Water seepage, poor quality major causes for Bengaluru sinkholes: Experts

Inaccurate geometry of the road and failure to monitor road conditions can also result in sinkholes to appear, experts said

The three-meter-deep sinkhole that appeared on Brigade Road has yet again raised concerns over the quality of the roads in the city.

While potholes are a common sight in the city, many roads are now developing sinkholes.

Water seepage, failure to monitor the road conditions, inaccurate geometry of the road, and the poor quality of asphalt could be the major reasons why sinkholes develop, the experts opined.

“Bengaluru soil is high in silt content and this calls for better compaction. The reasons for such instances differ from location to location. In a few cases, the seepage of water might have left the soil loose. In a few others, excavation and dewatering nearby could have carried away the silt, creating a cavity,” explained Dr P Anbazhagan, from the Civil Engineering department of the Indian Institute of Science
(IISc).

Srikanth Channal, Chairperson of the Association of Consulting Civil Engineers, Bengaluru, opined that the Bruhat Bengaluru Mahanagara Palike (BBMP) needs to ensure that the asphalt is thick enough. “The asphalt should be at least three inches thick. However, the practice remains on paper, and on most of the roads, the asphalt is only one inch thick. When the quality is poor, it tends to peel off,” he said.

That apart, Channal also opined that the geometry of the road should be planned well. “There are cambers in the centre of the carriageways, which ensure the water flows off into the drains. However, when the cambers are not planned according to the height required for water flow, water tends to seep in, loosening the soil and making the asphalt brittle,” he said.

Anbazhagan opined that the use of preventive measures like strengthening the surrounding structures while dewatering and the use of ground-penetrating radars and other modern techniques to identify cavities deep inside could help prevent the formation of such sinkholes in the future.