A truck moves up the flyover despite the no-entry sign put up by police and the CMC

Goods-laden trucks have been plying on the Dhakuria flyover despite a ban on heavy goods vehicles since July when a portion of the 50-year-old structure’s walkway gave way.

The unhindered movement of trucks could lead to serious cave-ins because the flyover, unlike modern constructions, does not stand on piers but mounds of earth with a gradual inclination from both ends, engineers said.

The earth-filled surface, reinforced by thick concrete walls, is infested with rats that have burrowed a network of tunnels and thereby weakened the structure.

“There is empty space beneath the flyover, making the structure vulnerable when a heavy vehicle plies above. The gaps cannot withstand the load of a laden truck,” said D.C. Mitra, the project co-ordinator of Rites. The railway subsidiary, Rites, has been given the responsibility of fixing the flyover.

Another lorry plies on the flyover

Metro spent an hour on the flyover from 10.40pm on Thursday. About four large vehicles crossed the flyover in a span of five minutes. Policemen manning barricades at both ends made no attempt to stop the vehicles.

“The trucks move at such high speed that it is difficult for us to stop them. Had there been a few more men, I would have stopped them,” said a policeman who was noting down the registration numbers of a few lorries.

03dhakuria-bridge-july

The Metro report on June 12 about the cave-in on the Dhakuria flyover walkway

In fact, bold signage at the Golpark crossing and another one at the northern end of the flyover announce the ban but to no avail.

The 1960-built Dhakuria flyover is among the earliest concrete overbridges in the city and has outlived its use-by date. A concrete flyover is meant to retire after 50 years.

“Rat holes and the natural sinking process of the earth filling have created large holes under the flyover. We can’t see them from above but they are there. Which is why heavy vehicles have been barred to reduce the risk of cave-in,” the engineer said.

A laden lorry weighs between 12tonne and 20tonne while a bus can be eight to 10tonne. Considering the difference in weight displacement, the Calcutta Municipal Corporation (CMC) didn’t ban the movement of buses.

The deputy commissioner of police (traffic), Dilip Adak, promised to beef up checks. “I wasn’t aware of the trucks plying on the flyover. I will ensure that the checks are foolproof,” he said.

Rites has devised a technique to strengthen the perilous structure. “We are preparing a slurry with cement, fly ash and a chemical. We will inject the mixture under high pressure through holes in the walls to fill up the gaps,” Mitra said.

Labourers work to fix the the hole. Pictures by Pradip Sanyal

The next step will be to scrape off the top layer of the surface and run a vibrating roller that will let the slurry settle evenly. “The roller will exert pressure as well. Once it is done, we will rebuild the top layer,” Mitra added.

The repairs are likely to be over by next month.

The cave-in had created a 1.5ft gap in the 4ft-wide elevated walkway at the AMRI hospital end. A police patrol had noticed the damage and put a guard-rail to seal the area for pedestrians.