River Narmada – The Fifth Largest In The Country
It comprises of 30 Major Dams, 135 Medium Dams and around 3,000 Minor Dams along the 1,312 km length.
Sardar Sarovar Dam
It is a concrete gravity dam across river Narmada
Length - 1210 meters (3970 feet)
Maximum height - 163 meters above the deepest foundation level, is constructed upto the crest level of spillway i.e. 121.92 m.
Third highest concrete dam (163 meters) in India
First - Bhakra (226 metres) in Himachal Pradesh
Second - Lakhwar (192 meters) in Uttar Pradesh
Achievements in the design and execution
River Diversion Scheme,
Submersible Cofferdams under flowing water conditions across deep river channel,
Excavation of open cut diversion channel,
Providing gated construction sluices etc.
Treatment of geological fault
Treatment of geological fault in the dam foundation involved-
2,14,000 m³ of excavation,
2,50,000 m³ of rock excavation,
2,56,000 m³ of pre-cooled concrete
53,000 tonnes of reinforcement steel.
Treatment of argillaceous sandstone
Treatment of argillaceous sandstone in two layers on the right bank and red bole layer on the left bank was carried out by providing a grid of concrete shear keys (3.0 m wide and 3.5 m deep) parallel and perpendicular to the dam axis aggregating to 12 km length.
With such a vigorous treatment, the design of the dam allows for a horizontal seismic coefficient of 0.125g.
It also covers an additional risk due to reservoir induced seismicity.
Thus foundation treatment itself was more challenging than construction of any major dam even!
In terms of the volume of concrete involved for gravity dams, this dam will be ranking as the second largest in the world.
Second largest in the world- With an aggregate volume of 6.82 million m³.
The first is Grand Coule Dam in USA with a total volume of 8.0 million m³.
Longest in the world
Two Cable Cranes used for placing the concrete were the longest ever in the world.
Each having -
Capacity - 28 ton capacity
Spanning - more than 1.5 km
Third in the world
This dam with its spillway discharging capacity of
87,000 m3 /second (30.70 lac), will be the third in the world,
First - Gazenba (1,13,000 m3 /second) in China and
Second -Tucurri (1,00,000 m3 /second) in Brazil
World’s largest concrete lined canal
The Narmada Main Canal, having a length of 458 km in Gujarat and further extended to 74 km in Rajasthan, is world’s largest concrete lined canal
Discharge carrying capacity - 1133 m³/second (40,000 cusecs) at its head.
This unique canal is a contour canal having command area of 18,45,000 hectare on its left bank.
634 structures are constructed
Along its length of 458 km i.e. upto Gujarat-Rajasthan border, total 634 structures are constructed of which
114 are control structures (Head Regulators, Cross-regulators and Escapes)
231 are crossdrainage works for crossing natural streams and other canals (Aqueducts, Syphon Aqueducts, Canal Syphons, Drainage Syphons and Superpassage) and
289 structures are communication structures (Road and Railway Bridges).
Magnificent construction structures
Some of the structures on Narmada Main Canal are magnificent from the size, technical complexity, design and construction points of view.
Noteworthy structures include -
Watrak Canal Syphon,
Sabarmati Canal Syphon,
Escape structure on river Sabarmati,
YJunction (offtake point of Saurashtra Branch Canal),
Banas Canal Syphon,
Saraswati Canal Syphon etc.
Range of design challenges and their safe and economical solutions
The range of design challenges involved in these structures included -
high discharges leading to larger barrel size,
typical foundation problems,
long-term consolidation settlement,
design of leak-proof joints at the locations vulnerable to differential settlement,
seismic factors and dynamic response of the structure,
magnitude of fall,
limitation of the available materials and products (for example bearings) etc.
for which readily available solutions were not present.
State of the art technology including mathematical and physical model studies was harnessed to arrive at the safe and yet economical solutions.
Various research institutions of national and international repute were also consulted to resolve many such issues.
From construction point of view -
mechanized paver lining on side slopes,
dewatering on major river crossings,
slip formwork for speedy construction etc.
were the pioneering efforts made in the construction history of the whole country.
World’s largest Aqueduct on river Mahi
Constructed for - Mahi Aqueduct constructed for crossing the River Mahi at NMC Ch. 142.86 km.
Length - 602.5 m
Size - It contains 8 Barrels of Size 6.10 m x 7.6 m.
Concrete - Total 387 Thousand m3 concrete was poured
Steel - 22904 tonne steel was consumed for completion of the structure
Time duration - Took more than 9 years!
Total concrete volume used in this structure alone is more than that used in the Burj Dubai – the world’s tallest tower (3,30,000 m³).
Saurashtra Branch Canal
There are 38 branch canals offtaking from NMC to serve a vast command of 1.8 million hectares spread in 15 districts.
The largest of these is Saurashtra Branch Canal which has a
Length - 104.46 km and
Discharge - 424.80 m³ /second.
To negotiate the peculiar land topography,
With a falling ground from Ch.0.0 to 59.0 Km by about 52.0 m
Thereafter from 59.0 to 104.460 Km a rising ground by about 66.0 m
before tailing into Bhogavo - II reservoir,
Three power stations at fall points and five pumping stations at lift points are planned.
Total 48 MW hydro power is planned to be generated at the three fall structures at Ch. 5.15 km, 17.76 km and 32.94 m each having a vertical drop of 10.9 m.
Thereafter total lift of 71 m is provided by a series of five Pumping Stations at Ch. 66.518 km, 77.165 km, 87.95 km, 93.205 km and 102.84 km with pumping head ranging from 10.8 m to 17.025 m.
In these five pumping stations, which are the largest in India,
total 26 Concrete Volute Pumps each having -
Capacity- 20 m³ /second and
22 Vertical Turbine Pumps of 5 m³ /second capacity each.
A single Concrete Volute Pump of 20 m³ /second capacity can serve the daily water requirement of Burj Dubai in just 48 seconds!
The Canal Syphon built across river Banas is supported over raft foundation.
Deciding the exact location of this structure and its length was indeed challenging because of undefined river gorge and peculiar hydrology causing flash flood in the form of sheet flow.
Extensive physical model study at Roorkee and mathematical model study by CWPRS helped in arriving at the final decision.
In future too, the Project is all set to have further unique features like SCADA based Remote Monitoring and Control System, the longest Branch Canal i.e. Kachchh Branch with 360 km length involving many technical challenges enroute while passing through difficult topography and desert area which falls in Seismic Zone V.
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