The Shanghai government ordered the building of recreational paths along the banks of Huangpu River to offer residents better access to the iconic views along this stretch of water. By the end of 2017, a total stretch of 45km of green space along the river front will be open to the public. The six pedestrian bridges that were commissioned along the east banks have now started construction. The bridges cross several estuaries that flow into the Huangpu.
 

Although the project is for unmotorized traffic it is still a challenging job. The construction area is extensive and crosses different property boundaries, there is a tight 155-day schedule for completion, and as the bridges as part of the landscape design the construction standard is higher than for regular bridges. The river bed poses a challenging and complex soil profile with varying water depth and soil deposits. Permanent steel casing foundations were chosen in order to complete the project in time, but these require highly specialized equipment that assures adjacent foundations remain undamaged.
 
The permanent steel casings that were chosen as the foundation type for the project have three diameter sizes: 700mm, 900mm, and 1200mm. The length of each foundations piles is around 50 meters. A total of 99 piles are needed for the project. Before the concept of steel foundations for elevated highways was proven with the construction of Shanghai Beiheng Corridor and Shanghai S3 highway projects, these type of foundations were typically done with concrete cast in situ piles.
 





The benefits of steel foundations are:

1. The foundation pile is directly driven into the soil, this saves a lot of construction time

2. No soil is displaced during the driving of the casing, this leaves the surrounding soil layers undisturbed

3. The method has no excavated soil, no drilling mud, and no concrete. This saves material and material handling costs.

Equipment
The piles were driven by a carefully selected mix of ICE vibratory hammers that offered a varied driving force and amplitude. Some of the shorter piles were driven with the 28RF, a medium sized RF hammer. Others were driven by normal frequency 1412C hammer, or by the world’s largest resonance free hammer: the 70RF.
 
Driving method
The client used two mobile cranes; a 150t crane to lift the hammer, and a 50t crane to hoist the piles into place. The 50m piles arrived on site in 13m long sections and were welded together on the spot during pile driving.





The 99 piles ranging in diameter from 700 to 1200mm, and with a length from 35m reaching up to 52m, were all driven to depth without fail. Permanent steel foundations have revolutionized building practices in Shanghai and have once again proven to be cost effective foundation choice.