Screw Piles: Design and Capacity Calculation Methods

Name and Code of Unit:
Name of the Student
Name of the Professor
City/ State
Day/Month/Year
Introduction
GEO technical engineering

In the first section of this proposal, background information on screw piles is discussed and also
the overview of the context of screw piles over stresses centered on the history and
insinuations of screw piles in regard to their merits and demerits. The proposal objectives are
also discussed followed by design essentials. Consequently, design methods are provided in this
proposal which is grouped axial capacity agenda via numerous methods, for example, individual
bearing method and cylindrical shear method. The project is concluded by comparing the two
different methods mentioned above.
Background information
Helical piles also known as screw piles are a steel screw- in pilling and ground anchoring system
which is applied in building foundations which are deep. The helical piles have been used
extensively in Western Canada to support superstructures mostly with applications in power
transmission towers, camps, and commercial buildings. The load structure is transmitted into
the pile by the shaft and the most commonly used material in the fabrication of helical piles is
steel and galvanized to repel corrosion. The invention of helical pile first took place by Irish
Engineer known as Alexander Mitchell and it was first used in the foundation system for river
moorings in 1830. Currently, the use of helical piles has adapted to the trends and engineers’
requirements (Phoon, 2008, p. 156).
The screw pile foundation is still used broadly and they usage has prolonged from lighthouses
to rail, roads, telecommunications and building work. The use of screw pile foundations is
necessary since they lessen the effect on the environment and it is cost efficiency (Prakash,
2006). Transportation of soil from the site is not a must since during screwing foundation there
GEO technical engineering

is less soil displacement. This method reduces the cost of transportation and reducing the
carbon footprint of the project.
The most important aspect of helical pile foundation include a reduction in carbon footprint,
risk reduction in the workforce, cost reduction, the project is accomplished in a shorter period,
accessibility and installation are very easy.
Summary of Helical piles and Anchors Advantages
 Can be installed in any weather
 Environmental friendly
 Quick and easy to install
 Immediate loading
 Torque-to capacity correlation.
Aims
The objective of this proposal is to deliver better precision for entirely the project approaches
available on perpendicularly encumbered screw piles and to illustrate the contrasts and
methodology description for Individual and cylindrical bearing method.
Description and Scope
Literature Review
The screw pile according to Arup Geotechnics in the year 2005, were originally applied as
anchors and hence, were centered nearby tensile loads for example buried pipelines and
GEO technical engineering

transmission towers. The applications of screw pile have increased and currently, they are used
in structures subjected to lateral and compressive loading.
There are various conditions which are hindering the performance of the screw pile, for
example, the rocky soils, boulders, and bedrocks as discussed by Schmidt and Nasr in the year
2004. The axial capacity of the piles is reduced when some piles are trimmed for installation
assistance into gravel consisting of cobbles as discovered by the Sakr (2011). There are
dissimilar methods of design namely cylindrical shear method and individual bearing method
The downward pressure known as crowd and torque is applied during installation screw pile
but the crowd effect on the design process has not been found through the piles can arrive at
their required depth as a result of an increase in the crowd as claimed by Vito and Cook (2011).
A strong ground condition is needed before installation of screw pile since in a condition like
this the theoretical and actual base pressure is substantially less as asserted by Abramson and
Yttrium (2003).
The helical plate elevates bearing capacity can be expressed using a formula as a non-
dimensional function factors as mentioned by Maruipolshii & Trofimenkov (2005). In the case of
multi-helix anchors, the most methods which are used in calculating the pullout capacity are
the cylindrical shear method and individual bearing method (Musial, 2011, p. 34).
Theoretical methods of calculating pile capacity
The soil strength, geometry of the pile, overburden pressure and embedment depth influence
the axial capacity of the helical pile.The shallow and depth failure modes can be used in
GEO technical engineering