In 1800, British engineers combined seven islands around Bombay into one. When the american civil war strangled the cotton trade, then Bombay filled the void and got range for exporting. When the Suez canal opened, Bombay became one of the greatest ports on the arabian sea.
The Bandra–Worli Sea Link, officially called Rajiv Gandhi Sea Link, is a cable-stayed bridge with pre-stressed concrete-steel viaducts on either side that links Bandra in the Western Suburbs of Mumbai with Worli in South Mumbai. The bridge is a part of the proposed Western Freeway that will link the Western Suburbs to Nariman Point in Mumbai's main business district.
Project Details - The project was commissioned by the Maharashtra State Road Development Corporation Limited (MSRDC). The foundation stone was laid in 1999 by Bal Thackeray. The original plan estimated the cost at ₹6.6 billion (US$98 million) to be completed in five years. But the project was subject to numerous public interest litigations, with the 5-year delay resulting in the cost escalating to ₹16 billion.
The overall project consisted of five parts, contracted separately to accelerate the overall schedule.
Package IV was the main phase, with the other packages providing supporting infrastructure.
Geology 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 and the strength of these rocks range from extremely weak to extremely strong.
Design BWSL was designed as the first cable-stayed bridge to be constructed in open seas in India. Due to the underlying geology, the pylons have a complex geometry and the main span over the Bandra channel is one of the longest spans of concrete deck attempted. The Bandra–Worli Sea Link was the first infrastructure project in Mumbai to use seismic arresters. These will enable it to withstand earthquakes measuring up to 7.0 on the Richter scale.
Foundation and Structure The construction of the bridge's structure presented major engineering challenges. These included the highly variable geotechnical conditions due to the underlying marine geology of the seabed. The foundations for the BWSL's cable-stayed bridges consist of 120 reinforced concrete piles of 2,000 millimetres diameter.
Pylon tower The largest pylons for the bridge consist of diamond shaped 128 metres 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.
Pre-Cast Yard The Precast yard was located on reclaimed land. The yard catered to casting, storing and handling of 2342 concrete-steel pre-cast segments for the project.
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 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 superstructure comprises twin precast concrete box girders with a fish belly cross sectional shape, identical to the approaches. A typical Precast segment length is 3.0 metres with the heaviest superstructure segment approaching 140 tonnes. Balanced cantilever construction is used for erecting the cable supported superstructure as compared to span-by-span construction for the approaches. For every second segment, cable anchorages are provided.
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.
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