HELICAL PILES

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HELICAL PILE DESIGN

Helical piles, also known as screw piles, are steel shafts with helical flights welded at strategic positions along the shaft. The size of the helical flights varies depending on the ground conditions of the site and the load the helical piles will anchor. The helical flights give the foundation both tension and compression bearing capacity which enables them to be used for a wide range of applications.

At Helical Pile Solutions, we design our helical piles to suit specific site and ground conditions. The correct size and configuration of helical piles depends on multiple factors which is why we do not advertise helical pile capacities on our website. Only once we have specific site and project information can we give you an accurate estimation of the number of piles you will need, their size and their configuration.

HELICAL PILE INSTALLATION PROCESS

Helical piles are screwed directly into the soil, anchoring the weight of their load to the surrounding ground. Load capacity and pile length is predetermined before beginning the installation in order for the installation operatives to monitor the results as the pile is advanced to its final datum level.             

During the installation process, the helical piles are installed using standard tracked or wheeled excavators with a torque drive motor attachment and Intelli-Tork device which monitors the torque achieved during installation. The device also provides full transparency of data inclusive of date, time, GPS location, depth, rotations and angle to capture all the data required to adhere to BS8004:2015 specification that all Helical Piling contractors must comply with.

The helical piles are advanced to a predetermined design bearing strata by rotating the steel shafts with the torque motor that is attached to the excavator. Multiple steel sections are connected via a bolted connection and sections are added to complete the total pile depth which is determined by the size, shape and build of the load it will support.

Helical flights welded at strategic positions along the shaft are designed to penetrate the soil without augering (True Helix) whilst the torque is carefully monitored as the pile advances. As the helical piles are advanced, a final torque reading is taken over the last 1m of advancement to ensure the pile is achieving the required design before terminating at the correct datum level.

Due to their helical nature, helical piles are able to withstand a range of axial, uplift and shear forces. By increasing the diameter of a pile, wall thickness, the size of the helix plate, and quantity of helix on each pile, larger loads can be anchored. The exact size and configuration of the helical piles varies from project to project, depending on multiple factors including site conditions and load.

Once the helical pile has been advanced to the correct datum level, the top of the pile can be connected to the structure in multiple ways, either by a direct steel flange plate connection or plate/rebar connection to concrete.

ON-SITE PLANT

To advance helical piles into the ground, Helical Pile Solutions uses a range of excavators, the size of which depends on various factors. Excavators vary in size from as small as 5-tonnes up to 50-tonnes however the typical size machine we use on most projects would be either a 13-tonne or 21-tonne tracked excavator.

Excavators are predominantly steel tracked machines, however where we want to ensure that the existing ground remains undamaged we would opt to use a rubber tracked or wheeled excavator.

To install helical piles using an excavator, we remove the bucket and replace it with a torque drive unit which enables the rotation of the piles using the hydraulics from the parent machine. Each torque drive unit is paired with the parent machine in accordance with the correct flows, pressures and lifting capacities.

Where site access is tight and large machines cannot gain access, we also offer a range of lightweight torque drives that can be fitted onto very small excavators or managed by hand (handheld) making tight access projects achievable.

HISTORY OF HELICAL PILES

While modern helical pile technology was introduced to the UK in 2000, the first helical pile was, in fact, invented here in the 19th Century.

In 1833 the first helical style piles were invented by Alexander Mitchell, a blind Irish builder and brick manufacturer. His invention met a need for effectively mooring ships and tankers to England’s silty river bottoms. Quickly realising the potential of his invention, he patented the design and began promoting it for structural use. It was first used for compression to support the Maplin Sands Lighthouse in the Thames River in 1838 – a lighthouse that still stands today.

The technology was also welcomed in the United States and Gulf of Mexico where helical piles were used as the foundations for more than 100 lighthouses over the following 50 years.

In North America, the use of Helical Piles expanded from the marine sector to become increasingly used in other industrial applications. Today, helical pile technology is credited for the construction of many structures around the world that wouldn’t have been possible to build with any other type of foundation.

In 2000, today’s advanced helical pile technology was introduced to the UK and it has quickly become the preferred foundation choice for many structures across multiple industries. With their relative ease to install, immediate load bearing capability and minimal disruption to site and local area, their popularity continues to grow.

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