The Rs 6,695-crore project, undertaken by the Maharashtra State Road Development Corporation (MSRDC), boasts of several records, including the world’s widest twin tunnels, spanning 47 metres over 10 lanes, a fact recognized by Guinness World Records. The daylighting process for the tunnels, in two stretches of 8.9km and 1.7km, has been completed. The remaining task involves bridging the 650-metre gap between them with the country’s tallest cable-stayed road link, being constructed in the scenic Tiger Valley of the weekend getaway Lonavala. The construction of pylons, with an average height of 132 metres, and a maximum height of 182 metres, and connecting pillars for the bridge are in their final stages, said Rahul Vasaikar, the project’s superintending engineer.
The 12.1km Missing Link project aims to bypass the Expressway’s 19km Khandala ghat section, reducing the distance between Mumbai and Pune by over 6km and travel time by nearly 30 minutes. This reduction will result in significant fuel and carbon savings, as the ghat section burns fuel because of ascent and traffic congestion. Although the Expressway’s toll structure will not change, motorists will have to pay it for 15 years beyond the existing toll contract period, which was scheduled to end in 2030.
When other planned or under-construction augmentation projects are added to the Missing Link, the travel time between Mumbai and Pune will cumulatively reduce by almost 90 minutes. These projects are: Shedung-Palaspe link (across the junction of the old Pune highway and the Expressway), three flyovers between Palaspe and Chirle, the MTHL and the Sewri-Worli connector. Once all these projects are commissioned, it will be possible to drive from Worli in Mumbai to Koregaon Park in Pune in no more than 90 minutes, whereas currently it takes almost four hours in daytime traffic.
Anil Gaikwad, joint MD, MSRDC, said setbacks caused by Covid led to a delay of 22 months. Despite operating with reduced staff during that time, the team’s efforts over the past year have ensured that the project will be completed by the middle of next year, instead of the earlier estimated timeline of 2024-end. Construction work on the Missing Link is 71% over, with tunnel works reaching the 90% mark. Afcons, a prominent infrastructure company, is responsible for building the bridge section, while Navayuga Engineering, another infrastructure giant, has undertaken tunnel construction.
In addition to the tunnel-bridge section, the six-lane Expressway is planned to be expanded to accommodate two extra lanes on each side, creating an eight-lane expressway to match the width of the tunnels and bridges under construction. “Widening between Sinhagad Institute towards Pune and Khalapur toll post towards Mumbai, along with the creation of approach roads, slip roads, and related works, is in progress,” said MSRDC executive engineer Rakesh Sonawane.
The project has employed jump formwork technology (a special type of climbing mould used to make vertical concrete structures) for the pylons of the cable-stayed bridge. This technology allows for concurrent construction of the vertical and horizontal parts of a structure, reducing costs and improving construction speed. For the tunnels, controlled blasting has been used instead of tunnel boring machines (TBMs), due to the Austrian blasting method’s superior speed and cost-effectiveness. Controlled blasting allows for the excavation of about four metres of tunnel with just one blast, while the efficiency of a TBM is only 50%, making it slower and more expensive. Since the Lonavala hills are not densely populated, the use of controlled blasting was deemed appropriate by MSRDC.
The tunnel section will feature a sensor-based automated water mist system to extinguish fires or maintain safety if the temperature inside reaches 65°C. Additionally, there will be 24×7 SCADA (supervisory control and data acquisition) monitoring for commuter safety. Cellphone and FM signals will be received even in the deepest sections of the tunnels. An advanced ventilation system, a public address system for emergency announcements and traffic direction, and diesel generators providing continuous power supply for lighting and other facilities will be installed.
Safety will of utmost importance for the 8.9km section of the second tunnel stretch, officials said. The tunnels will have evacuation joints that internally connect the parallel tunnels every 300 metres, providing around 28 evacuation shafts for vehicles in case of major jams or accidents, ensuring enhanced safety for commuters.