CHANCE® Helical Pile Technology: Structural Elevation Product Solutions
Building elevation plans can vary depending on geotechnical properties of the soil, the design of the supported structure and the building codes. Regulations and current engineering interpretations in each geographical location are also a concern. The primary solution for building elevation recommended by Hubbell Power Systems, Inc. is the CHANCE Helical Pulldown® micropile (HPM). Based on the same methodology as standard CHANCE helical piles, the HPM has several undisputable benefits that provide excellent stability in structural elevation. For added assurance, the HPM is backed by an industry leading 30-Year Limited Transferable Product Warranty.
- Flood zone building requirements
- Design approach for CHANCE helical pile technology
- What is a CHANCE helical pile?
- What is a CHANCE Helical Pulldown micropile?
Flood Zone Building Requirements
When lifting a structure within a flood zone, the rules and regulations can vary depending on location, soil type, structure size, and more. FEMA elevation requirements are constantly changing, but one thing that remains consistent across all locations is that CHANCE Helical Pulldown micropiles are trusted for any project.
FEMA Flood Zone Recommendations:
- Helical piles can be designed for ALL ZONES
- A-Zone: cross bracing is recommended
- V-Zone: avoid cross bracing when possible
- Grade beams are acceptable in all zones
- For the latest flood zone home elevation requirements from FEMA, visit www.fema.gov
Structural Elevation Design Approach for CHANCE Helical Pile Technology
The recommended product for structural elevation is the HPM (cased). Design modifications or additional products can be suggested to meet or exceed needs based on specifications determined by local engineer. Contact us at 855-477-2121 for additional design assistance with your project’s specifications for properly raising a building above required elevation.
Basic process for a cased HPM:
- Extend pulldown to required height
- If required, increase the superstructure column capacity with steel, masonry, or concrete
- Lower home onto connections
Additional Engineering Design Considerations:
- Helical pile required torque
- Connection fixity to the underside of the home
- Load combinations
- Frame analysis (sway/non-sway)
- Second order analysis
- Combined bending and axial load
Design Approach for CHANCE Helical Pile Technology
Recommended product for install begins with the cased HPM and design modifications or additional product can be suggested to meet or exceed needs based on specifications determined by local engineer. Contact 855-477-2121 for additional design assistance with your project’s specifications to properly raise home above required elevation.
Basic process for a cased HPM:
- Extend the helical pulldown to required height OR If required,
- Increase the superstructure column capacity
- With steel, masonry, or concrete
- Lower home onto connections
Additional Engineering Design Considerations:
- Helical pile required torque
- No geotechnical information? Then what?
- Connection fixity to the underside of the home
- Load combinations
- Frame analysis (sway/non-sway)
- Second order analysis
- Combined bending and axial load
- Eccentricity on column connections
- Freeze thaw for grade beams
CHANCE HeliCAP® software is interactive software that helps you solve your tension and compression project requirements with helical anchors. It performs powerful calculations with your site soil parameters to help you build better and faster. To learn more, click here.
What is a CHANCE Helical Pile?
A helical pile is a deep foundation system that is primarily used to support or resist the weight (load) of a structure within virtually any application. Helical piles are installed by mobile equipment, ranging in size depending on the load requirements. The most beneficial aspect of a helical pile is that it can be loaded immediately, unlike other deep foundation methods such as concrete.
3 Essential Elements of a helical pile:
- At least one bearing plate (helix)
- A central shaft
- A termination
Helical pile sections are joined with bolted couplings, allowing the pile to be continuous and leaving the installation depth limited only by soil density and practicality based on economics. The large majority of CHANCE helix plates, regardless of their diameter, have a standard 3″ pitch. Being a true helical shape, the helix plates do not auger into the soil but rather screw into it with minimal soil disturbance. CHANCE helix plates are pre-qualified per the requirements in the ICC-ES AC358 acceptance criteria for helical pile systems and devices, meaning they are generally circular in plan, have a true helix shape, and are attached perpendicular to the central steel shaft with the leading and trailing edges parallel. Helix plates are spaced at distances far enough apart that they function independently as individual bearing elements. Consequently, the capacity of a particular helix on a helical pile/anchor shaft is not influenced by the helix above or below it.
What is a CHANCE Helical Pulldown Micropile (HPM)?
The CHANCE HPM is a patented (U.S. patent 5,707,180) method used to form a grout column around the shaft of a standard square shaft or pipe shaft helical pile/anchor. The installation process can employ grout only or grout in combination with either steel or PVC casing. The result is a helical pile with grouted shaft similar, in terms of installation, to drilled and grouted anchors or auger cast-in-place piles using gravity grouting.
The initial reason for developing the HPM was to design a helical pile with sufficient shaft size to resist buckling. However, since its inception, the method has demonstrated more advantages than simply buckling resistance. The advantages and limitations, based on the results of field tests, are summarized herein:
- Increase buckling capacity of a helical pile shaft in soft/loose overburden soils to the point that end-bearing controls failure.
- Increased compression capacity due to the mobilization of skin friction at the grout/soil interface. Total capacity is a function of both skin friction and end-bearing
- Provides additional corrosion protection to anchor shaft in aggressive soils. The grout column provides additional corrosion protection to the steel pile shaft from naturally occurring aggressive soils with high metal loss rates, organic soils such as peat or other corrosive environments like slag, ash, swamp, chemical waste, or other man-made material.
- Stiffens the load/deflection response of helical piles. Axial deflection per unit load is typically less than with un-grouted shafts.
The installation procedure for CHANCE Helical Pulldown micropiles (HPM) is rather unique in that the soil along the sides of the shaft is displaced laterally and then replaced and continuously supported by the flowable grout as the pile is installed.
To learn more about CHANCE foundation support systems visit call our customer support service line at 855-477-2121.
If you are an engineer looking for technical support, please call 855-477-2121 to connect with a Hubbell application engineer who can assist with a customized application design.