NEW DELHI: A mixture of tyre crumb and sand, if placed beneath and around a building foundation, can help the structure resist an earthquake jolt, claims a study by the Indian Institute of Science (IISc).
A team conducted several experiments to come up with the right mixture of sand and tyre crumb, and found that a combination of 75 per cent tyre crumb and 25 per cent sand to be the best composition.
A tyre crumb is a granular material recovered from recycled waste tyres.
"When rubber tyres are filled with small stones (rock aggregates), they can absorb up to 70 per cent of the earthquake's forces.
"Our studies show that the sand-rubber mixtures can reduce the earthquake impact by 40-50 per cent in comparison with conventional soil fill for low to moderate rise structure," said Anbazhagan, an assistant professor at Department of Civil Engineering at IISc, said.
The study found that the mixture of sand and tyre crumb served as cushions, absorbing the sliding forces parallel to the ground. Imparting flexibility to the structure due to cushioning action of tyre crumb sand layer, not only reduces the seismic load, but also reduces the permanent displacement of the structure, the study claimed.
Civil engineers at IISc said this new technology, when developed, will have two important benefits: build earthquake resistant buildings that can potentially save lives during a disaster and develop a sure shot way to reuse millions of used tyres.
Geologically, India is a huge plate that is going northward at a pace of about 50 millimetre every year. Indian plate boundaries are capable of producing moderate to mega earthquakes. No wonder, by area, more than half of India is vulnerable to earthquakes making the lives of about 200 million city-dwellers more risky.
Earthquake resistance aside, could this new technique possibly pollute the soil and ground water? "Not likely", Anbazhagan said. "Evidence shows that rubber present above ground water table does not contaminate the water table. In this study, we propose a geotechnical isolation system using rubber-sand mixtures. This rests above the ground water table," he added.