The Ductile Iron Pile System: A Cost-Effective Alternative to Traditional Micropiles
What challenges are you facing on your project?
- Working close to existing structures
- Constrained site
- Concerned about pile vibrations from driving
These are common reasons why project teams have specified drilled micropiles for foundation support. Drilled micropiles may be unavoidable at some sites, however many projects can benefit from a rapid, cost-effective alternative – Ductile Iron Piles. Experience has shown the Ductile Iron Pile alternative to drilled micropiles often cuts the foundation cost and installation time in half or more.
The Ductile Iron Pile (DIP) system
The Ductile Iron Pile (DIP) system, designed and installed by a network of regional specialty contractors throughout the United States and Canada, is a unique hybrid technology offering advantages of both driven piles and drilled micropiles. The system is installed using an excavator-mounted, medium-sized percussion hammer to rapidly advance the pile using high-frequency percussive energy. The high frequency drive energy produces minimal vibrations, allowing the system to effectively work immediately adjacent to existing buildings. Field monitoring data shows vibration levels (PPV) at a distance of only 2 feet are below 0.5 in/second. Ductile Iron Piles often provide capacities up to 100 tons in compression through end-bearing or a frictional bond zone like micropiles. Tension resistance up to 60 tons or more is also common with the friction bond zone.
Read the John D O’Bryant School case study to learn more about why the Ductile Iron Pile system was selected over drilled micropiles.
| CATEGORY | DUCTILE IRON PILES | DRILLED MICROPILES |
| Cost | $$ | $$$$
|
| Installation Rates | 400 to >1,200 ft/crew day | 100 to 300 ft/crew day
|
| Working Capacities | 10 – 100 tons | 10 – >250 tons
|
| Vibrations (PPV) | 0.3 – 0.5+ in/sec | <0.3 in/sec
|
| Load transfer mechanism | Frictional or end-bearing | Frictional
|
| Clearance (Headroom) | 15 – 20+ ft | 8+ ft
|
| Site Working Conditions | Displacement, no spoils, clean, no flushing | Drilled, spoils generated, flushing creates wet/grouted site |
The modular nature of the piles and medium-sized installation equipment allows the system to gain access to tight sites. In addition, the unique Plug and Drive connection system results in rapid installations with production rates of 400 to more than 1,200 linear feet per crew day. Unlike micropile installations, driven Ductile Iron Piles are a completely displacement process and do not require flushing of cuttings. Ductile Iron Pile sites are therefore relatively clean and created limited mess from water or grout use.
Overall, Ductile Iron Piles represent a highly-effective method to reduce installation time and cost when considering many traditional micropile applications.
