HYDERABAD: Can an ancient civil engineering technique be used in the modern era for developing earthquake-resistant buildings?
A team of civil engineering researchers from Hyderabad are studying the Kakatiya dynasty-era ‘sandbox’ technique of laying foundation to make a building earthquake-resistant.
The ‘sandbox’ technique was quite unique to Kakatiya dynasty and was used by Kakatiya rulers for construction of the famous Ramappa Temple and the Thousand Pillar Temple in Warangal. And the two temples, which are unaffected by seismic disturbances for hundreds of years, now stand testimony to the effectiveness of that technique.
The technique
The technique involved filling the pit — dug up for laying foundation — with a mixture of sand-lime, jaggery (for binding) and karakkaya (black myrobalan fruit) before the buildings were built on these ‘sandboxes’.
Dr Venkata Dilip Kumar Pasupuleti, Assistant Professor, School of Engineering Sciences at Mahindra Ecole Centrale in Hyderabad, who is leading the study on the ‘sandbox technique’ for the last one-and-a-half years, said, “The sandbox in the foundation acts as a cushion in case of earthquakes. Most of the vibrations caused by earthquake lose their strength while passing through the sand by the time they reach the actual foundation of the building.”
“Although techniques similar to sandbox have been found to be employed in other parts of the world, but usage of sand is probably unique to Kakatiya dynasty as in other places mud or stones were used,” he added.
Sandbox technique is not being used anymore, but Dr Pasupuleti feels confident that it can be used even now, for making concrete buildings earthquake-resistant and that sandbox technique is even long-lasting and more beneficial than the modern techniques. He said that presently, Elastomeric Base Isolation technique is used in making a building earthquake-resistant, as part of which rubber is used in the foundation. But this gets worn out in a span of 30-40 years.
Limitations
In sandbox technique, sand is used, whose weathering is very slow, as a result of which it can last for hundreds of years. However, the technique cannot be used in construction of tall buildings like skyscrapers though it can be easily used in shear-predominant structures, which are the most common form of buildings in India.