ETL 1110-1-189
14 Feb 03
USE OF GEOGRIDS IN
PAVEMENT CONSTRUCTION
1.0 Introduction
Engineers are continually faced with maintaining and developing pavement infrastructure
with limited financial resources. Traditional pavement design and construction practices require
high-quality materials for fulfillment of construction standards. In many areas of the world,
quality materials are unavailable or in short supply. Due to these constraints, engineers are often
forced to seek alternative designs using substandard materials, commercial construction aids, and
innovative design practices. One category of commercial construction aids is geosynthetics.
Geosynthetics include a large variety of products composed of polymers and are designed to
enhance geotechnical and transportation projects. Geosynthetics perform at least one of five
functions: separation, reinforcement, filtration, drainage, and containment. One category of
geosynthetics in particular, geogrids, has gained increasing acceptance in road construction.
Extensive research programs have been conducted by the U.S. Army Engineer Research and
Development Center (ERDC) and non-military agencies to develop design and construction
guidance for the inclusion of geogrids in pavement systems. This document describes the use of
geogrids in flexible pavement systems including design charts, product specifications, and
construction guidance.
A geogrid is defined as a geosynthetic material consisting of connected parallel sets of tensile
ribs with apertures of sufficient size to allow strike-through of surrounding soil, stone, or other
geotechnical material (Koerner 1998). Existing commercial geogrid products include extruded
geogrids, woven geogrids, welded geogrids, and geogrid composites. Extruded geogrids are
formed using a polymer sheet that is punched and drawn in either one or two directions for
improvement of engineering properties. Woven geogrids are manufactured by weaving polymer
fibers, typically polypropylene or polyester, that can be coated for increased abrasion resistance
(Berg et al. 2000). Welded geogrids are manufactured by welding the junctions of woven
segments of extruded polymers. Geogrid composites are formed when geogrids are combined
with other products to form a composite system capable of addressing a particular application.
Extruded geogrids have shown good performance when compared to other types for pavement
reinforcement applications (Cancelli et al. 1996, Miura et al. 1990, and Webster 1993). Extruded
geogrids can be divided into two broad categories based upon their formation and principle
application, uniaxial and biaxial. Extruded geogrids that are pre-tensioned in one direction are
called uniaxial geogrids and are typically used in geotechnical engineering projects concerning
reinforced earth and retaining walls. Extruded geogrids that are pre-tensioned in two directions
are referred to as biaxial geogrids and are typically used in pavement applications where the
direction of principle stress is uncertain. Most geogrids are made from polymers, but some
products have been manufactured from natural fibers, glass, and metal strips. This document,
however, will focus exclusively on polymer-based geogrids.
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