RailEnquiry

Crack not due to underground work, but routine inspections a must, say experts. Structural engineers have a word of caution for Chennai Metro Rail Limited (CMRL) and LIC in the report on the cause of the crack observed on the 11 floor of the iconic building on Anna Salai.While LIC has been asked to hold inspections periodically, CMRL has been asked to conduct tests to ensure safety.Ruling out metro rail work as the cause of the crack, the report recommends that repair works be initiated immediately, and that LIC carry out inspection once in five years to ensure the structure is effectively maintained.Experts in structural engineering have also recommended that CMRL, on its part, take up relevant tests to ensure the desired strength and durability of the reinforced underground concrete diaphragm wall. This is because they suspect the operation of the vibro hammer resulted in damage to the reinforced concrete diaphragm wall.Since the LIC building is asymmetrical, the exterior wall needed to be inspected to check the pattern of cracks, and the depth of the cracks had to be ascertained. Following that, suitable repair methodology can be proposed to seal the cracks, the report said.On July 11, a crack was observed on the 11 floor of the LIC building. Then, engineers at LIC attributed it to the ongoing metro rail construction work at the underground station site near the buildings.

After LIC wrote to CMRL raising concerns about the construction work and potential risk to their building, professors R. Sundaravadivelu and Ravindra Gettu from IIT-Madras inspected the crack in the presence of engineers of LIC, CMRL and the contractor, Gammon.

Following inspection, the committee submitted a three-page report to CMRL on August 10. According to the report, the LIC building is safe.

“Most of the presently-visible cracks existed in the building prior to the operation of vibro hammers in June and July 2012, as they have been patched up and painted on. However, no records of previous repair work are available to ascertain the exact intervention that was made in the past,” the report said.

“The subsequent opening of these cracks over part of their length appears to be structural actions which could include the vibrations experienced by the shear walls during the operation of vibro hammers,” the report said, adding: “The cracks pose no immediate danger to the building.”

According to officials of CMRL, vibro hammers are indispensible in underground metro rail construction work of this nature.

However, they emphasise that necessary precautions are in place to ensure that no building in close proximity to any of the construction sites is in danger.