UK TESTING contractor Testconsult is supplying equipment, personnel and technical support for the assessment of bridge foundations on the Bandra-Worli Sea Link project in Mumbai, India.
The project, part of the Western Freeway scheme, comprises 5.6km of road, including a 600m long cable stayed bridge across Mahim Bay in the congested western suburbs of the city.
Main contractor is the locally-based Hindustan Construction Company (HCC), working for the Maharashtra State Roads Development Corporation (MSRDC). US firm Amec Earth & Environmental is consultant on site assessing testing work.
The foundations of the main 158m high tower will be 2m diameter drilled shafts with an estimated length of 30m.A cofferdam and tremie seal construction is planned to allow bases to be built in the dry. The tower will incorporate a viewing platform, accessed by a capsule elevator from a dock at its base.
Piles for the approach piers are 1.5m diameter and HCC is installing offshore piles from bargemounted cranes.
Piles incorporate sonic logging tubes to enable the integrity of concrete shafts to be assessed ultrasonically before construction of pile caps and piers.
Four metal access tubes are fixed to the inside of the reinforcement cage over the full pile length, enabling up to six profiles to be taken for each pile.
Off-shore trial piles have been installed with Osterberg cells at the base and at mid-depth to carry out static load tests.
Testconsult has supplied HCC with a CS97 sonic logging system, and is carrying out a programme of testing trial piles and working piles both on- and offshore. The firm is also providing technical support and training to HCC's staff and to MSRDC, to give a better understanding of sonic logging test theory and interpretation of results.
Testconsult managing director Huw Williams said the advantage of sonic logging were that piles could be tested even though they were tied into the structure, and to any depth without signal loss.
'The exact depth of any anomalies can be identified, as well as the horizontal extent and severity, ' he said. 'Sonic logging is now the preferred method of assessing the integrity of large diameter piles on most major international projects.'
Recent projects include the Trans-Taiwan Rail Link and the Bahraib Road Bridge Project in Bangladesh.
The technique is also being used extensively in the UK on the Channel Tunnel Rail Link and at various sites at Canary Wharf in London Docklands.
'Its popularity is largely due to the relative ease of interpretation and accurate identification of anomalies, 'Williams said.