The Benefits of Helical Screw Piles for Marine Construction
Helical screw piles (anchors) are steel screw-in pilings and a type of ground anchoring system used for building deep and stable foundations. They are commonly manufactured using a variety of sizes of tubular hollow steel sections for the actual pile or anchors’ shaft.
This shaft transfers a structure’s load onto the pile. Helical steel plates are welded directly to the pile shaft in accordance with the calculated ground conditions. These helixes (or helices) can be press-formed to a specified pitch or simply consist of flat plates welded at a specified angle in relation to the pile’s shaft. The number of helixes, their thickness and their position on the pile shaft as well as the shaft diameters are all determined by a combination of following:
• The combined structure design load requirement
• The geotechnical parameters
• Environmental corrosion parameters
• The minimum design life of the structure being supported or restrained.
The individual helical screw pile steel shaft sections are each subject to design parameters and building codes standards for the region of manufacture and usage.
The screw piles are literally “screwed” into the ground much like a screw into wood and are installed using various heavy construction/earthmoving equipment (a skid loader, excavator or some other suitable machinery) that has been specially fitted with rotary hydraulic attachments. This equipment is also fitted with special drive attachments, which may include rotary drives, rotary drivers and powerheads or drive heads. Correct installation techniques are essential to meeting engineered design load with consideration of the physical characteristics and settlement outcomes of the soil substrate. Incorrect installation techniques generally result in poor overall pile performance.
The level of torque that is required to turn the screw pile is indicative of the strength of the soil substrate and can be used to predict the capacity of the pile. Various devices and other relatively accurate measuring systems have been created to estimate the installation torque of a screw pile.
Helical screw pile foundations are widely used, and their usage has extended to numerous industry applications where fast installation is required, or building/rebuilding work takes place close to other existing structures.
A growing number of industries are now using helical screw pile foundations due to the cost efficiencies and the reduced environmental impact. By “screwing” the foundations into the ground there is less soil displacement so excess soil does not need to be transported away from the site which saves on transportation costs plus it reduces the overall carbon footprint of the project.
In summary, the primary benefits of helical screw pile foundations include:
• Shorter project times
• Ease of installation
• Ease of access
• Reduction of the carbon footprint
• Ease of removal when the foundations are no longer required
• Reduced risk to the workforce
• Reduced costs
A perfect example of helical screw pile application and installation:
Due to limitations of space and the need for deep foundations, helical screw piles were used to rebuild after hurricane Sandy (aka, superstorm Sandy) devastated the northeast in October 2012. Helical screw piles were the most logical solution to rebuild due to limitations of space and the need for deep foundations.
During the hosting of a Storm Recovery Resource Fair held in Nassau County, NY on January 15, 2014 at the Freeport High School in Freeport, NY it was announced that Chesterfield Associates are the only specified helical screw pile specialists on the NY Rising Approved Contractor list. Certified CHANCE Installer and NY Rising Approved Contractor, Chesterfield Associates, was in attendance with information on everything concerning helical screw pile.
With offices in New York (Long Island) and New England (Maine), Chesterfield Associates has provided many clients with efficient, cost-effective solutions for helical piling projects. These solutions have allowed for quicker installations free of any vibration concerns.