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September 20, 2002

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Stopping Landslides in Rio: Recycling Scrap Tires into Retaining Walls

Keane Shore

April 30, 1999   

[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


Links to explore ...

Spanish version of this article

Sidebar: Tire Walls: A Partnership of Engineers and Social Scientists

Building One's House of Adobe, by André Lachance

Natural Disaster Prevention (Costa Rica)

Quake-proof Adobe Housing (Peru)

Volcanoes and Earthquakes — Disaster Prevention

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