130 tonnes concrete used to fill Anna Salai crater

Chennai: TIMES NEWS NETWORK





Around 130 tonnes of concrete have been used to fill the sinkhole that appeared on Anna Salai, near thr Gemini flyover, earlier this month due to metro rail construction. The traffic flow on the damaged stretch will be restored in about 10 days as metro rail will remove the metal sheets placed on the surface.

“The crater is spread over 130 cubic metres. For every cubic metre, we needed one tonne grout. So far, we have filled the crater with about 130 tonnes of concrete. But we keep grouting in the area post midnight, so we may use more concrete,“ a metro rail official said. “We will remove the existing metal sheets in about 10 days once we confirm that the crater is completely filled with concrete, compacted and packs the aggregate is set and hardened.“ The road had caved in on pril 9, when metro rail engi April 9, when metro rail engineers were building tunnels underground, trapping an MTC bus carrying 35 passengers and a car. The incident created a crater of 10 feet wide and 15 feet deep.Chennai Metro Rail Ltd (Cmrl) claimed it was due to loose soil below the road surface. Officials said they had be grouting -filling the cra en grouting -filling the crater with fluid form of concrete -daily since the cave-in. A team of metro rail workers have been permanently deputed to keep a tab on soil settlement once in six hours.Settlement markers had already been installed on the road along the alignment of the tunnels being built for the purpose. The team also fills fluid concrete in the entire area under the road and looks for any cracks that may develop due to concrete setting.

Soon after the incident, Cmrl workers began filling the crater with grout. They also dug nearby spots to check for similar cavities and fill them with concrete.The entire area was sealed with metal sheets. A concrete mixer has been permanently placed on the pave ment nearby for grouting every night. “We have also filled the cracks that developed when the concrete began hardening. We are also ensuring that no more cracks develop as the concrete sets,“ an official said.

But the placement of metal sheets to cover the concrete filling posed a problem for traffic movement. Motorists have had to slow down as they neared the spot and it leads to traffic piling up frequently. It also posed a risk of road accidents as the metal sheets sealed to the road with liquid cement came off and workers had to repeatedly pour cement to seal them.

“Our tunnel boring machines have moved ahead from the location where the road caved in. About 15 metres from ther cave-in spot the soil is completely rocky. So, the chances of cave-ins are slim,“ the official said.