Large diameter bored piles are often used for the construction of pier foundation for bridge and viaducts underwater.
The main reasons for using this foundation technique are the intervening loads and the frequent need to bore deeper to reach soil layers with good mechanical properties.
The most commonly used technique for pile boring is with Kelly bars. Standard equipment for pile drilling can be used: with a diameter up to 4 m to reach depths of 80 m and more, they are mounted on floating pontoons or spuds driven into the seabed for better stability, depending on the head of water. When working in deep water, a possible alternative to the use of pontoons is to use the same pile cap (to be constructed once piles ahve been completed) as work platform for the construction of the piers.
When working in shallow waters, a possible alternative to the use of pontoons is to realize a temporary jetty to work on with the drilling equipment.
The need to work from pontoons or temporary piers enforces strict safety regulations. Trevi has a long experience in this field, having successfully completed large and complex projects in the world.