Engineering consultancy services for echo metric tests, underwater inspection and assessment of pilings of the Third Mainland Bridge in Lagos - Nigeria

The Third Mainland Bridge is a 3 lanes independent dual carriageway structure with a median separator. The overall width of the superstructure is 33.10 m. The typical spans are 45.0m in length and, in the navigable channel, 60.0m in length. Each pier consists of two slender concrete septa. The typical foundation consists of four 1.5m large diameter bored piles, with average depth of 42.0 m.

The object of the consultancy services has been the assessment of the substructure condition with particular attention to the state of preservation of the submerged parts.
To this purpose, an echo metric test campaign has been undertaken with the collaboration of Mr. Brignola of MOST Srl, an Italian expert having the CICPND Level 3 certification, according to EN 473.
Furthermore, an underwater visual inspection has been carried out with the collaboration of Messr. HydroDive Nigeria Ltd, a Company Member of the International Marine Contractors Association (IMCA).

In the first phase, the investigation has been carried out on selected foundation pilings.
A report of findings, including the results of the technical inspection on piers and pile caps, and the proposal for different types of intervention according to the severity of the damage have been issued.

Report of findings and intervention proposal (2012) for Borini Prono & Co (Nig) Ltd – Federal Ministry of Works (F.M.W.) - Nigeria.

In the second phase, comprehensive investigations and design of intervention have been carried out according to the following scopes of works:
  • Bathymetric survey of the lagoon bed along Third Mainland Bridge from Lagos to Ebute Metta, for a width of 50m upstream and 50m downstream the bridge, with a particular attention to the evaluation of erosion;
  • Execution of sonic echo tests on all the piles in water of section I and II and 25% of the piles on land;
  • Execution of coring on selected piles, where anomalies of sonic echo tests are registered; collection of samples from each core and execution of compressive tests;
  • Report of findings and conclusions of the pile testing;
  • Technical inspection of pile caps including sample Non Destructive Testing of materials, sample coring of concrete and execution of compressive tests;
  • Report of findings and conclusions of pile caps assessment;
  • Underwater inspection and collection of pictures and videos of all the piles of the section I (from Lagos to Ebute Metta) and of the 50% of the piles of the section II (from Ebute Metta to Oworonshoki) of Third Mainland Bridge;
  • Report of findings and conclusions, including the results of the underwater inspection as well as the comparison with the results of echo metric tests and tests on concrete;
  • Identification and description of the most appropriate rehabilitation intervention for every type of damage detected on piles and recommendations for the rehabilitation;
  • Preparation of BEME;
  • Preparation of tender documents.
Assignment for the Federal Ministry of Works (F.M.W.) in 2013.