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 June 2007
Tech News

Geosynthetics Subcommittees Developing a Variety of Proposed New Standards

Three subcommittees of ASTM International Committee D35 on Geosynthetics are currently developing several proposed new standards. The topics covered in the following proposed standards are geosynthetic clay liners, geomembranes, and the development of a mechanistic-empirical design guide for pavements.

ASTM meeting and staff manager contact information for Committee D35 can be found at the end of this article.

Subcommittee D35.04 on Geosynthetic Clay Liners

Responding to shrinkage issues involving geosynthetic clay liners (GCLs), Subcommittee D35.04 has launched work on a proposed new standard, WK12239, Test Method for Linear Dimensional Changes of Restrained Geosynthetic Clay Liners Under Cyclic Temperature and Hydration Conditions.

Studies have shown that GCLs, when covered with a geomembrane and left exposed (for example, with no cover soil), can shrink in the width-wide direction. According to Richard Erickson, D35.04 member and senior engineer, Vector Engineering, Inc., the shrinkage is due primarily to cyclical wet-dry cycling of the GCL under the geomembrane and in contact with a soil subgrade.

“This has become an alarming situation when designing and constructing with GCLs, and their long-term performance as hydraulic barriers,” says Erickson. “Currently there are two technical papers and a GRI white paper that was developed by the Geosynthetic Institute that discuss the phenomenon and concern regarding GCL panel separation. Development of a related ASTM standard is a proactive step within Subcommittee D35.04 to develop a methodology that evaluates GCL shrinkage.”

WK12239 is an index test that covers the measurement of changes in linear dimensions of a geosynthetic clay liner that result from exposure to changes in temperature and moisture conditions over time.

“The proposed standard will be used to evaluate product-specific and project-specific potential shrinkage for GCLs exposed to changes in moisture and temperature conditions,” says Erickson. “Measured shrinkage can then be utilized by designers and construction quality assurance monitors in compensating specified GCL overlaps to allow for anticipated GCL panel shrinkage.”

While participation in the development of WK12239 has been primarily limited to GCL manufacturers and independent test laboratories, Erickson says Subcommittee D35.04 would like to expand the circle of participants. All interested parties, particularly those from the design and construction quality control/assurance areas are invited to join in the ongoing development of WK12239.

CONTACT

Technical Information: Richard Erickson, Vector Engineering, Inc., Grass Valley, Calif.
Phone: 530/272-2448

Subcommittee D35.10 on Geomembranes

Subcommittee D35.10 is currently developing two proposed new standards, WK14305, Specification for Non-Reinforced PVC (Polyvinyl Chloride) Geomembrane Seams, and WK14311, Guide for the Installation of Non-Reinforced Polyvinyl Chloride (PVC) Geomembranes.

According to Mark Wolschon, Environmental Protection, Inc., Mancelona, Mich., engineers, specification writers, users, suppliers, manufacturers, fabricators and installers of PVC geomembranes will be able to work with WK14305, hand-in-hand with D 7176, Specification for Non-Reinforced Polyvinyl Chloride (PVC) Geomembranes Used in Buried Applications, in the design and construction of commercial, municipal and residential projects. “Typical projects using PVC geomembrane are landfills, wastewater lagoons, retention ponds and decorative ponds,” says Wolschon.

A lack of industry consensus on how geomembrane installations should be done in the field is the impetus behind WK14311. This proposed guide would be used in conjunction with other specifications to offer engineers and contractors a reference regarding the typical conditions and minimum standard they should expect from their PVC geomembrane supplier and installer.

“We would like to see more participation by the rest of the PVC geomembrane industry,” says Wolschon. “We will also need to conduct round robin testing of many of the recent specifications, including D 7176 and D 7177, Specification for Air Channel Evaluation of Polyvinyl Chloride (PVC) Dual Track Seamed Geomembranes.”

“EPI has made a long-term commitment to remain involved with ASTM and recruit our manufacturers, suppliers and our competition to ASTM,” says Wolschon. “Our belief is that once an ASTM standard, guide or specification has been approved, it is widely accepted by the industry and proven to be a useful tool for everyone involved.”

CONTACT

Technical Information: Mark Wolschon, Environmental Protection Inc.,
Mancelona, Mich.
Phone: 800/655-4637

Subcommittee D35.01 on Mechanical Properties

There is currently a national movement to develop a mechanistic-empirical design guide for pavements. This initiative requires that the fundamental material properties for all components of the design be quantified. Subcommittee D35.01 is working toward this goal with the development of two proposed new standards, WK14361, Test Method for Determining Small-Strain Tensile Properties of Geogrids and Geotextiles by In-Air Cyclic Tension Tests, and WK14362, Test Method for Measuring Geosynthetic-Soil Interface Shear Modulus.

“When geosynthetics are used to reinforce the base course layers of flexible pavements, two main design parameters required are the interaction between the geosynthetic and the surrounding aggregates, and the tensile properties of the geosynthetic,” says Eli Cuelho, research engineer with the Western Transportation Institute and a member of D35.01.

Cuelho notes that, while these properties are traditionally determined using static or semi-static loading, the most relevant interaction tests use cyclic loads like those experienced in transportation applications. However, there are currently no tests to quantify soil/geosynthetic interaction properties or tensile properties of the geosynthetic when subjected to cyclic loading. WK14361 and WK14362 will provide standards for these tests.

“These proposed standards will eventually be used to determine geosynthetic material properties that will be directly utilized in the design of geosynthetic-reinforced pavements when the geosynthetics are used as reinforcement of the base layer,” says Cuelho. The most likely users of the proposed standards are commercial testing laboratories that will run the tests for manufacturers and designers.

All interested parties are invited to join in the standards developing activities of Subcommittee D35.01. //

CONTACT

Technical Information: Eli Cuelho, Western Transportation Institute, Montana State University, Bozeman, Mont.
Phone: 406/994-7886

ASTM Staff: Christine Sierk
Phone: 610/832-9728

Upcoming Meeting:
June 27-29
June Committee Week
Norfolk, Va.