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The Sanitary Landfill 333
10.4.24 GEOSYNTHETIC MATERIALS
Geosynthetic materials comprise a wide group of polymer-based mats, sheets, grids, nets, and com-
posite materials that have found extensive use not only in modern landfills but in water management
and other engineering applications. Depending on design, geosynthetics perform five major func-
tions: separation, reinforcement, filtration, drainage, and containment (Koerner, 1998). Several
common geosynthetics will be discussed below.
Geonets (also known as geospacers) are used to convey liquids (Figure 10.23a). Geonets are
plastics formed into a rather tight, grid-like configuration. A geonet can be defined as (ASTM, 2002):
a geosynthetic material consisting of integrally connected parallel sets of ribs overlying similar sets
at various angles for biaxial or triaxial drainage of liquids or gases. Geonets are often laminated with
geotextiles on one or both surfaces and are then referred to as drainage geocomposites.

Geonets are manufactured with layers of intersecting ribs designed so that liquid can flow
within the open spaces. Geonets vary in thickness from 4.0 to 6.9 mm (U.S. EPA, 1993). Geonets
require the installation of a geotextile above them.
Geotextiles (also known as filter fabrics) are defined as (ASTM, 2002):

A permeable geosynthetic comprised solely of textiles. Geotextiles are used with foundation, soil, rock,
earth, or any other geotechnical engineering-related material as in integral part of a human-made project,
structure, or system.

FIGURE 10.23 Common geosynthetic materials: (a) geonet; (b) geotextile; (c) geogrid; and (d) geosynthetic
clay liner.