UNDERLENGTH PILES on a prestige Hong Kong Central development have prompted a major investigation and extensive remedial works, it emerged this week.
Hong Kong's Building Department is now considering whether to take action. The investigation was launched into the £55M foundation contract after more than 80 concrete piles were found to be defective.
The registered contractor Aoki only found out about the problem after an anonymous tip-off last October. It appears that piling records may have been deliberately falsified by a local piling subcontractor without the knowledge of the other contracting parties.
Ove Arup & Partners (Hong Kong) is the registered structural engineer, responsible for supervising installation of the large diameter bored piles.
Building Department chief structural engineer PL Ip said: 'Under the Hong Kong Buildings Ordinance and Regulations, it is the statutory duty of the registered contractor to provide continuous supervision and the registered structural engineer to provide periodic supervision on building works for which they are responsible.'
Investigation into the problem was carried out jointly by the Buildings Department and Ove Arup (HK) after the piling was complete. Ip said his department was considering 'any necessary follow up action under the Buildings Ordinance'.
The Buildings Department has the power to prosecute if serious irregularities are found.
The piles are designed to support a shopping centre forming part of the Phase 2 development of the new Hong Kong Mass Transit Railway station. Defective piling is believed to be valued at £9M. Diameters range from 1.5m to 2.5m, and each should have been keyed into the granite bedrock at depths of 30m-70m to resist uplift forces.
Sources close to the project confirmed on Tuesday that the defective piles had been installed without the specified 5m key into the rock.
The piles were installed by the local piling subcontractor - since understood to have ceased trading. Under a complex contractual arrangement, the work had been sub-let first to Bachy Soletanche, who had in turn then let the piling to German contractor Bilfinger & Berger. The package was then finally subcontracted to the local firm now under suspicion.
Full details of the debacle have been kept confidential since problems were first discovered last October, while the Buildings Department considers what action to take.
Ip commented: 'Normally I would expect something like this to be picked up.' He added that the department was 'naturally concerned' that the same thing could happen on other sites and would take 'appropriate action' if it found any contravention of the regulations.
Ove Arup (HK) structural engineering director John MacArthur refused to comment on checking procedures on the contract. But he said: 'The remedial works and repairs were all approved by the government and should be finished in the next two weeks. We have found ways of changing the excavation sequence and the following-on works and hope to mitigate the delays.'
Both Aoki and Bilfinger & Berger were unavailable for official comment.
Remedial works to allow the scheme to continue started in February. They are being carried out by the remaining contractors and are understood to have taken two basic approaches. The larger diameter piles have been extended by driving steel H-section piles through shafts bored through their centres. Smaller diameter piles have had to be corrected by installing new concrete piles adjacent to them.
The piling work is part of a large foundations contract for property development consortium Central Waterfront Properties, which will carry out the Phase 2 development of the Hong Kong MTR station. The contract will include foundations for the planned 420m North East Tower - set to become the world's fifth tallest building.
Phase 1 of the five storey deep MTR Hong Kong station will link the island to the new Hong Kong International Airport, and is due for completion later this month.