Our team kept challenging itself and achieved significant milestones

Our team kept challenging itself and achieved significant milestones

Please take us through the iconic project’s timeline since inception. The timely completion of such a mega project has been achieved by L&T despite challenges like adverse climatic conditions and the COVID-19 pandemic, which disrupted our global supply chain and availability of wor...

Please take us through the iconic project’s timeline since inception. The timely completion of such a mega project has been achieved by L&T despite challenges like adverse climatic conditions and the COVID-19 pandemic, which disrupted our global supply chain and availability of workforce. Since inception, the project team kept challenging itself and achieved significant milestones. Starting with the pile foundation works in 2018, the team began the first superstructure concrete span erection works in February 2020. Tell us about orthotropic steel deck (OSD) technology. A first-of-its-kind engineering feat in India, OSD span erection works began in January 2022 and about 38 OSD spans (85 to 180 m) were erected within a challenging 15 months, including three non-working months in the monsoon. Its features are: Efficient use of materials, optimising distribution of steel in the structure. Low self-weight compared to concrete and composite structures with better resistance to seismic and wind forces Fabricated and assembled in a controlled environment –assuring safety during construction and adherence to quality requirements Elimination of requirement of high pylons, reducing the risk of working at extreme heights Safeguarding the flight path of flamingos, ensuring minimal disruption to natural patterns. What materials, techniques and technologies went into India’s longest bridge? Some noteworthy materials, techniques and technologies are: 51,444 mt of high tensile strength steel conforming to Japanese standards used in OSD fabrication 95,000 mt fusion-bonded epoxy-coated rebar and rebar with Fe500 and Fe550D grade as reinforcement in structures for concrete reinforcement 10,000 mt zinc-coated, wax-filled, HDPE co-extruded strands and flow-filled epoxy-coated HT strands for prestressing of concrete spans High-strength concrete with a chloride migration coefficient value of < 2 x 10-12 m2/s, providing durability and resistance to environmental factors 660 reinforced masonry (RM) of longitudinal expansion joints connect with the existing bridge span of the Eastern Freeway 608 elastomeric bearings for large concrete spans (up to 1,150×1150×341mm) 459 spherical bearings for approach spans 92 pot bridge bearings for controlled movement and flexibility in the bridge structure, adapting to various loads and dynamic conditions 108 tune mass dampeners (TMD) for OSD bridge girders Many technologies were implemented for the first time in the country, OSD being one of the most crucial. L&T deployed an OSD expert onsite for knowledge transfer at every stage and developed in-house methodologies for assembly and erection activities. Will the foundations hold the bridge for generations to come? The structural integrity of the bridge is ensured through a robust foundation designed to withstand the test of time. A rigorous multimodal seismic analysis using a site-specific response spectrum has been carried out for design of the substructure. In-depth underwater surveys were conducted to ascertain that the foundations do not interfere with existing underground utilities. Based on survey findings, the foundation designs were adjusted to ensure compatibility and avoid any adverse impact on existing infrastructure. The foundation piles of 2.2 m diameter were designed to carry their load by friction and end-bearing and are founded in the hard rock, reaching up to 47 m below water level. The piles are anchored firmly into the hard rock with anchoring of six times the diameter of piles, i.e., 13.2 m. High-strength M45 and M55 grade concrete was used to ensure durability and strength of the foundation, providing a resilient support system for the bridge. Integrity of all the piles was ensured through cross-hole sonic logging. Kindly elaborate upon the engineering and marine construction challenges. This part of the Mumbai coast is also home to some fishing villages, a power plant, oil refineries and other sensitive installations. There is also a dedicated shipping channel to Nava Sheva port. The engineering, therefore, had to take into consideration construction that would least disturb subsea facilities like gas pipelines, HT cables, loading jetty, coal handling jetty and other facilities. These constraints imposed restrictions on span configuration and bridge deck types in design. The project involved many international engineering organisations and efficient coordination between them resulted in effective design implementation on the site. Some marine construction challenges were: Logistics: A major challenge in marine construction was travel time in boats of about three to four hours on a daily basis to reach the work location, which disrupted productive time available and also ensuring labour welfare and medical assistance on call to create a healthy and safe working environment. We had to identify a nearby jetty for marine operations and control to reduce logistical challenges. To ensure round-the-clock productive work, the shifts were increased from two to three. Severe climatic conditions: Working in a marine environment came with a challenge of managing work while tackling high winds, tidal variations, sea-sickness, extended monsoons and the threat of cyclones. A dedicated weather intelligence agency was deployed for precise weather forecasting, enabling meticulous planning of activities and movement in the sea. Skill of workforce: We had workmen having limited or no experience of working in marine conditions at heights up to 27 m above water level. We had to set up multiple training centres within the project site to train and enhance the skills of staff and workmen with domain experts. Up to 120 workmen were trained per day. The project has developed a competent workforce for marine projects of similar requirements.  Please tell us about future connectivity plans. On the Mumbai side, the Sewri interchange already connects to the existing Eastern Freeway and Messant Road at Sewri. Additionally, two ramps are under construction to provide connectivity to Worli via the Sewri Worli elevated corridor. The upcoming Orange Gate underground tunnel project of MMRDA, awarded to L&T, will further enhance connectivity of MTHL-Eastern Freeway to the Mumbai Coastal Road. On the Navi Mumbai side, the proposed Chirle-Palaspe elevated corridor further improves connectivity to the Mumbai-Pune Expressway, bringing Goa and Pune closer for motorists. The Shivajinagar interchange is strategically positioned to link MTHL to the under-construction Navi Mumbai International Airport and Jawaharlal Nehru Port Trust (JNPT), besides local roads. - R SRINIVASAN

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