This paper presents the geological conditions and the geotechnical properties developed through field and laboratory testing for the design and construction of the Bandra-Worli Sea Link (BWSL) project (now dedicated as the Rajiv Gandhi Sea Link) in Mumbai, India. The BWSL which opened in July 2009, included a 500 m long cable stayed bridge with two 250 m cable supported main spans on either side of a single central tower with a height of 128 m. The structure spans the mouth of Mahim Bay adjacent to the Arabian Sea. As a contract requirement, additional borings at selected locations along the alignment and at each pier location were taken by the contractor. Rock samples at various depths from the borings were tested in the laboratory to further classify the material and to estimate engineering properties. Four Osterberg load cells tests were performed to assess ground behavior, verify that the design loads did not exceed the design capacity, validate the design approach, and evaluate construction methods and thereby increase the reliability and efficiency of production drilled shaft construction operations. The additional borings exposed extensive geologic variability across the site that was not apparent from the preliminary site investigation resulting in the requirement that each pier location be treated independently to establish site specific tip elevations for the drilled shafts.
This paper presents the geological conditions encountered and the geotechnical properties developed through field and laboratory testing for the design and construction of the Bandra-Worli Sea Link (BWSL) project (now dedicated as the Rajiv Gandhi Sea Link) in Mumbai, India. The BWSL which opened in July 2009, included a 500 m long cable stayed bridge with two 250 m cable supported main spans on either side of a single central tower with a height of 128 m. The structure spans the mouth of Mahim Bay adjacent to the Arabian Sea. Preliminary design of the foundation elements was based on widely spaced borings and a limited geophysical investigation. As a contract requirement, the owner, the Maharashtra State Road Development Corporation Ltd. (MSRDC) which was appointed responsibility for the project by the Government of Maharashtra, India, specified additional borings at selected locations along the alignment and at each pier location be taken by the contractor. The additional borings exposed an extensive geologic variability across the site that was not apparent from the preliminary site investigation resulting in the requirement that each pier location be treated independently to establish site specific tip elevations for the group of drilled shafts within the pile caps. Rock types consisted of basalts, volcanic tuffs and breccias and some intertrappean deposits. These weathered rock beds in some places are overlain by transported soils, calcareous sandstone, and by thin beds of coarse grained conglomerate. The top of these strata are covered by soft silty clay in places. The strength of these different rock types ranged from extremely weak to extremely strong and at conditions ranging from highly weathered and fractured to fresh, massive and intact.
