Geosynthetics June/July 2019 - 15

CASE STUDIES

Geogrid reinforced soil
structures reach new heights
By Sachin Mandavkar and Mehari Weldu

einforced soil structures are geotechnical systems consisting of reinforcing elements
and primarily include mechanically stabilized earth (MSE) walls and reinforced soil
slopes (RSS) (Figure 1). MSE walls and RSS are constructed by placing alternating layers
of reinforcement and compacted soil behind a facing element to form a composite material
that acts integrally to restrain lateral forces. In ancient times, a variety of materials were
used as soil-reinforcing elements, including tree branches and straw. Common types of
modern soil-reinforcing elements are steel strips, welded steel grids, wire mesh, geogrids
and geotextile sheets. The use of a facing system prevents soil raveling between the reinforcing elements and allows very steep slopes and vertical walls to be constructed safely.
A wide range of materials are used as facing, including precast concrete panels, dry cast
modular blocks, welded wire mesh, wraparound geosynthetics and gabions. The soil material placed within the reinforcement zone is referred to as reinforced fill, and the in situ
soil or backfill material placed directly behind the reinforced zone is termed as a retained
backfill. Figures 2 and 3 on page 16 show the main components of a generic MSE wall
and RSS system, respectively.
The use of MSE walls and RSS have progressively grown over the last four decades due
to advantages they provide compared to alternative soil-retaining structural systems. The
cost-effectiveness and simplicity of the construction technique, speed of construction and
flexibility of reinforced soil structures are among the benefits that make the technology
popular and very attractive. As described above, MSE walls and RSS can be reinforced
using metallic and geosynthetic-reinforcement materials. This paper, however, focuses
on geosynthetic-, particularly geogrid-, reinforced structures and does not address other
reinforcement types.
Geosynthetic materials have been developed and used as reinforcement in soil-retaining
structures since the early 1970s. The first geotextile-reinforced wall was constructed in
France in 1971, and the first structure of this type in the United States was constructed in
1974. Geogrids for soil reinforcement were developed around 1980. The first use of a geogrid
in soil reinforcement was in 1981, and extensive use of geogrid products in the United
States began in about 1983. Since the early 1980s, the use of geosynthetics in reinforced
soil structures has increased significantly, and they now comprise a growing portion of
the reinforced soil market. Technological developments in the polymer industry have

Sachin Mandavkar, P.E.,
M.ASCE, is technical director
at Maccaferri Inc.
Mehari Weldu, EIT, is associate
engineer at Maccaferri Inc.
All photographs and illustrations
courtesy of the authors.

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Geosynthetics June/July 2019

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