BENGALURU: A part of Kempegowda Road over the Metro tunnel caved in, creating a 2 ft wide and 10 ft deep hole, scaring the commuters on a busy Tuesday morning and exposing the shoddy work done by the Bengaluru Metro Rail Corporation Ltd (BMRCL) and other civic agencies.

Though the BMRCL claimed that it had taken all precautions while digging the tunnel, and that the exact reason behind the collapse was not known, experts said it was because of the vibrations caused by the tunnel boring machines and commercial operations of Metro trains. The recent heavy rains may have also contributed to the collapse, they said.

Mr Sreehari, traffic adviser to the government, warned that roads could cave in similarly all over the city, where the Metro underground network is passing through, if no proper care is taken.

The BMRCL should strengthen the soil all along the tunnels and underground corridors, he advised. The BMRCL should make pits at one metre intervals and fill them with cement and concrete which will help strengthen the soil and prevent further caving in, he said.

In the last few months, it is the second time that the road above the tunnel has caved in, causing inconvenience to the public. Many commuters on KG Road said that they were scared to go through roads where Metro tunnels have been built as such incidents can cost lives.

Ashok Kumar, an autorickshaw driver, said that the road collapsed when a garbage truck passed over it around 9.45 am. “The rear wheel of the truck got struck and 30 of us struggled hard to push the lorry out of the hole. We called up Upparpet police and BMRCL. The police came to the spot within 30 minutes, while BMRCL officials took over an hour. They immediately took precautionary measures,” he said.

The road over a Metro underground line caved in near Bhumika Theatre on Kempegowda Road, in Bengaluru on Tuesday (Photo: SHASHIDHAR B.)
The road over a Metro underground line caved in near Bhumika Theatre on Kempegowda Road, in Bengaluru on Tuesday (Photo: SHASHIDHAR B.)

A BWSSB engineer, who inspected the spot along with BMRCL officials, said that no sanitary or water pipeline was leaking under the road. “The caving in could be for a different reason,” he said.

BMRCL spokesman U.A. Vasanth Rao said that there could be many reasons for the collapse and that it was still a mystery. “A cavity could have been created when different civic agencies laid utilities under the road and that would have led to sinking of the earth,” he said.

“The Metro tunnel runs 45 feet below the surface. We have taken all precautionary measures to ensure the safety of Metro and road commuters. Instead of passing the buck, the BMRCL took the responsibility and filled the cavity. The caving in may occur elsewhere for various reason, but we cannot predict,” he said.

May happen again: Traffic expert
Traffic expert M.N. Sreehari warned that Tuesday’s caving in over the Metro underground tunnel is not a one-off case, and may happen again at different places if proper precautionary measures are not taken.

He told Deccan Chronicle that Metro tunnels may have weakened buildings and other structures above the ground because of vibrations. “If proper care is not taken to strengthen the soil around the tunnel, it may lead to disasters,” he said. In some stations, Metro roof is leaking. This is an indication that no proper water proofing has been done, he said.

All precautions taken: BMRCL
BMRCL spokesman U.A. Vasanth Rao said that adequate care has been taken while BMRCL dug the tunnels. Sensors were placed to check the vulnerability and to check the quantum of vibrations. “Wherever sensors showed deflections, we have either strengthened the structures or brought down weaker ones. The BMRCL issued notices wherever the structures are weak. But some have not allowed the BMRCL to demolish them at Chickpet and surrounding areas,” he said.

Major structures over Metro tunnels
Cubbon Park, Vidhana Soudha, Sir M. Visvesvaraya Building, Majestic (interchange station) and City Railway Stations are underground stations. Some of the major structures over the the tunnels are Bengaluru University, Cauvery Bhavan, Mysore Bank, Shikshakara bhavan, Alankar Plaza, Janata Bazar and others.