Combating Challenges with Innovations
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Combating Challenges with Innovations

MAHESH KUMAR elaborates upon the construction of the Nagpur Metro, overcoming myriad hurdles.According to a recent Oxford Economics Research Report (2018), Nagpur, which has a population of about 35 lakh, is currently the fifth fastest growing city in the world,...

MAHESH KUMAR elaborates upon the construction of the Nagpur Metro, overcoming myriad hurdles.According to a recent Oxford Economics Research Report (2018), Nagpur, which has a population of about 35 lakh, is currently the fifth fastest growing city in the world, with a projected average annual growth rate of 8.41 per cent between 2019 and 2035. Today, the city is largely dependent on personalised transport, with two-wheelers comprising 84 per cent of total vehicular share; the share of public transport (buses) is a miniscule 10 per cent. To eliminate the transportation woes of citizens, the Nagpur Metro Project was sanctioned on August 21, 2014 – the foundation stone was laid by the Prime Minister on the same day.Creating new milestones Designed to meet the needs and aspirations of all sections of the population, including the differently-abled, senior citizens, women and children, the Nagpur Metro has been aptly named ‘MaaziMetro’. Construction began on June 1, 2015, and the Maha-Metro team faced innumerable challenges right from the start. However, the team remained undaunted, going on to rapidly construct this 38.2-km, two-line signature infrastructure project with 38 stations and two depots, and to be operated with 69 state-of-the-art metro cars.In fact, Nagpur Metro’s physical progress has already exceeded 80 per cent – creating milestones along the way. The project has been the fastest to reach the trial run stage, within 27 months from the date of commencement of construction. Further, when its 13-km stretch from Khapri to Sitabuldi station was declared open by the Prime Minister on March 7, 2019, it became one of the fastest openings ever. Not to stand on its laurels, the team has further readied 11 km of viaduct and this section (Reach-3), when it opens to traffic in August 2019, is expected to set another benchmark in expeditious, quality construction within cost and time.Key challengesWhile the project as a whole was a daunting one for planners, designers, executioners and managers, the task of managing the execution in Reach-4 (Railway Station to Prajapati Nagar) along the crowded Central Avenue presented the most acute challenge as the Metro officials had to expedite the speed of work while ensuring the traffic remained undisturbed.Make no mistake; this is no ordinary road – with nearly 50,000 vehicles passing over it every day, this 17-km stretch has 17 busy junctions in one of the oldest parts of the city, dotted with commercial establishments and historical structures on both sides. At the beginning of the road was the 100-year-old bridge Ramjhula, which is currently being reconstructed after demolition a few years ago. Other landmarks include the Indira Gandhi Government Medical College and Hospital, frequented by thousands of patients every day, and the famed Poddareshwar Ram Mandir, a pilgrimage centre that organises the Shobha Yatra every year, a mega event witnessed by thousands of citizens. Constructing a metro-rail along such a busy road, while contending with the massive daily traffic, kept the engineers on their toes and impelled them to resort to innumerable innovations to ensure safe, fast and quality execution.Innovations employedCantilever pier arms and T-girders: Using precast T-girders ensures ultra-safe construction with minimum possible inconvenience to the public. As Reach-4 stations were to be constructed along the busy Central Avenue, prestressed pier arms with 10-m cantilever and adjoining precast T-girders were designed to support 22-m-wide and 77.50-m-long main station box structures instead of conventional cast-in-situ structures. The prestressed pier arms have been designed with two-stage stressing for optimum design benefits and precast T-girders arrangement, which eliminates the need for any ground support, resulting in safe and faster construction over the busy road underneath. Also, the T-girders are designed without any bearings, to substantially obviate maintenance hassles.Unique segment design and erection at Agarsen Square: The Reach-4 viaduct piers were positioned considering traffic study reports, future expansion of the roads and wider spans at road junctions. When the engineers came across the challenge of constructing a 43-m span at Agrasen Square, they designed the piers with extended pier caps of 3-m cantilever on either side. With this, they managed to eliminate a special-type superstructure and completed the work with a 37-m standard box-type viaduct structure without creating any problems for the traffic and the statue of Agrasen Maharaj underneath. Another challenge was the task of lifting segments as the lifting point of launching girder was exactly over the statue at the centre of the roundabout. Shifting the statue in the dense adjacent area was impossible as it would have resulted in thorough confusion, substantial delay and cost. The challenge was circumvented by employing alternative lifting methodology using Macalloy bars without disturbing the statue. Portal pier design to avoid utility diversions at Prajapati: Most of the Reach-4 metro alignment runs along the median, but alignment at a few locations needed deviation from the centre owing to sharp curves and interface with other structures. Construction near Prajapati section was one such difficult area where an NHAI flyover and subway are being constructed; this required the metro station to be designed such that it is adjacent to the flyover within a 24-m strip. Also, the metro viaduct at Prajapati section had to be integrated with the NHAI road flyover excluding Prajapati station and a few transition spans. However, during utility exploration at the location, engineers encountered many water pipelines exactly below the metro alignment. As most are main water lines, it was considered untenable to get diversion approvals or shutdown permissions. Thus, portal piers were designed to avoid utility diversions. This arrangement also enabled the station to be integrated with property development, with four levels eventually becoming accommodated, which in turn justified the cost incurred on portal pier construction. In fact, Prajapati Station is the only one with four levels, including two property developments, making it a unique structure. Second-largest balanced cantilever bridge: As a viaduct had to be installed above the rail line near Anand Talkies in the Sita Buldi area, the engineers proposed an innovative solution: A 231-m balanced cantilever bridge. Although this is not part of Central Avenue, executing this part of Reach-4. A three-span bridge with a configuration of 56.2 m + 103 m + 72 m and 103-m spans across the railway track, its complexity can be gauged by the fact that it is the second-largest span by balanced cantilever method across a railway line in India. Initially, it was proposed to use steel but a cantilever structure was chosen because it had a distinct advantage. Launching a steel truss requires intermediate support close to the railway tracks that necessitates piling, which is not feasible because of inadequate space between two tracks. This apart, erecting and launching a steel truss at a height of 16 m are high-risk activities. That said, even launching the balanced cantilever bridge was fraught with challenge as the location has a high density of railway and vehicular traffic and high safety standards had to be maintained. Also, constructing 16-m-high piers owing to the geographical profile was also problematic as the location is one of the busiest and most densely populated parts of the city, with movie theatres, hotels, commercial spots, a vegetable market and school.Overcoming every obstacleIndeed, there have been challenges aplenty, especially on Reach-4, but they have been overcome with alacrity and innovative thinking by the Maha Metro team. Cheers to them – and the city – for a smooth ride ahead!

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