The Bandra-Worli Sea Link (BWSL) is a civil engineering marvel spanning an arc of the Mumbai coastline. With its cable-stayed towers soaring gracefully skywards, the sea link is a reflection of the modern infrastructure that Mumbai is adding in its progress towards becoming a world-class city. The BWSL project is a part of the Western Freeway Sea Project.
The Bandra-Worli Sea Link is primarily meant to provide an alternative to the Mahim Causeway route that is presently the only connection between South Mumbai and the Western and Central suburbs. The project has been commissioned by the Maharashtra State Road Development Corporation Ltd (MSRDC) and the Maharashtra Government and is being built by HCC (Hindustan Construction Company).
| Design | Cable-stayed main spans; concrete-steel precast segment viaducts at either end |
|---|---|
| Total length | 5.6 kilometres (3.5 mi) |
| Width | 2 x 20 metres (66 ft) |
| Height | 126 metres (413 ft) |
| Longest span | 2 x 250 metres (820 ft) |
| Designer | Seshadri Srinivasan |
| Constructed by | Hindustan Construction Company, India |
| Construction begin | 2000 |
| Construction end | 24 March 2010 |
| Opened | 30 June 2009 |
Surveys of the seabed under the planned route were conducted before the bridge design commenced. The marine geology underneath the bridge consists of basalts, volcanic tuffs and breccias with some intertrappean deposits. These are overlain by completely weathered rocks and residual soil. The strength of these rocks range from extremely weak to extremely strong and their conditions range from highly weathered and fractured, to fresh, massive and intact.
Highlights in brief
• India’s first bridge to be constructed in open-sea conditions
• 4.7 km, twin, 4-lane independent carriageway bridge across the open sea
• 16-lane toll plaza with 20-m wide promenade together with state-of-the-art traffic monitoring, surveillance, information and control systems
• 2342 pre-cast segments for total bridge with varied width
• 40,000 MT of reinforcement, 23,0000 cum of concrete, 5,400 MT of Post tensioning strands and bars used
• Up to 25-m high pier in open sea, giving ample headroom to marine traffic
• Use of Polytron Disc in bearings on piers for the first time in India.
Project overview
Package I: Construction of flyover over Love Grove junction at Worli
Package II: Construction of cloverleaf interchange at Mahim intersection
Package III:Construction of solid approach road from the Mahim intersection up to the start of the Toll Plaza on the Bandra side and a public promenade
Package IV: Construction of Cable-Stayed Bridges together with viaduct approaches extending from Worli up to the Toll Plaza at Bandra end, Intelligent Bridge System (IBS).
Package V: Improvement to Khan Abdul Gaffar Khan Road Package IV is the largest and main phase of Bandra-Worli Sea Link Project.
Main features of this technically challenging package are:
• Cable-Stayed Bridge including viaduct approaches extending from Worli up to Toll Plaza at Bandra end
• Modern Toll Plaza The work under this package was awarded to HCC.
Challenges encountered during execution of the project Engineering challenges BWSL Project is a unique and pleasing structure, but before undertaking the construction, following were the major challenges to be addressed:-
• The foundations of the bridge included 604 large diameter shafts drilled to lengths of 6m to 34m in geotechnical conditions that varied from highly weathered volcanic material to massive high strength rocks.
• The superstructure of the approach bridges were the heaviest spans in the country to be built with span-by-span method using overhead gantry through a series of vertical and horizontal curves.
• A one-of-its-kind, diamond shaped 128m high concrete tower with flaring lower legs, converging upper legs, unified tower head housing the stays and a throughout varying cross section along the height of tower.
• Erection of 20000 MT Bandra cable-stayed deck supported on stay cables within a very close tolerance of deviations in plan and elevation.
The challenges were varied and started right from the Pre-Cast yard.
The working load on the approach piles ranges from 700 tons to 1500 tons whereas for the piles below the cable-stayed bridge working load is 2500 tons.
Cable Stay bridges It is for the first time that cable stay bridges have been attempted on open seas in India.
PYLON TOWERS
The largest pylons for the bridge consist of diamond shaped 128 metres (420 ft) high concrete tower featuring flaring lower legs, converging upper legs, a unified tower head housing the stays and a continuously varying cross section along the height of tower.
The bridge’s pylon towers gradually decrease in cross-section with height. They have horizontal grooves every 3m in height, which permitted inserts. Vertical grooves in the circular sections require special form liners, as well as require attention for de-shuttering. The tower legs are inclined in two directions, which presented challenges in alignment and climbing of soldiers. Construction joints were permitted at 3m intervals only.
Structure
BWSL consists of twin continuous concrete box girder bridge sections for traffic in each direction. Each bridge section, except at the cable-stayed portion, is supported on piers typically spaced 50 metres (160 ft) apart. Each section is designed to support four lanes of traffic with break-down lanes and concrete barriers. Sections also provide for service side-walks on one side. The bridge alignment is defined with vertical and horizontal curves.
The bridge consists of three distinct parts: the north end viaduct, the central cable-stayed spans and the south end viaduct. Both the viaducts used precast segmental construction. The cable-stayed bridge on the Bandra channel has a 50m-250m-250m-50m span arrangement and on the Worli channel it has a 50m-50m-150m-50m-50m span arrangement.
Panorama view of Bandra Worli Sea Link
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