The Maharashtra State Road Development Corporation (MSRDC) has stepped up safety measures along the Mumbai-Pune Expressway’s Missing Link after a landslide damaged the Mumbai-bound carriageway near a tunnel mouth in July.
The additional protection work, recommended by IIT Bombay, is being carried out above the tunnel entrances by contractor Navayuga Engineering Company Ltd. Around 50-60% of the work has been completed, with MSRDC targeting completion by the end of October.
The measures cover approximately 1.38 hectares of hillside and involve five key interventions: diverting newly formed water channels, removing loose and weathered rocks, installing steel rock anchors, fixing high-tensile wire mesh and erecting steel barriers to stop falling boulders.
Landslide Exposed Vulnerability
The latest work follows the July 6 landslide, when intense rainfall triggered large rocks to fall from the hillside near the mouth of the 8.9-km tunnel. Some boulders were estimated to weigh 17-20 tonnes and damaged the false frame at the tunnel entrance. Water emerging from the slope also flowed onto the Mumbai-bound carriageway.
The first focus has been on controlling water movement. Newly formed streams are being channelised and diverted away from the tunnel mouths after a hydrologist assessed the drainage requirements.
Unstable sections of the hillside are then being secured by removing loose rock and drilling steel anchors into stronger layers beneath the surface. High-tensile mesh is being placed over selected areas to contain smaller rocks, while steel barriers at different levels are intended to intercept larger boulders.
“Work on implementing these rockfall mitigation measures began immediately after the incident, but we’ve had to wait for dry spells in the monsoon to carry them out properly. By now, around 50 to 60 per cent of the work has been completed,” said Rajesh Patil, Vice Chairman and Joint Managing Director, MSRDC.
Stronger Safety Benchmark
After the incident, a team led by Professor D N Singh, a geotechnical engineer from IIT Bombay’s Department of Civil Engineering, assessed the slopes and recommended additional protection.
The Missing Link already had rockfall safeguards covering slopes up to around 15 metres above tunnel exits before its opening in May. However, the July landslide showed that higher sections could become vulnerable during extreme rainfall.
MSRDC has therefore adopted a stronger design benchmark for the new measures, with the reinforced areas being designed to withstand a 1-in-1,000-year weather event, compared with the original 1-in-100-year benchmark.
The 13.3-km Missing Link, built at a cost of Rs 6,695 crore, was developed as an alternative to the accident-prone Khandala ghat section of the Mumbai-Pune Expressway.
The immediate priority remains the hillside above the landslide-affected tunnel mouth, with similar protective measures planned above other tunnel entrances. The cost of the additional safety work is being assessed separately.
With construction progressing and October-end set as the target, the strengthened slope protection is expected to improve the resilience of the corridor during extreme weather events.
Source: The Indian Express
