Kolkata: Deep foundation by piling is necessary to construct any house that is more than five stories high in Kolkata, structural engineers told TOI. They also stressed the need for a proper gap between two adjacent buildings to prevent overlapping of the stress load each building exerts on the soil so that they don’t lead to foundation failure,
In Tangra, both these rules were violated, leading to the tilt in the buildings. The two buildings were six stories each, and they were constructed barely three feet apart.
Speaking to TOI, structural engineer Biswajit Som said conducting a soil test on the plot where a building will be constructed was crucial to identify the load-bearing capacity of the soil at various depths to determine the kind of foundation — deep or shallow — required for. the building that is proposed.
“In Kolkata, the soil is soft clay with poor load-bearing capacity. Unless a building is being constructed after demolishing an old building, any construction that is higher than four-five stories will require deep foundation or piling,” Som said.
His inference is drawn from a simple calculation. With the average soil in Kolkata able to take a load of 7 tonnes per square meter and the average load per floor at 1.5 tonnes per square meter, a two-storey building will apply a load of 3 tonnes per square meter, a three-storey building will apply 4.5 tonnes per square meter, a four-storey building will apply 6 tonnes per square meter, and a five-storey building will apply a load of 7.5 tonnes per square meter or the maximum limit.
Structural engineer Gokul Mondal also contended that soil in Kolkata does not have adequate strength till 14 m-15 m. He further pointed out that adequate distance between two high-rises was crucial to prevent a foundation failure.
“With two six-storey buildings constructed next to each other, there will be settlement of soil. That situation is further compounded by the lack of distance between the two buildings that has led to the creation of a pressure bulb with loads of the two buildings. overlapping on the soil. This will mean that the load at one point will be 14 tonnes per square meter. to soil settlement and foundation failure,” Mondal said.
In Tangra, both these rules were violated, leading to the tilt in the buildings. The two buildings were six stories each, and they were constructed barely three feet apart.
Speaking to TOI, structural engineer Biswajit Som said conducting a soil test on the plot where a building will be constructed was crucial to identify the load-bearing capacity of the soil at various depths to determine the kind of foundation — deep or shallow — required for. the building that is proposed.
“In Kolkata, the soil is soft clay with poor load-bearing capacity. Unless a building is being constructed after demolishing an old building, any construction that is higher than four-five stories will require deep foundation or piling,” Som said.
His inference is drawn from a simple calculation. With the average soil in Kolkata able to take a load of 7 tonnes per square meter and the average load per floor at 1.5 tonnes per square meter, a two-storey building will apply a load of 3 tonnes per square meter, a three-storey building will apply 4.5 tonnes per square meter, a four-storey building will apply 6 tonnes per square meter, and a five-storey building will apply a load of 7.5 tonnes per square meter or the maximum limit.
Structural engineer Gokul Mondal also contended that soil in Kolkata does not have adequate strength till 14 m-15 m. He further pointed out that adequate distance between two high-rises was crucial to prevent a foundation failure.
“With two six-storey buildings constructed next to each other, there will be settlement of soil. That situation is further compounded by the lack of distance between the two buildings that has led to the creation of a pressure bulb with loads of the two buildings. overlapping on the soil. This will mean that the load at one point will be 14 tonnes per square meter. to soil settlement and foundation failure,” Mondal said.