1,000-Tonne Concrete Boxes Pushed Under Rail Line as BDA Advances Challaghatta MAR Works

Bengaluru:

In a complex engineering operation seldom seen in the city, the Bengaluru Development Authority (BDA) is pushing ahead with construction of an eight-lane Multiple Access Road (MAR) at Challaghatta by inserting massive concrete box structures beneath the Bengaluru–Mysuru railway line.

BDA Commissioner Major P Manivannan detailed the precision-heavy, night-time effort in a social media post, calling it an “interesting engineering process” that demands flawless coordination between railway and road engineers.

According to the commissioner, the work involves temporarily cutting and removing a section of the railway track equal to the width of four lanes at a time. Once removed using a 750-tonne crane, the ballast and underlying soil are cleared and a temporary railway track mounted on a giant girder is installed. Trains—including high-speed services such as Vande Bharat—continue to run over this temporary track but at a restricted speed of 20 kmph for safety.

With the underside of the track fully exposed, four concrete boxes—each weighing over 1,000 tonnes—are slowly pushed beneath the railway line using hydraulic jacks. The operation progresses by roughly one metre a day, requiring around 30 days to complete the first four-lane stretch. After the boxes are fully inserted, the temporary track is removed, the original railway line is restored and welded, and normal load-bearing capacity is reinstated.

Once the rail line is secured, road formation begins inside the concrete boxes. The same process will then be repeated for the remaining four lanes, bringing the total construction time for the underpass to between 60 and 90 days. All work is undertaken only at night—between 11 pm and 4 am—when train traffic is minimal.

BDA Chairman NA Harris visited the site at night to motivate the teams.

The commissioner credited the South Western Railway for its “excellent support” in keeping the work on schedule.

Deputy Chief Minister D.K. Shivakumar has directed BDA to open the MAR to the public within the next three months, a target officials say is achievable if the momentum continues.