Pune: The execution of IIT-Bombay’s comprehensive slope stabilisation and rockfall mitigation plan for the Pune-Mumbai expressway’s Connecting Link is likely to be completed by Sept-end.Maharashtra State Road Development Corporation (MSRDC)’s joint managing director Rajesh Patil said nearly 15% of the recommended works had been completed despite the ongoing monsoon. “We have started the preliminary works. Once there are dry spells, construction will be expedited and we intend to complete all the recommended measures by September-end,” he said.The safety overhaul comes weeks after a landslide near one of the tunnel portals disrupted traffic on the newly inaugurated corridor on July 6. The landslide raised concerns over the project’s resilience during extreme weather events. IIT-Bombay was roped in to recommend measures to strengthen it.Based on the institution’s recommendations, the MSRDC is installing a combination of primary and secondary rockfall meshes, and permanent rockfall barriers, besides rock bolting. It has also initiated hydrological studies to redesign drainage channels and safely divert rainwater away from vulnerable slopes.Patil said, “Rockfall barriers will arrest any falling debris before it reaches the roadway, while improved drainage will reduce the slope instability during heavy rainfall.”He said the project was originally designed considering a one-in-100-year rainfall event. Around 670mm rainfall recorded on July 5-6 exceeded those design assumptions, prompting IIT-Bombay to recommend upgrading the protection measures to withstand a one-in-1,000-year rainfall event.Addressing concerns over the tunnel’s safety, Patil said the structure itself remained unaffected during the landslide. “Only the false frame at the tunnel entrance, which is an architectural feature and not part of the structural tunnel, was damaged,” he said.He said the command-and-control system installed along the Connecting Link enabled authorities to respond immediately after the landslide. “The upgraded safety measures are aimed at ensuring that no rockfall reaches the carriageway in future,” Patil said.The Connecting Link, inaugurated on May 1 (Maharashtra Day), is one of the state’s flagship infrastructure projects designed to bypass the accident-prone ghat section of Pune-Mumbai Expressway and reduce the travel time between the two cities. All the latest interventions and precautionary measures were intended to improve the corridor’s resilience against increasingly intense rainfall events, said another senior official of the MSRDC.IIT-Bombay recommended diversion of natural water flow and streams away from the top of the tunnels and vulnerable slope faces. Redesigning of natural surface drains and channels was suggested to prevent water from soaking into and weakening the hillside of the project.The institute advised to place high-tensile steel wire mesh and rock anchors to lock loose boulders and stones in place. Besides, cutting steep hill faces into stepped terraces to improve overall ground stability was recommended.
