The National High Speed Rail Corporation Limited (NHSRCL) on Thursday (28 October) started the casting of the first full span Pre-Stressed Concrete (PSC) box girder of 40 metre span to expedite the construction of viaduct for Mumbai- Ahmedabad High Speed Rail corridor (MAHSR), in a casting yard in Anand, Gujarat.
PSC Box Girder of 40 m span weighs around 970 metric tonne (MT) and will be the heaviest PSC Box Girder in the construction industry of India, the Ministry of Railways said in a statement on Friday (29 October).
The 40 m span Girder is being cast in a single piece i.e. without any construction joint, involving 390 cubic metre of concrete and 42 MT of steel, the ministry said.
Mumbai-Ahmedabad High-Speed Rail Project is 508 km long and out of the total length of the project, 352 Km lies in the state of Gujarat (348 Km) and Dadra and Nagar Haveli (4 Km), and the balance 156 Km lies in the state of Maharashtra. Out of 352 Km length in Gujarat, L&T is the executing agency for 325 Km length.
According to the ministry, to expedite construction of viaduct, construction of substructure and superstructure has been taken up in parallel.
While the work of substructure i.e. Pile, Pile Cap, Pier and Pier Cap, is in progress, for superstructure, casting yards have been developed along the alignment to cast Full Span Girders and Segmental Girders so that they can be launched using heavy machinery over casted Pier Cap, it added.
For casting of Girders, twenty-three casting yards are being developed along the alignment. Each casting yard is spread in an area of 16-93 acres as per requirement and is located near to the alignment.
For expeditious casting of Girders with quality, facilities like jigs for making Rebar cage, Casting Beds with Hydraulically Operated Pre-Fabricated Moulds, Batching Plants, Aggregate stacking area, Cement Silos, and Labour Camps have been developed in each casting yard, the ministry said.
Most of the Girders will be of Full Span 30, 35 and 40 m, however, for locations having site constraint, segmental launching of small precast segments will be used.
Full Span Girder are preferred over Segmental Girder as their launching progress is seven times faster.
These Precast Girders will be launched using heavy machinery like Straddle Carrier, Bridge Gantry, Transporter and Launching Gantry.
To ensure the continuous supply of girders for launching, the Girders will be cast in these casting yards in advance and stacked in a systematic manner.
The Straddle Carrier will pick the Box Girder from the stacking yard and will feed to the Bridge Gantry, which in turn will lift the Box Girder and place it over the bearing on Pier Cap.
Bridge gantry will launch first 3-4 Box Girder, on which Girder Transporter will be placed and further launching of Girders in sequential manner will continue using Transporter and Launching Gantry.
Planning of casting yards and heavy machinery for launching has been done in such a way so as to meet peak requirement of approximately 300 Full Span Box Girder Casting and Launching in a month, which equals to approx 12 Km of superstructure casting and erection in a month.
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