Meeting challenges through innovations, the Maha Metro way
Maha Metro aims at constructing 38.215 km long track along 38 stations and connecting four corners of the city of nagpur. But executing the project work was easier said than done. Maha Metro had to face a number of challenges while doing so.
while challenges were universal across city, executing the project work on Central Avenue – a crowded road with commercial spots on either side – turned out to be Organization’s toughest task. The work in this stretch, which is part of Reach-iv in Metro parlance, starts near Railway Station and ends at Prajapati Nagar.
Central Avenue is one of most crowded roads of the city with commercial spots lined on either sides for almost the entire stretch. So while executing project Maha Metro Nagpur had to ensure that not only traffic there remained undisturbed, but also the speed of work remains same. The gravity of traffic congestion on Central Avenue can be gauged from the fact that as many as 45,000 vehicles pass through this 17 km long road every day. It has 17 traffic junctions and is one of the oldest part of city with historic structures lined up on its either sides. Some major innovations and their effective use by Maha Metro were:
• Psc cantilever pier arms and t-girders
As, reach 4 stations are to be built over the busy Central Avenue, pre-stressed pier arms with 10m cantilever and precast T-girders adjoining each other have been designed to support 22m wide and 77.50m long main station box structures instead of conventional cast-in-situ structure. The Pre-stressed pier arms have been designed with 2 stage stressing to have optimum design benefits and precast T-girders arrangement, which eliminates necessity of any ground supports, which in turn resulted safe and faster construction over the busy road underneath. Also, the T-girders are designed without any bearings, so that maintenance hassles could be evaded.
• Unique segment design and erection at agarsensquare
During the course of design, we come across the challenge of constructing 43m span at Agrasen square and our design team was up for the challenge. Accordingly Piers were designed with extended pier caps of 3 m cantilever on either side. With this design we could eliminate special type super structure and managed to complete with 37m standard box type viaduct structure without disturbing traffic and statue underneath. Subsequently, we had to overcome another construction challenge of lifting segments as lifting point of launching girder was exactly over the statue of Agrasen Maharaj located at the centre of round about and necessitating relocation of statue. But, shifting of the statue is a complex issue and thus it was decided to use macalloy bars without disturbing the statue, saving a lot of time and cost.
Maha Metro or Maharashtra Metro Rail Corporation Limited launched its Nagpur project as a serious effort aimed at ending transportation related woes of Nagpur – the second capital of Maharashtra which has a bustling population of close to 3.5 million.
• Portal Pier design to avoid Utility diversion at Prajapati
As NHAI flyover and subway are being constructed at Prajapati section, metro alignment needs to be designed adjacent to NHAI flyover within 24m strip. Also, Metro viaduct at Prajapati section is integrated with NHAI road flyover excluding Prajapati station and few transition spans. However, during utility exploration at Prajapati station location, we found that many water pipelines including pressure pipe supplying water to power plant and bunch of drinking water pipe lines were located exactly below metro alignment. Since most of the pipelines are main water lines, it is very difficult to get the diversion approvals from the authorities or the shutdown permissions as it involves many regulations and lengthy process. Therefore, Prajapati station was designed with Portal piers arrangement, which in turn proved to be ideal design as Prajapati station is integrated with Property development and eventually four levels could be accommodated, which in turn justifies the cost incurred on portal pier construction. Prajapati station being an only metro station with 4 levels, including 2 PD levels stands out from all the rest.
• second largest Balanced cantilever Bridge to be installed
Though this is not part of Central Avenue, executing this part of project was equally tough. Viaduct had to be installed above rail line near Anand Talkies in Sitabuldi area of Reach-iv. A 231 meter long Balanced Cantilever Bridge was proposed to be installed above Railway Track near Anand Talkies, Sitabuldi of Reach-iv. Metro team decided to use Balanced Cantilever Bridge there. But even launching of Balanced Cantilever Bridge is a challenging task as the location where the bridge is supposed to be erected has class “A” traffic (high density) and a live railway traffic. Also height of Piers as high as 16 meters due to geographical profile is also a challenge in itself. Also, the location – Anand Talkies, Sitabuldi is a high population density zone. The proposed Cantilever is a 3 span bridge with spanning configuration of 56.2m + 103m + 72m, 103m span across railway track. It is second largest span by Balanced Cantilever method across the railway lines in India.