadways are currently under evaluation by a number of researchers, and, as of today, stan-dard requirements have not been clearly established (other than through product specific empirical based designs). During the operational life of the roadway, the geogrid experiences relatively small lev-els of dynamic load from traffic. These loads result in dynamic strains, which accumulate and thus result in a perma-nent strain in the geogrid with increasing traffic levels.

The accumulated in-service tensile strain in the geogrid has been measured in laboratory and full-scale model stud-ies at a maximum of approximately 2% (Berg et.al., 2000), and is consis-tent with field measurements in roads. The strength of the reinforcement at 2% strain (i.e., the 2% secant modulus) is also often specified as a design strength value for the geogrid (Berg et.al., 2000 and AASHTO 4E). Therefore, Kupec et. al. (2004) argued that the strength at 2% strain should also be the basis for the junction strength.

Considering that the soil interaction with the junction results in the stress in the geogrid, this would appear to be a logical argument. But a standardized test to evaluate the junction modulus does not exist. The current junction-strength test (GRI GG2) does not provide a method to evaluate the stress-strain characteristics of a junction.

In addition, the conventional test does not provide confinement on the junction and, to the contrary, allows the junction to rotate and thus sets up a peeling type failure in biplanar products (e.g., woven and welded geogrids). In the application, the roadway layers (ag-gregate and asphalt concrete) above the geogrid provide a level of confinement to the geogrid junctions as these loads are applied and the failure is more of a shear mode.

Kupec et.al. (2004) modified the ex-isting GRI GG2 test with a special set

0207GS_26_45.indd 42 1/8/07 1:42:29 PM


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Requirements

of clamps that did not allow rotation of the junction and compared the strength obtained at the failure of the junction to the strength at the 2% strain value in the geogrid. However, it could be argued that the junction strength value should be based on junction strength required to achieve a 2% strain in the geogrid.

Indeed, if the junction must trans-fer the load to the geogrid, the junction strength at 2% strain may also be an ap-propriate value for design. This assumes that the junction is more flexible than the geogrid and, thus, eliminates the influ-ence that the junction itself has on the strain in the geosynthetic. Therefore, the influence of the junction on the geogrid modulus should also be evaluated.

Optimally, a test should measure the strain in the junction and the rib, to ob-tain a 2% strain value resulting from both deformation of the junction and strain in the rib to which the stress is being transferred. Rotational stiffness is often quoted as a method to demonstrate

the stiffness of the junction. While in-plane stiffness may be important, the test method does not provide a direct junc-tion strength or modulus value.

A test is required that will evaluate the stress that can be transferred by the junction to the ribs in the geogrid at a design strain value (e.g., 2%). The test

should simulate field conditions and either minimize out-of-plane rotation or even evalu-ate direct shear of the junction. To modify

the existing junction strength tests or de-velop a new test, the in-soil performance of the junctions should be evaluated for direct comparison or even be directly used for the design value if correla-tions with a simple lab index test cannot be established.

A pullout test has been suggested as a method to simulate the ultimate shear that develops when a wheel pulls on the restraining geogrid (lo-cated adjacent to the wheel, Perkins et.al., 2004). By using the modified pullout procedure recommended by Perkins et.al.(2004) for pavement ap-plications and instrument the geogrid to evaluate the characteristics of the

junction, this method could be used to determine the in-soil response of the junction to in-plane loading and provide the basis for comparison with simplified lab tests. This procedure is currently under evaluation by ASTM Committee D35.

RecommendationsIn the interim, the following approach

is recommended:1. Use a conservative minimum

junction strength that should be estab-lished industry-wide through data from full-scale installation damage tests in accordance with ASTM D 5818 and documenting the integrity of junctions. For soft-soil applications, a minimum of 150mm (6 in.) of cover aggregate shall be placed over the geogrid and a loaded dump truck used to traverse the section a minimum number of passes to achieve 100mm (4 in.) of rutting. A photographic record of the geogrid after exhumation shall be pro-vided, which clearly shows that junc-tions have not been displaced or oth-erwise damaged during the installation process. This information will allow the establishment of junction surviv-ability requirements in the future for the range of geogrid materials. (This was essentially the method used to establish the minimum survivability requirements for geotextiles in AAS-HTO M288-05.

2. For empirical methods, junc-tion strength is not related to design but only to the characteristics of the geogrid(s) used in the laboratory or field trials to establish the traffic benefit ratio. Alternatively, continue the proprietary practice based on field trials, experience and product-specific data.

3. For mechanistic-empirical design, see Perkins et. al. (2004) for a discus-sion of design input values and sup-port research to calibrate these input requirements.

4. Continue to use geogrids with confidence that most any geogrid will provide some level of improved performance; albeit not necessarily the optimum.

But a standardized test to evaluate the junction modulus does not exist.

0207GS_26_45.indd 44 1/8/07 1:42:36 PM




arch 2007

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ReferencesAASHTO (2005) Standard Specifi ca-

tions for Transportation Materials and Methods of Sampling and Test-ing (25th ed.), American Association of State Highway and Transportation Offi cials, Washington, D.C.

AASHTO (2005) Standard Specifi cations for Geotextiles—M 288, Standard Specifi cations for Transportation Ma-terials and Methods of Sampling and Testing (25th ed.), American Associa-tion of State Highway and Transporta-tion Offi cials, Washington, D.C.

ASTM D 5818 (2004) “Standard Prac-tice for Obtaining Samples of Geo-synthetics from a Test Section for Assessment of Installation Damage”, Annual Book of ASTM Standards, Section 4, Construction, Volume 04.13 Geosynthetics, ASTM Interna-tional, West Conshohocken, Pa.

Berg, R.R., Christopher, B.R. and Perkins, S. (2000) “Geosynthetic Reinforcement of the Aggregate Base/Subbase Courses of Pavement Structures,” prepared for American Association of Highway and Trans-portation Offi cials Committee 4E, prepared by the Geosynthetic Mate-rials Association (GMA), 176 p.

Geosynthetics Research Institute (2005) GRI Test Method GG2 “Indi-vidual Geogrid Junction Strength”, Geosynthetic Research Institute, Folsom, Pa. (http://www.geosyn-thetic-institute.org).

GMA (1998) White Paper 1: “Geosyn-thetics in Pavement Systems Ap-plications—Section One: Geogrids; and Section Two: Geotextiles,” pre-pared for AASHTO by the Geosyn-thetic Materials Association (for-merly the IFAI Geotextile Division), www.gmanow.com

Perkins, S.W., Christopher, B.R., Cuelho, E.L., Eiksund, G.R., Hoff, I., Schwartz, C.W., Svanø, G. and Watn, A, (2004) “Development of Design Methods for Geosynthetic Rein-forced Flexible Pavements,” report prepared for the U.S. Department of Transportation Federal Highway Administration, Washington, D.C., FHWA Report Reference Number DTFH61-01-X-00068, 263p.

Kupec, J., McGown, A. and Ruiken, A. (2004) “Junction Strength Testing for Geogrids,” Proceedings of the Con-ference EuroGeo 2004, Munich, Ger-many, pp. 717-722.

0207GS_26_45.indd 45 1/8/07 1:42:37 PM

http://www.srwproducts.com


http://www.geosyn-thetic-institute.org

http://www.gmanow.com

www.leister.com

| Geosynthetic Institute |


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EnvironmentalProtection Systems

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Overview of GSI’s surveysBy Bob Koerner

| Geosynthetic Institute, 475 Kedron Ave., Folsom, PA 19033-1208 USA; +1 610 522 8440;

Fax 610 522 8441; E-mail [email protected]

It appears to this writer that any forward looking decisions—business or otherwise—should be made on the basis of factual information from the past. My son sent an E-mail to me stating: “Without data, yours is just an-other opinion!”

One step further in gathering this data is that the information is obtained via surveys. This brief note presents our past and ongoing surveys, all of which emphasize the use (or nonuse) of geo-synthetic materials.

Liners and covers

In the landfill liner and cover area, we conducted our first survey of U.S. State Environmental Protection Agency regu-lations in 1993 (GRI Report #11). This was followed by two subsequent paral-lel surveys, one in 1998 (GRI Report #21) of U.S. states and the other in 1999 (GRI Report #23) of national regulations worldwide. This dual reporting of U.S. state regulations and worldwide country regulations is currently being updated by Jamie Koerner, with reports due in early 2007.

Roadways

In the highway/transportation area, we conducted our first survey on be-half of the Federal Highway Adminis-tration in 1989. This was followed by a survey in 1992 (GRI Report #7) on state-by-state specifications on using geotextiles in separation, reinforcement, filtration, drainage, paving fabrics, and silt fences.

Our most-recent survey in 2006 (GRI Report #31) tracked the adoption and use of the AASHTO M288-05 specification among the 50 state highway departments in the United States.

Somewhat related in this general category was our survey of retaining

wall costs in 1998 (GRI Report #20). The result of this survey indicated that geosynthetically reinforced retaining walls are the least costly of all retain-ing wall systems (gravity, crib/bin, metallic-reinforced, and geosynthetic-reinforced). This was our most widely used and referenced report, at least to our knowledge.

Materials

Regarding geosynthetic material quantity usage, we have conducted HDPE and LLDPE geomembrane sur-veys annually from 1998 to 2004, and geonet/geocomposite surveys annually from 1999 to 2004. These product usage surveys, however, are best obtained and conducted by the Geosynthetic Materials Association (GMA) and their efforts in this regard are ongoing.

Coming up

Our next surveys will focus on as-sessing geosynthetic usage and/or regu-lations in large-scale agriculture and aquaculture businesses. (Note that these particular topics will be the focus of the GRI-21 Conference at GeoAmericas in Cancun, Mexico, in March of 2008.) Of course, federal, state, and regional regu-lations will be an integral part of these future surveys.

In closing, the GRI reports noted above are available free for members and associate members, and for a nominal charge for non-members. Please contact us for more information.

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http://www.ages-corp.com


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| Panorama |

GEO news and notes from around the world

GMA-Mexico offers classes

The Mexico office of the Geosyn-thetic Materials Association designed and delivered two courses last fall. One was for the Mexican Army’s Departa-ment of Engineering; the other with open enrollment for civilian engineers and academics.

The military engineers were very re-ceptive last September to see new materi-als and tools to use in finding solutions in their jobs, said Oscar Couttolenc of GMA-Mexico. They even asked me if we could organize a second course, focusing the topics on designing with geosynthet-ics, once they already know the main applications and products, he said.

The second course in Mexico was held last November at the Universidad de las Americas in the state of Puebla.

“Geosynthetic materials and their ap-plications in civil engineering” was a two-day class. Its objective was to in-form and update civil engineers, espe-cially those working in geotechnical, hydraulics, and environmental areas, Couttolenc said.

The class emphasized technological advances, construction procedures, de-signing criteria, and current applications of geosynthetic materials used as a con-fident instrument in construction and maintenance .

There were 42 participants in this class, including 30% students, 30% professors, and 40% civil engineers from private companies and government offices.

Mountain route flowing now

Traffic on Highway 330 through California’s San Bernardino Mountains returned to near normal last fall after CalTrans reopened the route to motor-ists following three months of detours and closures.

The route between Highland and Run-ning Springs had been closed off and on while a $7.5 million slope stabilization project in two locations was completed.

Two primary components of the proj-ect were a 25-ft.-high rock wall, con-structed with the help of 4-ton boul-ders, and a 150-ft. embankment with a geogrid/geotextile covering below the highway. This cover plus the curving embankment redirect water below the roadway, while the rock wall at the bot-tom prevents erosion, said a CalTrans representative.

New officers for ASCEThe American Society of Civil En-

gineers (ASCE) installed newly elected officers to its board last October.

The new board representatives include:• William F. Marcuson III, Ph.D., P.E.,

Hon.M.ASCE, director emeritus of the Geotechnical Laboratory at the Water-ways Experiment Station in Vicksburg, Miss., was installed as ASCE president.

• David G. Mongan, P.E., F.ASCE, president of Whitney, Bailey, Cox & Magnani, LLC in Baltimore, Md., was installed as president-elect of ASCE. Mongan will assume the role of board president in the fall of 2008.

• Thomas R. Walther, P.E., F.ASCE, highway commissioner for Eau Claire County, Wis., will represent Sections and Branches in Region 3.

Region 4 Robert I. Smith II, deputy director of logistics and engineering at Fort Jackson in South Carolina, will represent Sections and Branches in Region 4

• Thomas M. Rachford, Ph.D., P.E., F.ASCE, vice president and corporate quality officer at Gannett Fleming En-gineers and Planners in Camp Hill, Pa., will represent ASCE’s seven Insti-tutes (Architectural Engineering Institute (AEI), Coasts, Oceans, Ports and Rivers Institute (COPRI), Construction Insti-tute (CI), Environmental & Water Re-sources Institute (EWRI), Geo-Institute (GI), Transportation & Development Institute (T&DI) and Structural Engi-neering Institute (SEI)).

• Eriks V. Ludins, P.E., a member of the Bridge Engineering Division of the city of St. Paul Public Works Department

in St. Paul, Minn., will represent Sec-tions and Branches in Region 3.

• Findlay G. Edwards, Ph.D., P.E., associate professor at the University of Arkansas in Fayetteville, and David F. Garber, P.E., P.L.S., F.ASCE, presi-dent of Garber-Chilton Engineers and Land Surveyors Inc. in LaGrange, Ky., will represent Sections and Branches in Region 4.

• Jack Furlong, P.E., project manager with Halff Associates Inc. in Dallas, and Jeanette Walther, P.E., P.T.O.E., traf-fic and transportation project manager at Bohannan Huston Inc. in Albuquer-que, N.M., will represent Sections and Branches in Region 6.

• Michael J. Barton, P.E., P.T.O.E., senior traffic engineer at Henningson, Durham and Richardson Inc. in Tuc-son, and Robert J. Russell, P.E., M.B.A., F.ASCE, engineering director at the Northern Nevada Regional Transporta-tion Commission in Reno, will represent Sections and Branches in Region 8.

• Mark Creveling, P.E., CEO of Simon Wong Engineering in San Diego, will represent Sections and Branches in Region 9.

Founded in 1852, ASCE represents more than 140,000 civil engineers world-wide and is America’s oldest national engineering society. For more informa-tion, visit www.asce.org.

ECTC’s updated technical manual now available

A revised and updated guidance docu-ment by the Erosion Control Technology Council (ECTC) is now ready for indus-try professionals.

Titled “A Technical Guidance Man-ual: Terminology, Index & Performance Testing Procedures for Rolled Erosion Control Products,” can be found on ECTC’s Web site, www.ectc.org under the “Testing” category in the “Docu-ments & Tools” section.

The document was originally de-veloped by the ECTC to aid in the un-



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http://www.asce.org

http://www.ectc.org


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derstanding and use of the most recent terminology, index/physical property test methods, and performance research for RECPs. It also was intended to as-sist engineers, geologists, soil scientists, landscape architects, contractors, and research facilities within the erosion con-trol industry in the selection of RECPs. The new document continues with these efforts and includes bench scale testing information. It also contains updates to all ASTM standards to reflect the current state of practice.

For more information about ECTC or the updated guidance document, contact Laurie Honnigford at +1-651-554-1895, E-mail [email protected], or visit www.ectc.org.

Pinning milfoil to the mat

The latest effort to foil further growth of milfoil on a pond in Litchfield, Maine, has taken the form of layers of black, geotextile mats.

A diver has placed the mats like carpet on the bottom of Upper Pleasant Pond in an area where a group of variable-leaf water milfoil plants was already marked off by buoys. The mats are made of a geo-textile fabric and are held down by rein-forcing rods that are placed into sleeves.

Plants under the mat die from lack of sunlight and slits in the fabric allow gases from decay to escape to the surface.

The plan is to also install mats near a public boat landing this spring to other sites if they prove successful.

Membrane seams addressed in new ASTM standard

The increased use of geomembranes as barrier materials to restrict liquid mi-gration created a need for a test method to evaluate the quality of geomembrane seams produced by tape methods.

ASTM International Committee D35 on Geosynthetics has met this need with the approval of the new standard

D 7272, Test Method for Determining the Integrity of Seams Used in Joining Geomembranes by Pre-manufactured Taped Methods. The standard is under the jurisdiction of Subcommittee D35.10 on Geomembranes.

Jeff PanKonie, senior sales engi-neer for Firestone Specialty Products, noted that the new Test Method D 7272 more accurately addresses the unique characteristics of taped seams. He added that D 7272 will become a refer-ence for engineers designing projects with taped seams, as well as for con-tractors who can use the standard for field testing.

Test Method D 7272 was developed to be used with most taped seams, whether the membrane is reinforced or nonrein-forced. The standard also has allowances for seam width, since seams can vary greatly with taped products dependent on the manufacturer and the types of membrane and taped seam.

Interested parties are invited to par-ticipate in the standards developing ac-

| The Reference Section |

Rock Slope Engineering Civil & MiningItem #22104(12/2004, soft cover, 431 pages)This extensively updated version of the classic text, Rock Slope Engineering by Hoek and Bray, deals comprehensively with the investigation, design and operation of rock s lopes. Invest igat ion methods include the collection and interpretation of geological and

groundwater data, and determination of rock strength properties, including the Hoek Brown rock mass strength criterion. Slope design methods include the theoretical basis for the design of plane, wedge, circular and toppling failures, and design charts are provided to enable rapid checks of stability to be carried out. New material contained in this book includes the latest developments in earthquake engineering related to slope stability, probabilistic analysis, numerical analysis, blasting, slope movement monitoring and stabilization methods.

To order, visit www.geosyntheticsbookstore.com; call 800 207 0729, +1 651 225 6913; or e-mail [email protected]

Barrier Systems for Waste Disposal FacilitiesItem # 22105(8/2004, hardcover, 600 pages) This book deals with the design of “barrier systems” which separate waste from the surrounding environment and which are intended to prevent contamination of both groundwater and surface waters. The authors discuss all key aspects of the

design of barrier systems, including leachate collection, natural barriers such as clayey aquitards, clay liners, geomembrane and composite liners, providing a state-of-the-art work of reference of great value to engineers and environmentalists alike. This retitled second edition of Clayey Barrier Systems for Waste Disposal has been fully revised and updated, with new chapters on geomembranes and geosynthetic clay liners as well as a number of new chapters.

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| Panorama |

tivities of Subcommittee D35.10. ASTM International standards are available for purchase from Customer Service (phone: 610/832-9585; [email protected]) or at www.astm.org.

For further technical information, contact Jeff PanKonie, Firestone Spe-cialty Products, Indianapolis, Ind. (phone: 317/575-7238; [email protected]).

Committee D35 meets Jan. 31-Feb. 2, 2007, at the January Committee Week in Costa Mesa, Calif. For membership or meeting information, contact Christine Sierk, manager, Technical Committee Op-erations, ASTM International (phone: 610-832-9728; E-mail: [email protected]).

‘Design Squad’ TV show coming on PBS

“Design Squad,” a PBS live-action series, will debut this year. Produced as an educational initiative, its goal is to excite kids about engineering while making it engaging and fun at the same time.

“Design Squad” is a new reality com-petition show consisting of two teams of high-school students (ages 16-19) who use their everyday problem-solving skills to design, construct, and test whimsical machines and innovative products for actual clients. In each episode, teens undertake real-world engineering chal-lenges—from designing a “summer sled” for L.L. Bean to making an automatic soccer ball machine for the MLS pro soc-cer New England Revolution team—and score points for their abilities at creative thinking and meeting project demands. These challenges ultimately lead to the top two scorers battling for the grand prize, a $10,000 scholarship from the Intel Foundation.

In addition to the television series, “Design Squad” is collaborating with engineering organizations and infor-mal educators to increase students’ knowledge and foster a positive image of engineering, often called the stealth profession because most people do not fully understand it. Through after-school

programs, museums, and outreach events nationwide, “Design Squad” will present engineering concepts and hands-on ac-tivities in an accessible and fun way.

The series premiere on PBS, and re-lated events, will kick off during National Engineers Week, Feb. 18-24, 2007.

For more information, visit the preview Web site at: pbskids.org/designsquad.

Correction

The number of “geosynthetics pio-neers” recognized at 8-ICG in Yokohama, Japan, last fall was printed incorrectly in the October/November 2006 issue.

The corrected complete sentence should read: The opening ceremonies of the 8th International Conference on Geo-synthetics on Sept. 19, 2006, featured a speech by Dr. J. P. Giroud on the history of the IGS, followed by the introduction of 16 pioneers who were in attendance at 8-ICG in Yokohama.

An unanswered question can stop your business in its tracks.

The GMA Techline will put you back in the fast lane.

The Geosynthetic Materials Association (GMA) is pleased to provide the GMA Techline, a resource for technical questions about geosynthetics.

Don’t second guess, get expert advice.

E-mail [email protected] for fast, free and direct answers to your technical questions.

GMA serves as the central resource for information regarding geosynthetics and provides a forum for consistent and accurate information to increase the acceptance and to promote the correct use of geosynthetics. Visit www.gmanow.com for more information.

[email protected]


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12-16 FebruaryIECA Environmental Connection, Reno

Environmental Connection ‘07, IECA’s annual conference and expo (the expo is Feb. 13-15), is your connection to the ero-sion and sediment control industry.

Quality education combined with a world-class expo makes this event a must for: contractors, developers, engineers, consultants, regulators, inspectors, gov-ernment agencies, landscape architects, manufacturers, educators, and students.

Twenty full-day training courses are offered, addressing topics such as wind erosion, construction-site management, and NPDES regulations and compliance. PHDs and CEUs are available.

More than 50 case studies and technical papers will be presented, providing origi-nal research and proven techniques to help you stay ahead in a competitive market.

More than 160 vendors will show par-ticipants the latest products and technology available in the largest expo dedicated to erosion and sediment control. The expo floor is a great place to see the latest in prod-ucts, services, and technologies.

The EC’07 event expects more than 2,300 attendees to network with for in-creased exposure, business opportunities, and resources.

Note: Environmental Connection 2007 is the only time you can earn your “IECA Trained” credits at one event.

EC’07 expo: Feb. 13–15, 2007, Reno-Sparks Convention Center, Reno, Nev.

For more information: International Erosion Control Association, 3001 S. Lincoln Ave. Suite A, Steamboat Springs, CO, 80487 USA; phone: 970-879-3010; fax: 970-879-8563; E-mail: [email protected]; www.ieca.org.

18-21 February Geo-Congress/2007, Denver

Geo-Denver 2007 at The Adam’s Mark in Denver, Colo., will provide pro-fessionals and students in all specialty fields with information about innovative and emerging technologies needed to advance geotechnical engineering and related disciplines. The congress will involve consulting engineers, general contractors, sub-contractors, owners, as well as educators, researchers and students. The planned congress sched-ule includes short courses, workshops,

plenary lectures, mini-symposia, panel discussions, and technical sessions in all fields of geotechnical engineering and related geo-professions.

Also planned are extensive exhibits, diverse field demonstrations and pre- and/or post-congress events, including field trips. The scope of the congress is broad based with direct participation from all 26 Geo-Institute Technical Com-mittees in the development of the pro-gram and technical activities.

For more information: www.geocon-gress.org; The Geo-Institute of the ASCE, 1801 Alexander Bell Dr., Reston, VA 20191-4400; 800-548-2723 (voice), 703-295-6350 (voice), 703-295-6351 (fax).

22-23 FebruaryHighway Bridge Design and Strengthening Using LRFD, Las Vegas

The purpose of this seminar is to con-centrate on the fundamentals of LRFD (Load and Resistance Factor Design) for highway bridge design and strengthening.

The LRFD approach is broken down into its basic components and a detailed explanation is provided on how and why each component was developed. The course will provide a practical intro-duction to the many new technologies advanced in the LRFD Specifications, including the limits states design phi-losophy, the use of notional live load models, and the application of structural reliability methods to achieve a more uniform level of safety in bridges.

LRFD live load models, load factors, distribution factors, load combinations, and design provisions for steel and con-crete bridges will be reviewed and il-lustrated, with detailed design examples with step-by-step explanations.

For more information, including costs, U.S. and Canada toll-free: 800 488 4775.

5-6 March Improving Public Works Construction Inspection Skills, Course #H639Allentown, Pa.

This course will be conducted March 5-6 in Allentown.

Among the topics covered: contracts and specifications, soils fundamentals, water and sewer construction, concrete and asphalt pavement construction, geosynthetics ap-plications, and erosion-control techniques.

The course instructors are professional engineers dedicated to providing an interac-tive learning experience, aiding participants in solving problems, and understanding situations applicable for the participants.

Participants can earn Continuing Edu-cation Units (CEU), and Professional Development Hours (PDH).

The fee covers course notebook and other materials, break refreshments, lunches, and certificate.

Course fee: $695. For more informa-tion or to register: 608 262 1299; 800 462 0876; epd.engr.wisc.edu.

7-8 MarchMaintaining Asphalt Pavements, Course #H625Allentown, Pa.

This course will be conducted March 7-8 in Allentown.

Among the topics covered: asphalt pavement performance; pavement evalu-ation, construction, and treatment; crack sealing, patching, and parking lots.

Participants can earn Continuing Edu-cation Units (CEU), and Professional Development Hours (PDH).

The fee covers course notebook and other materials, break refreshments, lunches, and certificate.

Course fee: $695. For more informa-tion or to register: 608 262 1299, 800 462 0876; epd.engr.wisc.edu.

13-14 March 9-10 OctoberExploring Plastics Extrusion course; Multilayer Structures course: Rapra one-day and a half-day coursesShawbury, England

Course overview: Products containing multiple layers of polymers are becom-ing more common, especially in applica-tions where barrier properties, strength, weight, or cost are an issue. This course will look at the wide range of properties that can be obtained, the production pro-cesses to achieve them and the practical extrusion technologies used.

Who will benefit? Technical manag-ers, marketing personnel, production managers, and process engineers work-ing within the polymer processing indus-try; technical sales personnel working for materials or machinery suppliers; quality, technical service, or purchasing

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http://www.ieca.org


http://www.geocon-gress.org



STAND OUTfrom the competition

IECA connects youwith other professionals

• Government

• Designers/Specifiers

• Contractors/Builders

IECA boosts your credibilitywith your peers and your customers

Learn how IECA can help you stand out at www.ieca.org/StandOut

from the competition

• Webinars

• IECA Publications

• In-House Training

• Online Resources

IECA provides the targeted training you needfor todays critical soil and water issues

Get “IECA Trained”Visit our websitefor more information

Join Today! www.ieca.org

800.455.4322 • 970.879.3010

STAND OUT

• EC07 February 12-16, 2007Reno, Nevada USA

• EC08 February 18-21, 2008Orlando, Florida USA

ANNUAL CONFERENCE & EXPO

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personnel in industries that use multi-layer structures in their products; de-signers and others involved in product development who want to gain a greater understanding of the properties derived from the processing methods for achiev-ing multilayer structures.

Course content: processing technolo-gies, polymer selection, product design, properties of various barrier polymers, forming multilayer polymer melts, line layouts, quality and process control, possible faults and troubleshooting.

Objectives: Understanding the ben-efits and cost implications with multi-layer structures, understanding the poly-mer properties needed to provide barrier resistance, making informed choices when purchasing equipment, identify-ing the equipment required to produce multilayer structures, and recognizing the faults in multilayer products from extrusion processes.

Tutors: Dr. Peter Cox, B.Sc. (Eng), DIC., C.Eng., MI Mech.E., FIM—Peter Cox Associates; and John Colbert, I. Mech. E.—John Colbert Extrusions

Fees: £495 ($630 U.S.) plus VAT, with discounts available for companies registering 2 delegates (10%) or 3 or more delegates (15%); 10% discount for anyone registering for both the “Ex-ploring Plastics Extrusion” training course as well as the “Multilayer Struc-tures” course.

For more information: www.rapra.net. To register: contact the Training Depart-ment at: [email protected]; +44 (0) 1939 250383.

26-29 MarchGEMMS 2007: “Zero Downtime” The Grand Hyatt, Singapore

The Global Executive Mining Main-tenance Summit (GEMMS) 2007 is a four-day conference and workshop tai-lored for maintenance practitioners in the mining industry. The event includes: professional training from world recog-nized experts, case-study learning ex-periences, and one-on-one maintenance plan consultations.

The 2007 event features the strategies and latest techniques used by the world’s most successful mining companies, aca-demics and consultants regarding their approaches to achieving maximum cost-

savings and productivity. It also includes a Strategic Maintenance Forum led by four international mine maintenance con-sultants who will help you streamline your own maintenance plan.

This year, GEMMS is held in con-junction with the Asia Mining Congress, which is attended by more than 300 min-ing CEOs, CIOs and COOs, Asia’s regu-lators and leading industry players.

For more information and to register, please call customer service: +65 6322 2700; E-mail: [email protected]; www.terrapinn.com

Host contact information: Terrapinn Pte. Ltd.Lynn Chew1 Harbourfront Place#18-01 Harbourfront Tower 1Singapore 098633Phone: (65) 6322 2729Fax: (65) 6271 8057E-mail: [email protected]

29 April—2 MayFifth Annual International Greening Rooftops for Sustainable Communities Conference, Awards, and Trade Show, Minneapolis

Cohosted with the city of Minneapo-lis, this conference is organized by Green Roofs for Healthy Cities (GRHC) a not-for-profit industry association working to promote the green roof industry in North America.

The 2007 conference will consist of plenary and specialized sessions focused on three main topic areas:

1. Policies and Programs to Support Green Roofs

2. Green Roof Design and Implemen-tation

3. Research and Technical Papers on Green Roof Performance

The 2007 full registration package includes:

• Access to more than 50 presentations by green roof industry leaders

• Free pass to the trade show featur-ing more than 75 exhibitors showcasing green roof products and services

• Access to the Exhibitor Presentation Theatre and Poster Sessions

• One copy of the official conference proceedings CD-ROM featuring the peer-reviewed speaker papers (retail value $75)

• One invitation to the Awards of Ex-cellence Luncheon (May 1)

Online registration will be available through this site: greenroofs.org.

All delegates at the 2007 conference will receive a complimentary, one-year individual membership in Green Roofs for Healthy Cities, effective June 1, 2007. This membership entitles dele-gates to a host of benefits, including a two-line description on the searchable online membership database, member-ship listing in the Members Directory Conference CD-ROM, a $25 discount on CD-ROM conference proceedings from the 2003 Chicago, 2004 Portland, 2005 Washington, and 2006 Boston confer-ences, and a hardcopy subscription to the semiannual Green Roof Infrastruc-ture Monitor™ publication highlighting the latest technical, policy, and prod-uct developments in green roof infra-structure, presented by Green Roofs for Healthy Cities

Conference and trade show location: Hyatt Regency Minneapolis Hotel.

Trade show: The trade show is open free of charge to all delegates, including those individuals with one-day passes. Trade-show only passes will also be avail-able for purchase independently.

For more information: www.greenroofs.org.

12-13 JuneNanopolymers 2007,First International Conference Berlin, Germany

Rapra Technology will conduct the first international Nanopolymers Confer-ence in Berlin June 12-13, 2007. Nano-technology is already making a major impact on new product introductions throughout the world via many industry sectors. These new products are based on the material property changes that may be achieved by incorporation of ingredients, at the nanoscale, into poly-meric systems.

Although nanoparticulate carbon black has been used in vehicle tires for decades, it is only recently that other nanoparticulate ingredients have been dispersed in plastics to provide new materials that are lighter weight and as strong as metals. The textiles industry and the sporting goods industry are also

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http://www.terrapinn.com

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50% off price!Introductory offer – Subscribe today and SAVE!

They don't call us Geosynthetics for nothing.We're the complete industry expert offering topics on:

Roads & bridges

Erosion control

Landscape architecture

Water management

Retaining walls

and much, much more!

•

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Name ____________________________________ Company ________________________________________

Address ____________________________________________________________________________________

City _____________________________________ State ______________________ Zip ___________________

Phone ____________________________________ Fax _____________________________________________

❏ Bill me❏ Check Enclosed $ ___________________❏ Credit Card Payment ❍ Visa ❍ Master Card ❍ Amex ❍ Discover

Card Number ___________________________________________

Expire Date _____________________________________________

Card Holder Name _______________________________________

Signature ____________________________ Date _______________

Title (please check):❑ Owner/Corporate executive

❑ Chief/Staff Engineer

❑ Geotechnical Engineer

❑ Civil Engineer

❑ Research/Development Professional

❑ Other (please specify)____________

Type of Business (please check):❑ Engineering Firm /Engineer in Private Practice

❑ Contractor

❑ Geosynthetic Installer

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❑ Other (please specify)_______________

❑ $61 $30 /Year U.S.A.

❑ $74 $37 /Year Canada/Mexico (U.S. funds)

❑ $102 $51 /Year Other Int'l (U.S. funds)

Fax: +1 651-631-9334Mail: IFAI, SDS-12-2108, PO Box 86, Minneapolis, MN 55486-2108

Offer ends March 31, 2007. Please allow 4-6 weeks for shipment of fi rst issue. Offer valid for new subscribers only.

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introducing nanotechnology based prod-ucts, and it is estimated that there are now more than 700 nano-based products on the market.

The main “nano” ingredients being dispersed in polymeric systems are es-pecially organoclays, nanoparticulate inorganics, and carbon nanotubes.

Register before April 12 to take ad-vantage of the special Early Bird Dis-count registration fee:

Companies sending one or two del-egates—€850 per delegate before April 12; €1050 per delegate after April 12.

Companies sending three or more del-egates—€750 per delegate before April 12; €950 per delegate after April 12.

For more information: www.berlin-tourist-information.de/index.en.php

Contact the conference department by telephone: +44(0)1939-250383; or E-mail: [email protected]

Please send reservation inquiries to: Sharon Garrington via E-mail: [email protected]

20-22 June51st Annual Construction Specifications Institute (CSI) Show and ConventionBaltimore Convention CenterBaltimore, Md.

CSI’s staff, task teams and committees have reviewed hundreds of education proposals in an effort to find the best technical and professional development presentations for The CSI Show 2007.

The good news is that the pool of po-tential candidates was outstanding this year. Among the sessions and tracks of-fered in June: Specifications & Design; Sustainability; Professional Development & Leadership; Contract Documents; and Building Information Modeling.

CSI is also revamping some of the exhibit hall features, including addition of a Product Education area, free E-mail stations, and membership and certifica-tion features in the CSI booth.

Convention and lodging registration will open March 2007.

Host contact information:

Construction Specifications Institute (CSI)99 Canal Center Plaza, Suite 300Alexandria, VA 22314Phone: 703 684 0300; 800 689 2900Fax: 703 684 8436E-mail: [email protected]

25-29 JuneU.S. Army Corps of Engineers Infrastructure Systems ConferenceMarriott Renaissance Center, Detroit

“The Future of Engineering in a Com-plex World” is the subtitle for this USACE event in Detroit in June.

The conference will address the Corps’ 12 Actions for Change—a set of directions that the Corps will focus on to transform its priorities, processes, and planning. These actions fall within the themes: com-prehensive systems approach, effective and transparent communication, and reli-able public service professionalism.

To register or for more information, go to: www.usaceiscconf.org.

Geosynthetic Materials AssociationOur Mission:The Geosynthetic Materials Association serves as the central resource for information regarding geosynthetics and provides a forum for the correct use of geosynthetics.

Objectives:GMA actively identifies, assesses, analyzes, and acts upon market growth opportunities and issues that affect its member companies. The activities of the association are proactive in nature and center on five areas:• Engineering support • Business development • Education • Government relations • Geosynthetics industry recognition

To l e a r n m o r e a b o u t G M A v i s i tw w w. g m a n o w. c o m


For more information: Geosynthetic Materials AssociationPhone: +1 651 225 6907 or 800 636 5042

E-mail: [email protected] • Web site: www.gmanow.com

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| Advertisers Index |

| When you contact an advertiser in this issue, please tell them that you saw their ad in Geosynthetics. For advertising rates and

information call Sarah Hyland at 800 319 3349

Agru America800 373 AGRUwww.agruamerica.com . . . . . . . . . Cv2GMA Member

American Wick Drain Corporation800 242 WICKwww.americanwick.com. . . . . . . . . . 32GMA MemberAtarfil S.L.+34 958 43 92 00www.atarfil.com . . . . . . . . . . . . . . . . 33GMA Member

Brockton Equipment/Spilldam Inc.800 699 2374www.spilldam.com . . . . . . . . . . . . . . 46

Burke Environmental Products800 669 7010www.burkeind.com . . . . . . . . . . . . . 23

Carlisle SynTec Inc.800 4 SYNTECwww.carlislegeomembranes.com . . 17

CETCO+1 847 392 5800www.cetco.com/lt . . . . . . . . . . . . . . . 38GMA Member

DEMTECH Services Inc888 324 WELDwww.demtech.com . . . . . . . . . . . . . . . 7

Engepol Ltda+55 11 4166 3060www.engepol.com . . . . . . . . . . . . . . 13 Fiberweb800 284 2780www.typargeotextiles.com . . . . . . . . 9GMA Member

Firestone Specialty Products Co.800 428 4442www.firestonesp.com . . . . . . . . . . . 10GMA Member

| The Geosynthetic Materials Association is directed by the needs of the North American geosynthetics industry. It serves as the central resource for information regarding geosynthetics and provides a forum for consistent and accurate information to increase the acceptance and to promote the correct use of geosynthetics. Visit www.gmanow.com, Contact: Andrew Aho [email protected], 800 636 5042.

Huesker Inc.800 942 9418www.hueskerinc.com . . . . . . . . . . . . 43GMA Member

Contech Earth Stabilization Solution, Inc.800 338 1122www.contechess.com . . . . . . . . . . . . 29

Layfield Geosynthetics & Industrial Fabrics Ltd.888 225 4436www.geosyntheticbarriers.com . . . . 19GMA Member

Leister Process Technologies800 241 4628www.leister.com . . . . . . . . . . . . . . . . 45 LG Chem America Inc.+1 201 266 2533www.lgchem.com . . . . . . . . . . . . . . . . 3

Lock & Load877 901 9998www.lock-load.com . . . . . . . . . . . . . 25

Maccaferri Inc.800 638 7744www.maccaferri-usa.com . . . . . . . . . 31GMA Member

Naue GmbH & Co. KG+49 5743 41-0www.naue.com . . . . . . . . . . . . . . . . . 24

Permathene Ltd.+64 (0)9 968 8888www.permathene.com . . . . . . . . . . . . 5

Plastic Welding Technologies800 635 6693www.pwtworld.com . . . . . . . . . . . . . 36

Propex888 319 7773www.geotextile.com/strongerroads . 1GMA Member

Raven Industries Inc800 635 3456www.rufco.com . . . . . . . . . . . . . . . . 39GMA Member

SKAPS Industries706 354 3700www.skaps.com . . . . . . . . . . . . . . . . 33GMA Member

Solmax International, Inc.800 571 3904www.solmax.com . . . . . . . . . . . . . . . 37GMA Member

SRW Products800 752 9326www.srwproducts.com . . . . . . . . . . 45

Strata Systems Inc.800 680 7750www.geogrid.com . . . . . . . . . . . . . Cv3GMA Member

Tenax Corp.800 356 8495www.tenaxus.com . . . . . . . . . . . . . Cv4GMA Member

TenCate Geosynthetics800 685 9990www.mirafi.com . . . . . . . . . . . . . . . . 11GMA Member

TRI/Environmental, Inc.+1 512 263 2101www.GeosyntheticTesting.com . . . . 18GMA Member

Trelleborg Building Systems AB+1 46 370 481 00www.trelleborg.com/rubber_membranes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Watersaver Co. Inc.800 525 2424www.watersaver.com . . . . . . . . . . . . . 5

GEOAMERICAS 2008The First Pan American Geosynthetics Conference & Exhibition.March 2-5 2008Hilton Cancún Beach & Golf Resort, Boulevard Kukulcan Km 17, Zona HoteleraCancún, Quintana Roo, Mexico 77500 For more information go to www.geoamericas.info

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http://www.GeosyntheticTesting.com

http://www.trelleborg.com/rubber_membranes

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http://www.agruamerica.com

http://www.americanwick.com

http://www.atarfil.com

http://www.spilldam.com

http://www.burkeind.com

http://www.carlislegeomembranes.com

http://www.cetco.com/lt

http://www.demtech.com

http://www.engepol.com

http://www.typargeotextiles.com

http://www.firestonesp.com

http://www.hueskerinc.com

http://www.contechess.com

http://www.geosyntheticbarriers.com

http://www.leister.com

http://www.lgchem.com

http://www.lock-load.com

http://www.maccaferri-usa.com

http://www.naue.com

http://www.permathene.com

http://www.pwtworld.com

http://www.geotextile.com/strongerroads



| Final Inspection |

| Contact the Geosynthetic Materials Association (GMA) at: +1 651 225 6907; 800 636 5042;

Fax +1 651 631 9334; Web site www.gmanow.com

GMA members see, hear about Army Corps’ progress in New OrleansBy Andrew Aho

Last October, I accompanied a GMA delegation that traveled to New Orleans to meet with mem-bers of the New Orleans District office of the U.S. Army Corps of Engineers. Our discussion included about a dozen engineers at their just-reopened facility in the city.

I was struck by the sense of urgency and the sense of purpose that was palatable in the build-ing. Everyone seemed stressed but mission-focused. The critical

mission: rebuild the levees and protection system for New Orleans and the surrounding area. All the projects were on a fast track, of course, in an effort to provide defenses against the next storm.

During our meeting, John Bivona, chief of this district’s geotechnical branch, reviewed levee projects that incorporated geotextiles and geogrids. He said the Army Corps had much praise for geosynthetic materials used in this construction.

Further, he said that by incorporating geosynthetics the Army Corps was able to make the levees higher and stronger without expanding the footprint or base that is often immedi-ately adjacent to streets or buildings. Bivona also said geosyn-thetic materials helped stabilize the poor soils encountered in the rebuilding projects and said they are used as a substitute for good fill that is hard to find in the New Orleans area.

The Army Corps provided GMA with a map and a list of the more than 160 rebuilding and reinforcement projects that they were overseeing. They also provided GMA with a list of consulting firms that are working with the Corps. The engi-neers urged members of the GMA delegation to contact the design and consulting firms working in New Orleans to educate them about the advantages of using geosynthetic products in their projects.

The Army Corps has made tremendous progress repairing and protecting New Orleans. The task before them seems daunting. And although many of the employees suffered personal losses themselves, they are not intimidated. Their professionalism and dedication should be recognized and appreciated by all of us.

| Andrew Aho, Managing Director, Geosynthetic Materials Association


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Photos courtesy of Brent Christenson

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