We’ve reported regularly about exciting new foundation methods in Shanghai. On my last site visit I witnessed the longest steel foundation piles ever driven by vibratory hammer in Shanghai. At Yanjiang Corridor the 700mm casings had a length of 73.5 meters. Each pile consists of 4 sections. The STEC Road & Bridge team do their job well. Special care is taken to position the hammer straight on the pile in order not to deform the rim of the casing so that welding of each section is seamless. Matching the concavity of the jaw plates to the casing diameter will ensure a perfect grip on the pile and minimal shape deformation. Jaw plates can be ordered according to each specific need.

STEC has invested in dedicated hoisting equipment, the 28RF is operated from a piling rig with a 30-meter-high mast to get good verticality on the pile, the 70RF is lifted by a 150T crane that allows for a good reach. Because the crane is dedicated to the hammer, the crane’s counter weight has been switched out for the power pack. This has several benefits, hoses don't get dragged over the ground, and the piling hammer and power pack don't have to be moved frequently as they just ride along with the crane.

The photo’s that accompany this article show an incredibly tidy working environment. As permanent steel casing foundations require no bentonite, displace no soil, and have require a bare minimum of raw concrete there is not much mess to be made. After the foundation has been made, prefabricated road elements arrive on site and are installed much like a model kit.

So why did the SMI chose steel casings driven with RF hammer for this project? Invisible to the naked eye of the passerby there are in fact gas lines running below the road surface…. following the white line underneath the asphalt. The RF and steel pile combination ensure both that no lines are affected by resonance vibrations, and secondly no soil around the pipes is displaced. 

At first sight steel foundations are seen as outrageously expensive, but the enthusiastic adaptation of this method in Shanghai shows that the benefits far outweigh the perceived price tag. The main benefits are very high construction speeds, and low impact to the environment.

Future foundation designs Shanghai  are trending to larger pile diameters. At locations where construction work requires traffic closure during pile driving, a massive 4 or 5-meter diameter pile could take the function of many smaller piles. Currently the 70RF is largest hammer available in the market, preparations are now ongoing to use multiple hammers in what is known as a tandem configuration. 

Tandem configurations are already common in offshore applications, NTOC uses a 200NF tandem for offshore pile positioning, and China Railway Major Bridge Corporation has invested in a tandem 170NF to tackle the driving and extracting of larger diameter and heavier piles for bridge projects.

Contact us today for further reading material, or to make an appointment with one of our technical advisors to see if this working method is viable in your city.