A hollow round timber piling system will be tested at 840 Colombo Street on August 23 and interested parties have been invited to watch. Bring a hard hat and high viz jacket if you have them.
The test at 4pm will interest those looking at rebuilding on soft ground, particularly in areas that have been affected by liquefaction due to lateral spread. The land on the former Mainland restaurant site is soft to about 13 metres and should provide a good test of the timber system.
The system has been developed by MLB consulting and TTT Products Ltd and will offer a cheaper alternative to traditional concrete piles. Cost estimates indicate that 18m timber piles are approximately 40 per cent of the cost of bored concrete piles.
The system has been successfully tested in granular subsoil using a vibrating driving head and water jetting through the centre of the pile to reduce driving resistance. If necessary the pile tip can be grouted, solidifying any disturbed material.
However, there are some potential issues with driving piles through alluvial silts, sands and gravels. There are high levels of ground vibration plus the potential for pile damage as a result of resistance.
The technical information draws heavily on this newsletter from mlb consulting engineers