Helical (screw) Pile?

HELICAL (SCREW) PILES

Old Technology Re-engineered

THE TECHNOLOGY

The GTL Helical (screw) Pile foundation is an innovative and sustainable foundation solution. The helical pile, also incorrectly referred to as a screw pile, consists of a central hollow shaft of various diameters and sectional thickness, with helical plates strategically welded at given spacing. Design depth is achieved by mechanically connecting shaft sections of differing lengths which are normally governed by equipment and site restrictions. The helixes are rotated into the ground to a pre-designed depth. Each helical plate on any single pile will be the exact same pitch as one another, which minimises soil disturbance during installation compared with conventional piling techniques. The diameter of the helical plates are governed by the pre-determined loading and soil conditions. Loads are transferred to the soils by the helical plates and shaft friction. The overall number and spacing of the plates are designed to maximise the allowable load capacity of the soils. The technology of the GTL helical pile foundation is not so much in the manufacturing of the product  but rather in the specific engineering design, with the foundation being designed as a solution to a particular requirement or condition. Helical piles are referred to as small displacement piles and designed in accordance with International Standards or to the standards relevant to a specific country.
We pride ourselves on having an innovative culture where thinking outside the box is encouraged.

INTERESTING FACTS

  • IT’S NOT NEW – it is over 150 years old and has been described as one of the most underrated foundation engineering feats of the 19th century
  • The Inventor, Alexander Mitchell was an Irish bricklayer who at 21 years old became blind. He only had 4 years worth of education, however in 1937 he was elected by the ICE. He also won a Telford Medal for his invention.
  • Over 1.5 million HSP’s are installed per year in the UK, USA, China, Japan, Canada, New Zealand, Australia. This number is increasing every year.
  • The technology has been used for many high profile projects including the 2012 London Olympics, Brighton Pier, Millennium Dome to mention but a few.
  • GTL were the first company to design and install in Iraq and Kazakhstan.
  • In 1866 Helical Piles were used as a support to Brighton Pier and in 2013 GTL installed additional piles.
  • Helical piles are extremely good at with standing the affects of earthquake.
  • More than 100 screw pile lighthouses have been built along the east coast of the United States and in the Gulf of Mexico.
  • GTL are acclaimed experts in Helical pile technology and mentioned in many technical books and literature.
  • GTL have been involved, as Consultants, in producing International standards including the British Standard.

WHY OUR SOLUTION

One of the most important elements of design is to select the solution most appropriate to the specific client and project requirements. We don’t cut and paste from our last project, as every project is unique. We incorporate local knowledge and international experience to evaluate all relevant factors and predict performance to deliver the best solution. We strive on a challenge and won’t rest until we find the best possible solution that encompasses quality, economics, innovation, and efficiency ultimately to satisfy each client’s individual needs
typically, a standard 6m pile takes an average of ten minutes to install. This reduces contract time, on site preliminaries, speed to market and road/track closures amongst other factors
No currinng time so loads can be applied immediately
No spoil so no waste to muck away, which is especially beneficial with contaminated soil is present expensive cost of muck away

By reversing the installation process the helical piles can be removed and then re-used leaving a greenfield site

Less reliance on operator skills unlike a pile rig. Minimal instrumentation required to monitor pile installation which reduces human error and calibration problems

Variability in penetration depth is achieved by additional pile sections.
no requirement for full length reinforcement cages which eliminates the inherant problems.
Monitoring of soils quality and capacity during installation, direct comparison to available site investigation and preliminary pile tests.
to trees, services, existing foundations and buildings. No root damage or undermining.
the pile can be used as a tension anchor and soil nail.
unlike concrete that can only be installed above freezing point without specialist equipment.
by utilising specialist GTL equipment helical piles are able to be installed in subsea marine conditions.
equipment is delivered by a low loader
Segmented sections for reduced head heights – piles can be installed under pipe racks and in basements.
can be designed for reduced negative skin friction for collapsible soils and soils susceptible to heave/drag.
a typical crew consists of three persons. An advantage on hazardous sites where mitigating risk is paramount.
quality control of steel and fabrication gives confidence in the quality of the pile prior to installation in the ground.
the steel helix plate gives very good end bearing characteristics, with very little remoulding of the soil surface due to the installation method.
Unforeseen variability in soils can be overcome by the addition of helical plates or additional sections.
Helix plates can be spaced to give particular failure conditions (end bearing or shaft).
Installation procedure produces minimal vibration and noise, allowing installation close to noise sensitive areas and night time operations.
Reduced deliveries unlike the wet trades, means less disruption to neighbours and other on site activities.
no requirement for piling through perched water tables or underground water courses.
Preliminary Pile tests and results can be carried out and received within 48 hours of starting.
the pile can be used as a tension anchor and soil nail.
piles can protrude above ground and as such provide an elevated platform.
If a program requires acceleration then this can be achieved by deploying additional power-heads and hydraulic units.

HISTORY

The first recorded use of a helical pile was in 1836 by a blind Brick-maker and Civil Engineer named Alexander Mitchell. Mitchell was born in Ireland on April 13, 1780, and attended Belfast Academy. He lost his sight gradually from age 6 to age 21. Being blind limited Mitchell’s career options, so he took up brick making during the day and studied mechanics, mathematics, science, and building construction in his leisure time. One of the problems that puzzled Mitchell was how to better found marine structures on weak soils, such as sand reefs, mudflats, and river estuary banks. At the age of 52 Mitchell devised a solution to this problem, the helical pile. In 1833, Mitchell patented his invention in London. Mitchell called the device a “screw pile” and its first uses were for ship moorings. The pile was turned into the ground by human and animal power using a large wood handle wheel called a capstan. Screw piles on the order of 6 m long with 127-mm diameter shafts required as many as 30 men to work the capstan. Horses and donkeys were sometimes employed as well as water jets. In 1838, Mitchell used screw piles for the foundation of the Maplin Sands Lighthouse on a very unstable bank near the entrance of the river Thames in England. The foundation consisted of nine wrought-iron screw piles arranged in the form of an octagon with one screw pile in the centre. Nine piles were installed to a depth of 6.7 m by human power in nine consecutive days. In 1853, Eugenius Birch started using Mitchell’s screw pile technology to support seaside piers throughout England. The first of these was the Margate Pier. The piers themselves supported the weight of pedestrians, carts, buildings, and ancillary structures. The foundations had to support tidal forces, wind loads, and occasional ice flows. Screw piles also were used to support Blankenberg Pier in Belgium in 1895. During the expansion of the British Empire, screw piles were used to support new bridges in many countries on many continents. Technical articles were published in ‘The Engineering and Building Record’ in 1890 and in ‘Engineering News’ in 1892 regarding bridges supported on screw piles. As a result of British expansion, screw piles were soon being applied around the World. From about 1900 to 1950, the use of helical piles declined. During this time, there were major developments in mechanical pile-driving and drilling equipment. However, with the development of modern hydraulic torque motors, advances in manufacturing, and new galvanising techniques, the modern helical pile evolved primarily for anchor applications until around 1980 when engineer Stan Rupiper designed the first compression application in the U.S. using modern helical piles (Rupiper, 2000). The Helix (screw) pile design is just as effective in the 21st Century as it was back in the 19th Century. It continues to be installed throughout the World.

YOUR COMPLETE SOLUTION

Delivering projects from concept to completion