[Photo: Tire wall under construction in Rio de Janeiro.]
Retaining walls made with recycled scrap tires are helping to raise
living standards in the favelas of Rio de Janeiro — areas that lack
basic sewage and sanitation services. Some two million people live in
these low-income communities, including more than one million people on
the hillsides above the city's core.
A team of
Canadian and Brazilian researchers has discovered that the tire walls —
built for less than one-third of the cost of conventional anchored
concrete retaining walls used elsewhere in the city — may be more
effective at stopping landslides during the rainy seasons. Rio de Janeiro
now spends about US$50 million per year on concrete retaining walls to
stop the slides, only to see some of them fail.
Landslides
Many landslides begin
when loose debris from illegal hillside garbage dumps becomes sodden and
topples under its own weight. The heavy material crashes into the mainly
plywood shack dwellings below, causing deaths and property damage every
rainy season.
The Rio project began when Vinod
Garga, an engineering professor at the University of Ottawa, and Luciano
Medeiros, then a visiting professor from Brazil, were planning a
low-cost retaining wall research project in Canada. They realized that the
hillside slum communities of Rio de Janeiro could benefit as well. In Rio
alone, more than three million tires are disposed of each year. Many of
these tires are illegally dumped or burned, threatening the quality of
both air and groundwater, and serving as a breeding ground for vermin,
insects, and disease.
Economically viable
"We thought this might be an economically viable
and environmentally sustainable way of building low-cost structures. These
walls could be constructed under engineering supervision, by the people
themselves," explains Dr Garga.
With financial
support from the International Development Research Centre, the project
team first built a test wall in an isolated area and embedded it with
measuring instruments to measure its performance. The team used a
specially designed saw to slice off one side wall in each tire, tied the
tires together in a honeycomb pattern using polypropylene rope, and packed
them full of compacted earth. The test walls were layered up to six metres
high. Most of this work involved staff and students in the departments of
Civil Engineering and Social Work at the Pontifícia Universidade Católica (PUC)
do Rio de Janeiro, with Dr Garga acting as project director. The team
was assisted by the Fundacao Instituto Geotecnica of the Municipality of
Rio de Janeiro (GEO-RIO), the agency responsible for building retaining
walls to assure slope stability.
Local
authorities
Even before the test wall was
finished, local authorities were so impressed that they constructed
another wall in one of the hillside slum communities. "After they
constructed the wall, GEO-RIO cleaned up gullies and provided drainage.
[Shortly after], they had torrential rainfalls — virtually chaotic
conditions," says Dr Garga.
It was a full-scale
test in an extreme event. The downpour caused several concrete walls to
collapse and several poor housing to be washed away elsewhere in Rio but
the tire structures held. Where there had initially been skepticism about
the wall — some people felt that as residents of a low-income area they
were being given a substandard replacement for concrete — there was now
total acceptance.
Sense of security
"This gave a great sense of security to the people:
this wall had passed, as it were, the test of fire. And a very interesting
social phenomenon occurred, which was a surprise to everybody," adds Dr
Garga. What happened was a small residential building boom.
"The quality of [home] construction just improved
tremendously because people now had security," he says. Moreover, "the
people started taking more pride in their community." In fact, local
citizens named a town square in the newly redeveloped area Praça
Projeto Pneus, or 'Tire Project Square'.
Wall building
The project team
hopes that favela residents will band together now to build their own
walls in other communities under engineering supervision. Indeed, after
seeing the wall's success on the hillsides, citizens' groups are already
adapting them for their own uses. One small fishing community on a swampy
tidal inlet in northern Rio collected tires to build a jetty, and planted
it with trees and shrubs to keep tidal water from washing into their
homes.
Dr Garga cautions that while the tire
wall is easily built by volunteers, and has stood some major tests, that
does not mean it cannot fail. "Engineering principles have to be observed
and applied to ensure a safe design. You can't disobey the laws of
physics, however forgiving the material might be."
Design limits
For his part, Dr
Garga would like to conduct more elaborate testing of the tire wall
structure, to determine its design limits. It is not yet known how high
the walls may be built, or how solid they will remain on very swampy or
compressible ground over the long term. He also hopes to prepare a tire
wall design manual for citizens' groups to use in Rio and around the
world.
Keane J. Shore is an Ottawa-based
writer and editor. (Photo: V. Garga)
[Reference: IDRC Project number 94-1005]
Resource Persons:
Dr Vinod Garga, Faculty of Engineering,
University of Ottawa, 161 Louis Pasteur St., (A-020), PO Box 450, Station
A, Ottawa, Ontario, K1N 6N5, Canada; Tel: (613) 562-5800, ext. 6143; Fax:
(613) 562-5173; E-mail: mailto:%20garga@genie.uottawa.ca
Dr Luciano
Medeiros, Pontifícia Universidade Católica do Rio de Janeiro, Rua
Marques de Sao Vicente 225, Gavea, Rio de Janeiro, CEP 22453 Brazil;
E-mail: mailto:%20luciano@civ.puc-rio.br
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Spanish
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