![StackOfScrewPiles](https://upload.wikimedia.org/wikipedia/commons/a/a1/StackOfScrewPiles.jpg)
Screw piles, sometimes referred to as screw-piles, screw piers, screw anchors, screw foundations, ground screws, helical piles, helical piers, or helical anchors are a steel screw-in piling and
ground anchoring system used for building
deep
Deep or The Deep may refer to:
Places United States
* Deep Creek (Appomattox River tributary), Virginia
* Deep Creek (Great Salt Lake), Idaho and Utah
* Deep Creek (Mahantango Creek tributary), Pennsylvania
* Deep Creek (Mojave River tributary), ...
foundations. Screw piles are typically manufactured from high-strength
steel using varying sizes of tubular hollow sections for the pile or anchors shaft.
The pile shaft transfers a
structure's load into the pile. Helical steel plates are
welded
Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature techniques such as braz ...
to the pile shaft in accordance with the intended ground conditions. Helices can be press-formed to a specified pitch or simply consist of flat plates welded at a specified pitch to the pile's shaft. The number of helices, their diameters and position on the pile shaft as well as steel plate thickness are all determined by a combination of:
# The combined structure design load requirement
# The
geotechnical
Geotechnical engineering is the branch of civil engineering concerned with the engineering behavior of earth materials. It uses the principles of soil mechanics and rock mechanics for the solution of its respective engineering problems. It al ...
parameters
# Environmental
corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...
parameters
# The minimum
design life
The design life of a component or product is the period of time during which the item is expected by its designers to work within its specified parameters; in other words, the life expectancy of the item. It is not always the actual length of tim ...
of the structure being supported or restrained.
Screw pile steel shaft sections are subjected to design parameters and building codes standards for the region of manufacture.
The helices that are welded over the steel shaft are also called "helical flights" or just "flights", and can vary in size depending on surface conditions.
There are a few differences between helical anchors, helical piles and helical piers, although the terms are often used interchangeably. Helical anchors consist of an extendable steel shaft with helical bearing plates. Plies or piers refer to strong base elements that withstand or transfer vertical/horizontal loads. Anchors are piles utilized only in tension applications like restraining wall tiebacks or vertical ground anchors made to resist overturning forces.
Installation
Screw piles are wound into the ground much like a screw into wood. Screw piles are installed using various earthmoving equipment fitted with rotary hydraulic attachments. Machinery varies from skid-steer
loader
Loader can refer to:
* Loader (equipment)
* Loader (computing)
** LOADER.EXE, an auto-start program loader optionally used in the startup process of Microsoft Windows ME
* Loader (surname)
* Fast loader
* Speedloader
* Boot loader
** LOADER.COM ...
s to 5 tonne through 80 tonne
excavators. Rotary hydraulic powerheads with
torque
In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of th ...
capacities ranging from 5,000 Nm to 500,000 Nm are custom fitted using various boom configurations. Special drive attachments connect the screw pile to the machine. Correct installation techniques are paramount to meet engineered design load and settlement outcomes. Incorrect techniques are likely to result in poor overall pile performance.
Development
![Screwpilediagram](https://upload.wikimedia.org/wikipedia/commons/0/0b/Screwpilediagram.gif)
Screw piles were first described by the Irish civil engineer
Alexander Mitchell in a paper in ''Civil Engineer's and Architects Journal'' in 1848 - however, helical piles had been used for almost a decade by this point.
[Howard A. Perko ''Helical Piles: A Practical Guide to Design and Installation'' John Wiley and Sons, 2009 pages 3-11] Screw foundations first appeared in the 1800s as pile foundations for lighthouses, and were extensively used for piers in harbours. Between the 1850s through 1890s, more than 100
screw-pile lighthouse
A screw-pile lighthouse is a lighthouse which stands on piles that are screwed into sandy or muddy sea or river bottoms. The first screw-pile lighthouse to begin construction was built by the blind Irish engineer Alexander Mitchell. Constructio ...
s were erected on the east coast of the United States using screw piles. Made originally from cast or wrought iron, they had limited bearing and tension capacities.
More recently,
composite
Composite or compositing may refer to:
Materials
* Composite material, a material that is made from several different substances
** Metal matrix composite, composed of metal and other parts
** Cermet, a composite of ceramic and metallic materials
...
technology has been developed and patented for use in small screw piles. Composites offer significant advantages over steel in small screw pile manufacture and installed performance.
Modern use and benefits
Screw pile are used extensively, and their usage has extended from lighthouses to rail, telecommunications, roads, and numerous other industries where fast installation is required, or building work takes place close to existing structures.
Screw pile installations have also extended to residential applications, with many homeowners choosing a screw pile over other options. Some common applications for helical pile foundations include residential decks, sheds, cement pads, preformed stairs and grade beams.
[How Screw Piles Work: https://torsionscrewpiles.ca/how-do-screw-piles-work/]
Modern screw pile design is based on standard structural and geotechnical principles. Screw pile designers typically use their own design software which has been developed through
field testing
A pilot study, pilot project, pilot test, or pilot experiment is a small-scale preliminary study conducted to evaluate feasibility, duration, cost, adverse events, and improve upon the study design prior to performance of a full-scale research pr ...
of differing compression pile and tension anchor configurations in various soil profiles. Corrosion is addressed based on extended field trials, combined with worldwide databases on steel in ground corrosion. Modern screw pile load capacities are in excess of . Large load capacity screw piles may have various components such as flat half helices, Bisalloy cutting tips and helices, cap plates or re-bar interfaces for connection to various concrete or steel structures.
Most industries use screw piling experts due to the cost efficiencies and - increasingly - the reduced environmental impact. 'Screwing' the foundations in the ground means that there is less soil displacement so excess soil does not need to be transported from the site, saving on transportation costs and reducing the
carbon footprint of the project.
The main benefits of screw pile 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, and reduced costs.
They are also suitable for both tensile and compression loads, so they are also used for masts, signs, and retaining structures.
References
https://helicalanchorsinc.com/helical-faq/ for understanding the difference of helical anchor, helical pile and helical piers
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External
* Earth Friendly Foundation Solutions
Screw Anchor
Deep foundations