Anatomy of a correction surgery to straighten building gone wrong
Times of India | 16 January 2025
12 Kolkata: A day after the tilting of a four-storey building near Baghajatin, structural engineers blamed the unscientific and crude methods employed by the Haryana-based firm. They called for immediate curbs on such non-engineering rectification attempts to prevent a recurrence of such disasters.
"The building may have leaned due to soil settlement, but I believe that, like many leaning buildings in Kolkata, Salt Lake, and New Town, this building would also have survived for decades if attempts had not been made to straighten it using dubious methods," structural engineer Biswajit Som said.
Gokul Mondal, another structural engineer, recalled an intervention in Salt Lake eight years ago when a similar misadventure to straighten a leaning building was stopped through Salt Lake municipality.
In Kolkata, there are multiple leaning high-rises on Camac Street, Theatre Road, and JL Nehru Road that have a pronounced tilt, but residents have continued to live in them for decades. In New Town and Salt Lake, too, there are several buildings that have tilted due to soil settlement.
Mondal said the thick layer of soft alluvial soil leads to settlement unless the foundation is strong and the building's weight distribution is even. While soil investigation is required before construction, the expert doubted if the protocol was followed in this case.
Underpinning, a corrective measure used to rectify tilts, is prohibitively expensive in smaller buildings. It involves excavation around the existing piles and insertion of underpinning piles before placing jacks to lift the building and transferring the load on the foundation of the new underpins. Instead, the agency appears to have placed the jacks below the walls to straighten the building and not under the foundation beam. Also, no effort seems to have been taken to strengthen the base on which the jacks were placed.
"When the building initially tilted, the load on the soil from the wall was distributed. When jacks were placed, the load got concentrated. That would have caused the soil to settle again. This would make the building tilt further and cause immense stress on beams and columns, leading to cracks and ultimately structural stability failure. This is what appears to have happened," Som pointed out.
A viral video seems to indicate that while jacks were applying pressure to lift the building, cracks appeared on the first-floor wall, column and lintel level next to a large opening. A few seconds later, the building collapsed. "It could have been due to the settlement of one or more jacks or weakness in the structure that was unable to absorb the minor movement caused by the attempt to lift the building," he added.