Written by Shawn Downey on March 03, 2021
There are several solutions engineers and contractors can choose from when a deep foundation is required. With a deep foundation the structure’s load is transmitted to soils that are deeper in the ground. A deep foundation is used when a shallow foundation is not possible, not practical, or will not carry the load. Examples are weak, unstable, or expansive surface soils. Two popular options for deep foundations are helical piles and drilled shafts, also known as drilled piers or caissons.
A helical pile is a displacement foundation. Helical piles are screwed into the ground with minimal soil disturbance until the helix plates are located into stable load-bearing soil. A helical pile develops capacity through end bearing on the helical plates with little capacity developed through skin friction on the shaft. Load-bearing soil may include stiff clays, firm sands, and residual soils above bedrock.
A drilled shaft is a replacement foundation, meaning that soil is removed and replaced with a more structural material. A hole is drilled or augured into the ground and the soil is replaced with concrete. The pile can have either a straight shaft or be belled at the end. A straight drilled shaft can develop capacity in friction on the side of the shaft or on the end of the shaft in end bearing, or both. A belled shaft develops capacity primarily on the belled end in end bearing. The length of the drilled shaft is based on the strength of the soils.
While these methods may appear similar at a glance, there are some key areas in which they differ.
CHANCE pioneered the helical technology industry resulting in helical piles and anchors being used successfully around the world for a wide variety of civil construction applications, including: remedial repair of existing distressed foundations, new construction foundation for buildings, boardwalks, solar farms, anchors for tiebacks, soil nails, utility and telecommunication guy anchors.
Helical piles provide a cost-effective alternative to traditional deep foundations such as drilled shafts. If you have any questions regarding helical piles or CHANCE products, leave your comment below and we will contact you.
If you really want to dive in deep, check out the CHANCE Technical Design Manual, 4th edition.
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