Ductile Iron Piles are an innovative deep foundation solution that can address a wide-range of geotechnical and construction challenges. With installations to treat a variety of soil conditions including fill, organics, soft clay and loose sand, Ductile Iron Piles can develop high capacities in either end-bearing or by developing a grouted bond zone to transfer loads in friction. The system is installed with medium-sized excavators for easy mobilization to a project site. The modular 5-meter long pile sections are easy to transport and move around tight sites. Installation using high frequency percussion hammers results in low vibrations, allowing the system to be used in close proximity to structures. With rapid installation rates of 600 to greater than 1,400 LF per day, Ductile Iron Piles are often faster and more economical than traditional deep foundations including micropiles, helical piles, driven H-piles, or pipe piles and augercast piles.
Ductile Iron Piles can address a variety of geotechnical construction challenges.
Installation Process: End-Bearing Ductile Iron Piles
- A flat or pointed driving shoe is inserted over the end of the hollow pile.
- Using a hydraulic hammer (high-frequency impact energy) the pile is driven into the ground.
- Driving continues until the Plug & Drive socket end approaches working grade. The time required to drive each meter increment (driving resistance) is observed throughout the entire driving process.
- The second Ductile Iron Pile’s spigot end is then inserted into the socket end of the existing pile.
- Steps 1 to 4 are repeated until the pile reaches the pre-determined driving criteria or terminates on refusal.
*If interior grout is used, the grout can be added after multiple piles have been installed or after the first pile achieves the required depth.
Installation Process: Friction Ductile Iron Piles
- A patented oversized conical end cap is inserted over the end of the pile.
- The hydraulic hammer, accompanied by a grout driving shank which allows for the simultaneous pumping of grout, drives the pile into the ground.
- The interior of the pile is filled with grout and travels out through the conical end cap. Grout fills the annular space created by the oversized cap and returns to the surface. The adjacent soil is improved during the driving process, creating the grout/soil interface to provide efficient skin friction along the friction pile.
- Driving continues and the grout is continuously pumped until the Plug & Drive socket approaches working grade.
- The time required to drive each meter increment is observed throughout the entire driving process.
- The spigot end of the second pile is then inserted into the existing pile.
- The driving/grouting process is repeated until the pile reaches the sufficient design depth in the terminating layer.
How the Technology Works
Ductile Iron Piles are manufactured using a centrifugal casting process to create the unique bell-spigot section. The casting process results in a lamineer ductile cast iron that exhibits superior resistance to the high frequency impact stresses during driving. The pile is advanced with low vibration levels due to the high frequency nature of the percussion hammer. This energy dissipates rapidly with distance from the pile installation, allowing for the system to be used immediately adjacent to structures. The pile material exhibits strengths comparable to steel (46 ksi) to deliver moderate to high structural capacity. Further, the bell-spigot connection is specifically designed to develop strength through a compression fit that generates strength through hoop stress and also from cold (friction) weld that joins the spigot-bell sections during driving.
The piles are engineered for use with a variety of soil conditions and project types. The system develops capacities ranging from 25 tons to greater than 100 tons. End-bearing piles are designed to transfer foundation loads to either rock or a dense strata (i.e. glacial till). Piles have been driven up to depths of 175 feet to develop resistance in end bearing on rock. The system is also used in conditions where the piles can penetrate a problematic soil condition and transfer loads in friction to a more competent underlying soil strata. For example, friction Ductile Iron Piles are often used in New England to transfer loads through fill and organics to underlying medium dense sand. Ductile Iron Piles are then installed with an oversized conical grout shoe and grouted during driving to create a frictional bond zone in the sand layer to generate capacities and transfer foundation loads in friction. In the event that tension resistance is required, a high strength center reinforcing bar is inserted into the center of the grouted pile. The high strength bar is then structurally tied to the pile cap. The frictional capacity in these conditions is able to provide compression as well as tension resistance by engaging the length of the friction bond zone.
Following pile installation, the piles are cut and capped with a bearing plate. The piles are then encapsulated in concrete during the pile cap construction.
Ductile Iron Piles are often used as an alternative to drilled micropiles, driven H-piles or steel pipe piles, helical piles and augercast piles to save foundation costs and accelerate project schedules.
Advantages of Ductile Iron Piles
- Cost-effective, providing a 15-25% cost savings over drilled micropiles and driven piles
- Rapid installation calls for shorter schedules as daily production rates range from 600 to 1,400 feet
- Moderate to high load-carrying capacity
- Minimal material waste
- Low vibrations are optimal for installation to occur at urban, constrained sites
- Modular pile sections allow for rapid work in constrained and limited lay-down areas
- Recycled content to support green construction and LEED ratings
- Limited to no spoils to provide clean work site and reduce environmental compliance issues on contaminated sites.
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