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Indian cities are among the world?s fastest developing cities in terms of every aspect: growing population, economy, infrastructure and most importantly traffic. The transport system of India is shifting from private modes of conveyance to a new mode of public transport called metro. Kolkata was the first city to get rapid transit system in India put in motion almost 25 years ago. Chennai is second city in India to run a rapid transit system in 1995, Chennai mass rapid transit system is an elevated railway line running within the city. The next inline was Delhi metro rail running across the national capital region. Currently, metro rail projects are running in various parts of the country. After the success of the Delhi metro, 26 cities in the country are at various stages of planning and implementing the metro rail.

Concreting the metros
Metro projects consist of various concrete structures and types, which are considered to be a very challenging. Majority of construction work in a metro project is differentiated into elevated corridor structures, elevated railway stations, underground tunnel construction, underground railway station, and underground to elevated interlinking junctions.

Metro elevated corridors (Viaduct) are meticulously designed structures developed with understanding of high strength concrete. The elevated structures consist of precast segment made using special type of concrete. The state-of-the-art construction methods help to make pre-cast and pre-stressed concrete segments. These segments are of different types like box girder segment, spine, wings, single segmental U, single segmental box, segmental box, segmental U, full U girder, pre-cast pre-stress I girders, cast in situ span, and special span.

Elevated metro stations are also concreted using pre-casted segments. These pre-casted segments are prepared by casting concrete in reusable moulds in a controlled environment. Then it is transported to construction site and set in place. Some of the pre-cast structures used in elevated metro stations are platform sections, precast post-tensioned cross girders and pre-cast post-tensioned L-beams. The elevated corridor also requires concrete pile cap, pier and cross heads (cast in situ/pre-cast pier heads).

Underground tunnel construction is carried out using tunnel boring machines (TBMs) which not only excavates the tunnel but also installs precast concrete liners (tunnel rings). As the machine advances inside the earth through movement drilling, both the ground in front of the machine and the horizontal ?hole? it creates are continually supported by TBM shield and pre-cast concrete tunnel liners that are installed as the machine progresses. This method creates a tunnel with little or no disruption at the surface, and is especially suitable for creating a circular opening at greater depths than would be practical for cut-and-cover construction. The concrete tunnel liner segments will have rubber gaskets between them to prevent water from entering the tunnel, and also allows the excavation to advance below the groundwater level. The pre-casted tunnel rings are also made of special type of concrete which are designed to withhold the underground environment.

Schwing at metro projects
Schwing Stetter India had an opportunity to be a part of many of the metro rail projects in India that tested the caliber of its equipment. Schwing Stetter?s batching plants like CP30 and M1 were used for per-casting various segments for the elevated corridors. Schwing truck-mounted boom pumps S20 and S36 are used for concreting the pile cap, pier and cross heads. Schwing machines are used for pre-casting tunnel rings and its concrete trailer pumps are used to concrete the floor inside the tunnel to lay tracks for metro trains. In most of the concreting site where such type of concreting is done with Schwing pumps deliver the concrete from starting to end point of the tunnel.

Underground metro stations are constructed using massive amount of concrete in which Schwing contribution is enormous. Underground stations are constructed using cut-and-cover methods in two different ways ?top-down? or ?bottoms-up? approach. For the underground stations, diaphragm walls and plunge columns are constructed to ensure that soil does not collapse on the edges as the excavation progresses. The construction of the diaphragm wall is carried out from ground level using special type of concrete; Schwing transit mixers are used to transport concrete for the construction of these walls.

With service and spares support across the country and a customer centric manufacturing facility, Schwing mission and vision is customer satisfaction. A customised solution provider and a brand known for high quality and prompt after sales support, Schwing Stetter India has been rated as the best take in the market for providing solutions pertaining to the concreting industry.