Chances are, you’ve never heard of Alexander Mitchell. Perhaps that’s because he was born in 1780 and lived primarily in Ireland. However, he’s responsible for inventing the helical pier.
If you’re not familiar with helical piers, also referred to as helical or screw piles, here’s a basic definition: deep foundation solutions utilized to secure new foundations or repair existing ones. They’re screwed into the soil, similar to a corkscrew. Plus, they are popular due to their ease of installation and low soil disturbance.
Mitchell, who became blind in 1802, created the helical pier in the 1830s to stabilize structures constructed on sand, mud and similar bases. It was first used to build and support the Maplin Sands Lighthouse, located by the Thames River in England. Traditional foundation methods didn’t work well because of the soft mud at the bottom of the river.
The first helical piers were made of cast or wrought iron, but their capacity for bearing and tension was limited. After its initial development, helical pier technology was used to build bridges, more lighthouses in tidal basins around England and other structures. The invention was then patented by Mitchell and his son.
The use of helical piers in the United States began in 1838 with the construction of Brandywine Shoal lighthouse in Delaware Bay. After the Civil War, they were used increasingly to build other lighthouses. This is primarily because of a decision by the Lighthouse Board. Basically, it was a U.S. government agency responsible between 1852 and 1910 for the construction and maintenance of all lighthouses in the country. The agency chose to replace lighthouse vessels serving in interior waterways with helical pier lighthouses. Because of this decision, more than 100 lighthouses were constructed using helical pier technology to replace older structures.
Along with Delaware Bay, many helical pier lighthouses were built in Chesapeake Bay, including the Hooper Strait Lighthouse. In fact, there were 42 lighthouses erected on Chesapeake Bay from 1850-1900. Others were constructed off the coasts of Maryland, Florida and other eastern states and near the Gulf of Mexico. The Carysfort Reef Light lighthouse, which is located about six nautical miles east of Key Largo, Florida, is the oldest helical pier lighthouse that remains in service in the U.S.
In the 1950s, helical piers were utilized by the electrical power industry for towers, pipelines and utility poles. The difference was that power-driven helical screw anchors were added for the purpose of resisting tension loads.
Made of galvanized steel, helical piers used now come in multiple sizes, can hold approximately 500 tons and are used in residential, commercial and industrial applications across the globe. Compared to other common foundations, they are:
At PierTech, we manufacture a full line of helical pile products and installation equipment and are a leading producer of helical piles, piers, connection accessories and foundation repair equipment. Our patented products, which are made here in the U.S., are built using the highest tensile strength and yield strength domestic steel on the market.
We offer two patented types of piers: round shaft, which is best used in compression situations, and square shaft, designed for tension situations. Our line of helical piering equipment is the only equipment on the market designed and manufactured specifically for the screw pile industry. This includes helical piers and anchors ranging from 1-1/2” square shaft to 16″ round shaft and drive heads from 5,000-375,000 foot pounds of torque.
Read about some of the projects we’ve completed for our customers, and contact us to see how we can benefit your project, no matter the size.