In fact, the 4.5 km-long two-lane bidirectional tunnel, the longest on the Char Dham all-weather road project, had encountered a series of similar incidents in the past five years.Anshu Manish Khalkho, director (admin & finance) of the National Highways Infrastructure Development Corporation Ltd (NHIDCL), the PSU overseeing the project, told TOI on Thursday, “Around 19-20 minor to medium-level collapses occurred during the construction of the tunnel.”
Terming the collapses as “normal”, Khalko said, “Such incidents happen during every tunnel construction project but we were unlucky this time that workers got trapped.”
The collapses, also referred to as ‘cavities’, occurred on both the Silkyara side and the Barkot end of the tunnel, Khalkho said, adding that “more collapses occurred on the Barkot side than the Silkyara side”. He further said that an area of 160 to 260 meters (also called chainage) inside the mouth of the tunnel from Silkyara end was identified as a ‘red zone’ or a ‘shear zone’ having brittle rocks. “Additional protective measures will be taken to reinforce the area,” said Khalkho.
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Another official connected with the tunnel construction, preferring to remain anonymous, said that “the tunnel had faced numerous cavity collapses due to the challenging geology of the region and significant rock deformation”.
Notably, Bernard Gruppe, an European company that is providing design services to Navayuga Engineering, the construction firm that has got the contract for the tunnel construction, had earlier said that “geological conditions (at the tunnel site) proved to be more challenging than predicted in the tender documents”.
