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A Closer Look at Helical Piles

Helical piles are perfect for a variety of foundation work - see why here

Helical piles are a form of screw pile. Made up of a steel shaft and with a number of low pitched plates of a circular composition welded along the shaft, they provide the foundation and compression that ensures they can be utilised for numerous work in a whole variety of areas and across a number of industries.

A steel load transfer grillage is utilised to connect the helical piles. The piles themselves are screwed into the ground via either a hydraulic or electric drill – this can be done quickly and easily and therefore renders concrete foundations as obsolete. One of the greatest benefits of helical piles is that they are relatively inexpensive – this is partially down to the fact they are fast to install and also because they don’t require nearly as many materials for installation as a concrete or alternative form of foundation such as concrete.

Helical screw piles can be utilised for a whole variety of different work and so come in a number of different thicknesses, lengths and sizes. This allows them to be versatile, ensures they are greener than many of the other options available and lower costing. We’ve used them across a whole array of different building, civil and transport work and have achieved fantastic success in doing so.

A Quick List of the Benefits of Helical Piles

  • Easy and fast to install
  • Low cost in comparison to alternatives
  • Concrete is not required which as positive impact on cost and environmental factors
  • They can be easily reused
  • Installation is fast and also very quiet.

Who can Utilise Helical Screw Piles

We have a whole variety of different styles of helical screw piles and these can be utilised for a variety of different ground conditions and so means they are very versatile. These can be installed extremely quickly and are one of the fastest forms of foundations in existence in terms of installation time. A helical pile can also be installed quickly and quietly and doesn’t have the requirement for large machinery or issues restricting access – something cement alternatives can’t offer. This has meant that there has been a notable rise in interest in helical pile installation and is the reason the technology is increasingly popular and used widely today.

Here are some of the factors for installation

  • Utilised in all soil
  • Used at angles of up to 45 degrees
  • Fantastic for supporting structures
  • Can be used on embankments
  • Are ideal for low temperature use, unlike concrete
  • We can provide custom made solutions to fit with a variety of requirements

A helical pile provides a raft of benefits and can be utilised in a variety of foundations at a low price and with a low environmental cost. If you are interested in our helical piles then please contact us at Ground Sun – we’d love to discuss your options.

Historical Analysis

During the early development days of the screw pile anchor, the load resistance of an installed anchor couldn't be predicted with adequate accuracy. Specific information on soil conditions was missing, which meant the anchor selection was more or less a guess. With little consideration for soil variations, the effects of seasonal weather changes or drainage, soils were classified as: either sand, clay, hardpan or bog. At that time, there was not a definitive explanation for the soil conditions.

Initially, it was necessary to obtain soil samples from the anchor depth in order to classify the soil and to make anchor recommendations. However, this method was inconvenient, expensive and time-consuming. CHANCE® soil classification data enabled more accurate anchor holding capacity predictions.

Soil Probe, a Logical Development

Engineers developed the “soil test probe”, a mechanical tool which makes it possible to infer subsoil conditions from the surface of the earth. The soil test probe is screwed into the soil. As it displaces the soil, probe installation torque is measured in inch-pounds on a torque gauge, which is an essential part of the installing tool. Probe torque readings are then compared with the information on the CHANCE soil classification data chart and translated into the appropriate soil classification.

PISA®: Power-Installed Screw Anchors 

More than 50 years ago, utilizing the power of digging equipment to install screw anchors was introduced. The system consists of a screw anchor, anchor rod and a special installing wrench. Each anchor has a galvanized steel threaded anchor rod with an upset hex; single or twin helices and a galvanized guy wire nut which is screwed to the anchor rod end. Power Installed Screw Anchors (PISA®) can be installed in a matter of minutes.

Torque and Performance

Later, the installation method was improved with the development of CHANCE® torque indicators and sets of holding capacity values for given anchor types. This strengthened and simplified the soil classification data. Now, a utility employee can install a PISA anchor to a given torque value and predict, with relative accuracy, the holding capacity of the installed anchor.. The correlation between installing torque and anchor performance required thousands of tests throughout the United States. Labor, engineering, research and investments made the development of this reliable anchoring philosophy possible.

Screw anchors are designed and manufactured for maximum torsional strength. During installation, it is possible to apply more torque than the anchor alone can withstand. Some of the torque applied by the digger, and measured by installation torque indicators, is dissipated by friction along the wrench and not applied to the anchor itself.

Anchors are rated by maximum working torque or, for the more recent designs, by the 5% exclusion limit which is a more explicitly defined criterion based on statistical analysis of on-line quality control testing.

Both ratings take into consideration the variation to be expected in anchor torsional strength due to normal variations in materials and manufacturing processes. Customers should consider this variation along with the wide variation that can be seen in the frictional loss along the wrench in deciding how much torque can be applied safely during installation.

The fact that CHANCE ratings are set along the minimum credible torsional strength also should be considered in comparing CHANCE ratings to those of manufacturers who rate their anchors based on average strength.

Predicted ultimate holding capacities are based on results of extensive CHANCE tests and interpretation and are offered as an application guide only. They do not represent a guarantee of holding capacity in a particular soil class. A user must factor in his individual, appropriate safety factor.

Torque values shown are consistent values in homogeneous soils, not peak values that might occur in non-homogeneous soil. Torque values shown were obtained by averaging readings from the last two 2 feet of anchor penetration. The anchor shaft must be aligned with the guy load to prevent premature failure of the rod.