Helical Pile Analysis and Design

This assignment focuses on the analysis and design of helical pile foundations. It requires a comprehensive understanding of helical pile behavior in different soils, including factors affecting installation, axial capacity, lateral resistance, and overall performance. Students need to evaluate relevant research papers and apply theoretical concepts to practical scenarios involving various soil types and loading conditions.

Screw Piles 1
RESEARCH PAPER ON SCREW PILES
A Research Paper on Screw Piles By
Student’s Name
Name of the Professor
Institutional Affiliation
City/State
Year/Month/Day

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TABLE OF CONTENT
Item Page
INTRODUCTION……………………………………………………………….…….4
Description……….……………………………………………………….…...5
Invention ……………………………………………………………….……...6
Applications and Uses of Screw Piles………..……………………………….…….…7
Environmental sustainability……………………………………….……………….....10
Types of Screw Piles................................................................................................…...11
Configuration of Different Screw Piles..........................................................................12
Parameters Influencing the Capacity of Piles…………………………….…….……..17
Pile anchor length……………………………………………………………..17
Pile installation torque or minimum capacity………………………………...17
Geotechnical factors…………………………………………………………..18
The usage of Screw Piles in different types of soil……………………………………25
How Screw Pile Improve the Capacity of different Types of Soil……………………29
Potential advantages of using the crew piles and helical anchors……………………..37
Disadvantages of using the screw piles……………………………………………….41
Conclusion and Recommendation………………………………………….…………43
Bibliography………………………………………………………………..…………47

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INTRODUCTION
With the growing demand for the energy in the world of today, the companies of the energy are
looking for a cheap, reliable and new system of the foundation. Nowadays many wind turbines
of the offshore have been supported on the foundation of the monopile with the structures of the
jacket being the alternative. Because of the large sizes of foundation and the equipment of the
specialist needed to piles of large diameter gives the cheap and the solution of environmental
friendliness where the piles of high capacity can be installed without difficulty from smaller
vessels hence removing issues around window weathers ad transportation. The screw piles can
also be removed after they have reached the life of service, the can be removed from the site and
deployed through the action of the simple crew. Since they have a large resistance of pulling
capacity and vertical bearing, they might be the best solution for the structures that floats for
projects of as and deepwater oil. They are commonly used for the structure of onshore as the
towers for transmission and the pipeline anchor.
Many of the piles that are used in the offshore are driven open-ended and the steel tubes and their
sizes range from the conductors' standards, diameter of 0.76m to above diameter of 6m like the
ones in the turbines of the winds. Developments in the offshore renewable have produced more
concern about the effect of the noises of underwear on different species of fish and mammals of
marine species for the driving pile for the wind turbine. The noise that is being produced when
the pile is driven should be measured and it is known that the noise of underwater is up to a
distance of 70km. it is true that the noise is audible to the mammals of the marine over the entire
range.
Many methods have been invented to mitigate the produced noise by the driving of the pile such
as the screen of noise mitigation and curtain bubbles. Screw piles are the long shaft of tubular

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diameter and small with single helix near many plates arranged at the interval on the shaft.
Helical plates enable the pile to be screwed to the placed by the application of the torque to the
shaft of the pile and this reduced the vibration and noise when fitting and reduces the
disturbances to the life of a marine. Screw piles have raised the capacity of the axial compression
when compared to the foundation of the conventional piles. The main benefit of using the screw
piles is the increase in the capacity of the uplift because of the effects of anchoring of the plates.
Also, they don’t release wastes soil, they don’t require the slurry of grout, can be used as the
piles of battered and are resistance to earthquakes and deformation.
Factors that influence the torque of installation of the pile are: the pressure of downward applied,
rate of soil advancement, level of the torque applied, installation depth, installation angle and the
type of the soil. Because of the action of push-pull, the mechanism failure covering the limit of
ultimate state response of the offshore turbines of the winds. Factors that affect the screw piles in
the uplift are geometrical properties of the screw piles, the ratio of the helix to the shaft, the
capacity of the structural type of the connection type of the helix plate. A significant aspect of
the geometry of the screw pile that has been subjected to investigations is the diameter of the
helical and the ratio between the diameter of the pile shaft and the diameter of the plate. The
torque for the installation increases with the increases in diameter of the plate, the thickness of
the plate, and plate numbers.
Screw piles are sometimes known as helical piles, screw anchor or helical anchor and are steel
crew in anchoring ground and piling systems used for constructing deep foundations. They are
valuable components in the belt of geotechnical too and can be improved to maintain many
dissimilar configurations with the more challenging condition of the subsurface. Their frequent
installation is easy and can lead to saving costs capacity and can be proved to the great point of

Screw Piles 5
certainty. The pile shaft structure’s load into the pile and screw pile plates are soldered to the
shaft pile in accordance with the condition of the ground intended. They can be designed to a
specific pitch or comprise of the flat plates welded at the identified pitches to the shaft of the
pile. Current use of the screw piles is foundations for residential and commercial building, light
standards, restoration of the failed foundations, retaining tieback walls, supports and bridge
abutments.
Description of Screw Piles
Screw piles are synthetic foundations of steel rotated to the ground to maintain the structures.
The constituents of screw piles comprise extension, lead, pile cap and plates of the helical
bearing. The first segment to the ground is the lead section, its pilot point is tapered and normally
have one or many plates of the helical bearing. The extension section advances the section of
lead deeper into the grounds till the required stratum of the bearing is attained. Extension section
may possess extra helical bearing plates but mostly are encompassed of the coupling and
dominant shaft (Abdelghany, 2012).
Screw piles have been used throughout the world in the projects and its uses such as foundations
for buildings, houses, bridges of the pedestrians, light poles and sound walls. Screw piles are also
used in the supporting essentials for the renovation of the unsuccessful foundations or to
supplement the present foundations for the support of the original load. They can be fitted at any
position or horizontally and compressive loads and tensile can be supported and are used for
retaining the systems of the walls, system of membrane roof, control of the pipeline buoyancy
and towers for transmission. The screw piles is a steel shaft with more or one helical plates
joined around (Ahmed, 2016). They are known as the deep foundation and are used to support
any type of load. The central shaft is contrived with grade tubing steel giving it high strength

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than the competition. They give many types of shaft sizes and at any type of application.
figure 1 above illustrates the screw pile (Bowles, 2013, p. 187)
Invention
The primary utilization of the screw piles was recorded in 1836 by the civil engineer called
Alexander Mitchell and blind brick maker. Being blind limited the career options of Mitchell and
took brick making and studied building construction, science, mathematics and mechanics in his
free time and his problem was how to better-fund constructions of the marine on the weak soil
like mudflats, reefs of sand and banks of river estuaries. He devised the solution to these
problems at the age of 52, the screw pile. In the beginning of 1830s, storms were frequent and
during November and October, the ranging storms cause more deaths to mariners and many
thoughts occurred to him concerning grounds of the lighthouse on the sandy beds but they
demonstrated to be unproductive in practice (Aoki, 2014).
One day in 1832, when testing with the sail that makes the boat to navigate in the wind teeth by
using wide screw pile that is flanged in water and painting screw concealed in the air. He placed
water screw on the unlimited blast of wind and ground, aggressively thrusting the crews of the
aerial canvas, entrenched the screw definitely in the ground. In 1833, he patented his discovery

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in London and named the machine screw pile and its initial use was for ship anchorage. The pile
was rotated to the ground by animals and human power by the huge handled wood wheel called a
captain. In 1838, the utilization the helical piles for the groundwork of the lighthouse of Maplin
sands on the bank close to the river entry in the UK that was not stable (Aydin, 2012).
In 1858, Eugenius birch used the technology of screw pile of Mitchell to support the seaside
piers in England, every bridge pier had interconnected columns supported by the screw pile. The
piles sustained the weight of the carts, pedestrian, the ancillary structures and building. The
foundation had to support wind loads, tidal forces and frequent flows of ice. During the
expansion of the empire of the British, the helical piles were employed to sustain fresh bridges in
numerous continents and states (Bowles, 2013).
Between the 1850s and 1890s, more than one hundred lighthouses were built on the screw piles
foundations along the Gulf of Mexico and the coast of US. From 1900 to 1950, the use of the
screw piles reduced because there were many developments in the drilling equipment and
mechanical pile driving. Deep foundations like foundations of the Raymond drilled, Franki piles,
and belled piers were established. With the establishment of the current hydraulic torque, motors
improved the manufacturing and new methods of galvanization. Hydraulic torque was present in
the 1960s which enabled easy installation of the screw piles and they became the favoured
products for resisting tensile forces. Companies of electric utilities started using the screw pile
for tie-down piles on the towers for transmission on the utility pole for the guy wire (Budhu,
2014).

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Applications and Uses of Screw Piles
Screw piles have more current applications, in the market for the electrical effectiveness, screw
piles are utilized as the guy wire anchor and foundation for the transmission towers. A solitary
screw pile has the ability to sustain the tensile load usually on the order of 25 tons and anchors
and helical piles can minimize The screw piles can also be removed after they have reached the
life of service, the can be removed from the site and deployed through the action of the simple
crew. Since they have a large resistance of pulling capacity and vertical bearing, they might be
the best solution for the structures that floats for projects of as and deepwater oil. They are
commonly used for the structure of onshore as the towers for transmission and the pipeline
anchor e the quantity of the needed concrete and hence result in the saving cost more so in the
isolated places (Canadian Geotechnical Society, 2013).
In building a house, screw piles are used in the foundation's decks, additions, and shelters to
renovate the present foundation. They are installed for the addition of the single-story mountain
home. Controllable fitting apparatus and low cost of mobilization make the screw piles ideal for
places with small access to the backyard and narrow lots. These aspects joined with the
installation speed makes the screw piles cost-effective. They are used for the decks because of
the depth and pervasiveness of the frost and one of the features of screw piles its explosive soil
and resistance to the heave of the frost (Clemence, 2014).
There are many possibilities with the screw piles in the commercial building, the little effect of
the fitting apparatus and lightweight has made the screw piles substitute for the sensitive
wetlands area in the environment. Environment walks can be made by utilizing screw pile fitting
apparatus reinforced on the finalized walkway’s portion to prevent the apparatus from disturbing

Screw Piles 9
the delicate natural area. Some of the nature walks are fitted during the winter when the ground
is frozen to lessen the effect of the installation equipment (Das, 2011).
The capability of the screw piles to be fitted without a tremor in the low bedrooms areas within
the building has increased their uses inside the building where new loads are intended. Many
advantages of the screw piles like easy to install and speed made the construction of foundation
in the retail or the building of the warehouse be done in the off hours minus disturbance of the
administrator. The area of working may be partitioned off from the remaining building areas
with the visual or dust barrier and compressed, equipment of little noise can be used
(Geotechnics, 2013).
Screw piles are utilized in supporting the staircases and elevators to fulfil the requirements of the
new moneymaking structure for a variety of usage. They are also been utilized in supporting
dense equipment for developed within the commercial building. The slim screw piles have the
high ratio of dampening for the resistance of the vibrations of the machines. They can be
combined to form the group to carry large and heavy loads for the building construction and a
minimum of three piles are used to form group top carry the loads. Three piles can support the
load up to 600 tons and in this way, they have been used in many projects of high to low
constructions and can be installed in all weather conditions (Hanna, 2015).
Screw piles are also used in excavation shoring and underground structures. They are used in the
tie backs of many systems of shoring like soldier piling and sheet piling. Screw piles may also be
utilized as the nail soil by putting the screw plates of bearing alongside the shaft length. The
main function of screw pile is to transfer the load to the soil. Currently, they are used in many
applications in lateral loads, tension and compression. The pension applications of the screw
piles include guy anchor for the towers and poles, tiebacks for permanent and temporary

Screw Piles 10
retaining walls and foundations tiebacks. They can be used in the foundations of the
underpinning sinking lifts, an element of deep foundation to support the boardwalks and
walkways, and braces of tilt-up walls. Also screw piles have become the choice of the foundation
for lateral application of load comprising stabilization of load, fences, towers, and poles (Zhang,
2010).
Environmental sustainability
Screw piles are practices of environmentally sustainable and conscientious. Their construction
needs less truck and uses less raw materials compared to other deep foundations types.
Replacement of the screw piles for other materials for deep foundations decreases the footprints
of carbon of the foundation and also reduces disturbances in the natural areas that are sensitive.
The arrangement of screw piles comprising a slender shaft and large bearing surface is a good
way to uses less raw materials. Their construction needs on order of sixty-five percent fewer raw
materials by heaviness to build than the steel screw piles and ninety-five percent fewer raw
materials by mass than the auger cast piles or drilled shafts (Zhang, 2013).
The foundation of the screw piles need few trips of the truck to and from the site of construction
and its installation need the shipping of the piles from the supplier to the place and utilization of
the machine for installation. Few truck tips mean less tear and wear of street, roads, and
highways, less pollution and less traffics. They reduce the overall footprints of carbon of the
projects, even though they are shipped for long distances to the construction site from the
supplier, the benefit is they need less raw materials by mass and fewer trips of the trucks that
reduce the intake of energy. They can also be installed with equipment with a low economy of
fuel and shorter duration than the other of deep foundations, saving fuel and reducing pollution
reduce carbon further (Vito, 2012).

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Screw piles can be used in low impact foundation projects that are sited in the sensitive areas like
historical sites, prairies, and wetlands, lightweight installation equipment reduced the
disturbances making few effects on the fragile ecosystems.
Types of Screw Piles
Shaft types of screw piles
There are four types of the screw piles available. They are explained briefly as followed
Square shaft: they are effective compared to pipe shafts with respects to the capacity gotten from
the installation energy. They will possess great axial capacity compared to the pipe shaft pile
fitted with the identical quantity of the energy of torsion into the similar soil profile. The shaft
piles are enhanced at the passing thick material compared to pipes shaft screw pipes. The cross-
sections of the square piles are slender hence, they don't have difficulty to resist fastening under
loads of compression without the soil support of surrounding. As long as there is good pressure
of the passive soil around the pile to avoid the bucking (Vickars, 2013)
Pipe shafts: these are not good in regard to the capacity of the load derived from the energy
installation but have greater sections magnitude when fastening of the square shaft or
unsubstantiated possible dimension is concerned. Their lead section doesn't penetrate dense
materials as the lead section for the square shaft.
Combo pile: a combo shafts or the combination shaft is the crew pile which possess the
advantage of the square and pipe shafts. Its section of lead is well at penetrating thick materials
and producing the capacities of the load. And is transmitted to the pipe shaft for extension of the
plain where the overload soils are soft and greater modulus sections are preferred for the
resistance of buckling or when the lateral resistance of the load is needed (Terzaghi, 2014).

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Helical pull-down micropile is a square shaft foundation with the plain section of extension
encased in the small diameter of the grout column. Pipe shafts can also be encased in less grout
column. Similar to combo, this type of screw pile also have the advantages of lead section of the
square shaft that penetrates dense materials. The added column of grout provides larger sections
modulus for the resistance of buckling and lateral resistance in the soft soil. And needs the case
of the steel. The grout in the soil develop the capacity of friction through the bond zone in a
good stratum of soil and greatly increases the total axial capacity of the pile and stiffness of the
load reaction of the pile. The pier of the grout also offers guard of the deterioration to the shaft of
steel (Tappenden, 2016).
Configuration of Different Screw Piles
There are least of one design constituent that must be put into consideration when selecting the
performance of the screw pile:
The mechanical capability of the specific screw plates: the automated strength or capacity of the
helical plate depends on the steel grade, thickness. Strength and diameter of the seal that joins it
to the pile. In most occasions, type automated capability is a distance of the helical plate
increases with the increase the shaft diameter. There should be more screw plates so the addition
of their specific capabilities may share the required pile load. The routine centred on the
requirement would need that the least quantity of the screw plates be given that is important in
sharing the load. The dimension of every plate should be left to the installation contractor as long
as the least number of given and other necessities are fulfilled like torque and least deepness
(Seider, 2015).

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The dimension of screw plates: the dimension of the screw plate can possess an important impact
on the performance and installation of the helical pile. The arrangement of the screw needed can
keep on changing. If the specifier is not happy with the performance-centered description, then
the more prescriptive strategy can be provided. This may be needed for the reasons of
comparisons and is fine as the helical plates must be. The less dense or soft the strata of
dismissing soil the greater the screw plate will require producing the capacity or torque required
(Rao, 2014).
The typical size of helical ranges from eight to fourteen in diameter and also sixteen diameters of
the plates are present. It is significant that the smallest screw is the first to penetrate the helix. A
multi-screw lead will lead to the helical increasing in dimension subsequently and the similar
helix size does not recur till the larger size accessible is attained. For instance, the configuration
of their helix would be 12'/10'/8' on every shaft sizes with squares or 14'/12'/10' helical
configuration on small shafts squares. The large square size of shafts would be used to produce
large capacities load hence are not used frequently unless they are being fitted in the dense
materials. Therefore, a smaller helix with the diameter of 8.
+ is required to penetrate dense materials appropriately. a pipe shaft has a greater area of the
cross-section which outcomes in minor area remaining of the 8 helix plate, hence the least helix
normally used on the pipe shafts is typically a diameter of 10* (Rao, 2014).
Screw plates are planes inclined and give the device of driving for the revolving progression of
the pile. Screw configuration with many screw plates drive fairer and advances properly than the
configuration of the single helix and also perfume best. If the helical plates that are used are very
few, the problem of installation that is likely to happen is spinning out and can be resolved by the
addition of many screw plates, more pressure crowd and larger helix plates. To increase the

Screw Piles 14
crowd pressure may need a large equipment like backhoe and excavators. Addition of extra
screw plates is also economical than using the large equipment (Kurian, 2012).
If numerous screw plates are employed, the issue of fitting is then the capability of the torque is
attained before reaching the required depths. The extension of helical can be eliminated by
detaching the piles, removing them out and refixing again the pile. If the screw plated on the
segment of the lead requires being detached it will need the worker of installation to stock much
dissimilar screw lead or eliminate screw plates in the ground with the saw or the torch.
Elimination of the helical plates in the ground is performed frequently but the time, cost or
motives the worker for installation would favor not removing screw plates irrespective the
technique (Schmidt, 2016).
In case there are partial risks in beyond the capacity torque of the shaft before the needed
deepness, and the penetration surpasses roughly 30', it is cost-effective to have more screw plates
to produce the capability needed in the circumstance of medium to bearing strata that is soft or to
infiltrate the bearing start in the circumstance of thick bearing strata in the start and not run the
danger of getting the length capacity of practical or revolving out when attempting to penetrates
thick materials. Removing the pile then its reinstallation to those dimensions, whereas doing able
normally have the price that surpasses the cost of giving the allowance of helical on the initial
attempt (Sego, 2016).
Penetration of different types of screw piles into desired strata of geology
Helical plates need to produce the insertion needed to progress the shaft over the profile of the
soil. The screw thread or the helical plate is the inclined plane. Piles are the dislodgment piles
with the benefit of no spoil. The soil can be moved to the side during the fitting. The smaller the

Screw Piles 15
screw pile relative to the helical plates' size the more suitable the pile will be in regard to the
volume gotten from the fitting energy. The screw pile with a smaller size of shaft relative of the
dimension of the helical plate will be best at the penetration of the thick soil than one with the
large size of shaft comparative to the helical plate size. Displacing more soil need more energy
for installation like fixing torque, the more energy for fitting the greater the equipment needed to
install the pile (Shaheen, 2015).
Square shafts are best in penetrating thick materials than the pipe shafts, where the penetration of
the materials is needed, the larger portion is required in the high position of the pile for bucking
reasons. HELICAL PULLDOWN micropile or a combo pile are good because the lead section of
the square shaft will penetrate to dense materials better than the pile with the lead of pipe shaft. if
the strata if the soil is very dense and the shaft very large in relative to the helical plate's size the
pile can whirl out meaning that the pile is interchanged however not proceeding and the torque of
installation radically dropped (Tomlinson, 2015).
Lateral loading
Screw piles whether the pipe or square pipes are normally low displacement piles. Pile's lateral
capacity depends on the flexural toughness of the pile, and soil resistance and the shaft of the pile
will be bearing in contradiction as deflected. Helical piles of low displacement don't have the
more important lateral capacity. Pile shafts and screw pulldown micropile have a small quantity,
the plastered screw pulldown shaft micropile with the casing of steel at the pile topmost gives the
stiffest section of the pile is the most opposition to the loads that are lateral (Livneh, 2013).
Potential of corrosion

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There is more information on the steel that is corrosive in piling the soil. In many occasions,
corrosion is not the practice of either pipe or square shafts. Decomposition is the member of
steel’s oxidation of the screw pile. There is usually no or little oxygen in the soils that are
disturbed mostly below the surface of water tables. Steels of the driven piles have been fitted
with the pile hummers for many centuries and are common today. Many of the bridges on the
highways in the US are bearing on steel screw piles. Types of screw piles that are encased with
the mixture of grout provides the resistance to corrosion (Pack, 2010)
Tension only loads
For members of tension, square piles are always the better choice versus energy for installation,
are good at piercing thick soils are having a small surface area for potential deterioration. There
is a steel available when the square shaft corrosion is considered. The strength and size of the
shaft are determined by the torque needed for fitting. More divisions of the steel accessible
compared to what is needed carrying the evaluated axial load tension because the steel in the
shaft is found to additional tension during connection than when in service. Once it is fitted, the
mechanical tension is controlled by the shear strength of the bolt of coupling (Meyerhof, 2014).
Reversing load
For the piles that need to resist tension and compression loads, the person designing must
identify that the screw piles are the products manufactured with the bolt connection and tolerance
should be present in every connection.
Shaft size
There are two types of designs to be considered when choosing the size of the shaft

Screw Piles 17
The torsional capacity of the shaft: the methodology of the basic screw design states that energy
for installation has the relationship to the capacity of the pile. The selected shaft must endure the
estimated torque for installation for the pile to attain the required capacity and the needed
deepness or detailed layers of the soil. If the thick layer must be penetrated before attaining the
intended depths of closure, the shaft needs to have the competent torsional capacity to pass
through the thick layers or the pre-drilling through the layers may be needed (Pack, 2014).
The axial capacity of shafts: the segment of the shaft must able to withstand the requisite axial
load which will possess a good plan to deal with the assortment of the size of shaft and type. If
the strength of torsion is enough to attain the needed capacity and depth of the interconnected
torque, the segment of the shaft will be enough to convey the axial load (Mahmoud, 2016).
Parameters Influencing the Capacity of Piles
Pile anchor length
There are 2 designs elements that should be put into consideration when estimating the length of
the pile:
Minimum length: comparative only piles, for the helical used are the piles of compression.
Usually, there is a motive of geotechnical that the screw piles be the least dimension to make
sure that the pile is bottomless to attain needed capability for an extended period of performance.
For instance, it is true that layer of the peat that is compressible occurs around 20’ from 15’
depth then it is significant for the screw piles to possess capacity bearing in the strata of the soil
beyond the layer of peat. Consequently, the least deepness should be needed to confirm that the
bearing of piles underneath the layers of peat as well as will not resolve over the period when the
consolidation of peats occurs (Klym, 2014).

Screw Piles 18
If there are no explanations of geology to need the least deep distance, the least measurement for
the pile to perform as the deep foundations are that the uppermost spiral that is the plate and is
too close to the ground is the least deepness of 5 thicknesses of the spiral below the subgrade of
the grade. If the screw plates are not fitted to this penetration the failure mode will be same to the
superficial groundwork. This can lead to the soil rapture at the ground if the confining pressures
are less, for example, if the site is composed of loose overload sand that drifts to dense medium
sands with penetration that is varying, with fewer risks of the sand becoming looser with the
increase in depth, the requirement of the smallest length may be the topmost spiral and should be
5 diameters beneath the subgrade. Many conditions simplified it to five feet below the subgrade
(Perlow, 2012).
Tension piles – the five diameter requirement over the helix of uppermost for the elements of
tension is very important. If the requirement of 5 diameters is not reached, there is no more
pressure for confining and a block or the soil plug can explode to the surface as the pile fails. For
the tiebacks piles of helical, the requirement of five diameters is 5 diameter beyond the plane of
the failure that is active, which depends on the friction, height of the wall and the angel of the
soil. It is significant the screw plates are not underlining the soil in the wedge of active
catastrophe and if it occurs, the walls can know-how the failure of global type. Also, the most
specific requirement of length for the tieback of helix should be, the topmost helix should be 5
feet past the plane of active failure. There should be the program, a formula or the table for
evaluating this in the ground to make sure that the least is gotten (Prezzi, 2016).
Cost: the entire distance fitted has the uninterrupted influence on the pile cost in both time of
installation and the cost of material and the contractor must be kept under consideration. The
length demarcated or indeterminate by the official papers that bind has big ramification on the

Screw Piles 19
costs. Binding documents that are written well should define the pile well to get the performance
of the pile required by the owner as well as obtaining the pricing of competition for the
contractor installing
Pile installation torque or minimum capacity
Whether using the prescriptive specification or performance, the capacity of pile should be
indicated to make sure that the pile desired is gotten
Minimum capacity: all the associates structured, irrespective of the way of defining the capacity
of the load or power that the associate is intended to resist, are made with the safety factor to
deliver promising situations for overloading. Or the likelihood that member is reduced for some
unpredicted reasons that are also not known, the use of normal load is known by name as
unfactored, service, working and design load (International, 2013).
The safety factor is practical to the load to give a reserve capacity load more than that which it is
estimated to see under the ordinary use. The level of protection may be recommended by the cost
of construction but is mostly left out to the record of engineers. An appropriate protection aspect
is the amalgamation of the statistics and economics. This is not economical to design from the
likelihood of zero to catastrophe, the more the improbability the higher the protection is applied
and the fewer the improbability the lower the applied factors. The standard for the industry for
screw piles is the safety factor of 2 permanent applications. The tieback pile that is going to be
tested and tensioned individually, the safety factor of 1.5 is utilized. The lower factor of safety is
acceptable because there is less improbability when the tieback is verified. The load that have
safety factor is generally known as factored load or final load (Karunasena, 2013).

Screw Piles 20
One of the serious glitches with the documents of constructions concerning the screw piles is
identifying evidently the required load. The best way to define clearly loads as factored or
ultimate load on the documents for construction. If not, then the load should be identified clearly
as the working, design, services, or unfactored loads and states clearly what the safety required
(Henry, 2012).
Installation torque: fitting torque may be indicated as the least obligation as it related to the
capacity of the pile requisite. This should be done for the piles that won't get the test of proof.
This should not be done for the tieback piles where every pile will be post-tensioned and the
proof verified. In this situation, passing the test of proof is the only way that materials and
getting less torque are actually an accessibility for the contractors to make sure that he does not
flop the test of proof. If the least approach of torque is used, the specifier should know that the
capacity of torque correlations differed depending on the size and type of the shaft used
(Mooney, 2010).
Also capacity of tension should resemble the average torque measured over the 3 averages of the
diameter of the helix of the fitted lengths. Many specifications simplify it to be 3. This is due to
the reason that in the tension, the bearing of screw plates is in contradiction of the soil that they
have passed. So depending on how quick the torque improves, it can have an important influence
on the pile’s capability (Livneh, 2013).
Design methods
Cylindrical shear methods

Screw Piles 21
This method enables approximation of the screw pile’s axial capacity. Its equation is
subsequently of the helices number, geometry of the pile, spacing of the helices and condition of
the soil.
Figure 2 above shows the model of cylindrical shear (Karunasena, 2013, p. 197)
Some of the parameters used in the calculation include the following (Hanna, 2015, p. 219).

Screw Piles 22
The bearing of Nc of different diameters of the helix is given in the table below (Livneh, 2013, p.
217)
The capacity of the uplift can be calculated by:
Nu=1.2H1/Dis equals to or less than 9, where H1 is the uppermost helix's depth and in the
cohesionless soil, the Nq value is the factor of dimensionless and varies according to the angle of
the internal friction of the soil (Mooney, 2010, p. 149).
Cohesive soil under tensile and compressive loads
The equation of the compressive soil shows the strength as the bearing function strength of the
pile end, frictional resistance produced by the interface of the soil shaft and the bearing of the
helix plate.
Qc = Qhelix+ Qshaft +Qbearing, where Qc is the capacity of the compressive ultimate pile.
Qshaft is the resistance produced on the shaft of the steel, Qbearing is the capacity bearing of
compression in the pile and Qhelix is the resistance of shearing generated on the surface of the
cylindrical failure. Thus, Qc=Sf (πDLc) Cu+AHCuNc+πdHeffαCu, where Sf is the factor of the
spacing ratio, Ah is the helix's area, and Lc is the dimension between the bottom and top helical
plates (Puri, 2015, p. 183).

Screw Piles 23
For the foundations that are shallow, the friction is known as negligible and can be expressed by:
Qc = Sf (πDLc) Cu +AHCuNc
Tensile capacity of the pile is also gotten in the same procedure to the bearing capacity of the
compression as the combination of the soil’s friction; resistance and helices’ bearing. The
difference is that tensile is used when the soil is disturbed and compression when the soil is
undisturbed.
Qt=Q shaft+Qbearing +Qhelix, thus Qt= Sf (πDLc) Cu+AH (CuNu+rH) +πdHeffαCu, where the
Qt is the tensile capacity of the pile uplift when eh friction is negligible, the equation will be
Qt=Sf (πDLc) Cu+ AH (CuNu+rH).
Cohesionless soil under uplift and compressive loading (Kurian, 2012, p. 174)
Hence,

Screw Piles 24
(Shaheen, 2015, p. 178)
Individual bearing method
It was presented as the equation showing the bearing capacity of the uplift helix pate as
the non-dimensional factors' function. It was assumed that the every late independently behaves
where the distance placed between every plate is big enough. The method of the individual
bearing mechanism of failure is explained be every helix behaving independently and hence
bearing of individual occurring in every plate when the whole ultimate capacity of the pile is
found the addition of every capacity of the individual along the resistance of the shaft. The
method of the individual bearing can be used under loads of tensile and compressive. Under
loading of compression, the factors affecting the capacity bearing will be the area of the screw
pile bearing and the soil that is not disturbed below it, although under tensile load, the capacity
of the bearing depends on the area of the pile bearing and the soil that is disturbed below it
(Perko, 2012).

Screw Piles 25
Figure above shows the forces of the method of individual bearing (Tomlinson, 2015, p. 187)
Geotechnical factors
The screw piles can be used can be used compression to support transferring load structured
through liquefiable or weal soil to hard rock or soil, and the tension to resist uplifts loads from
the structures and gives support to the retaining structures. In most cases, the fitted screw pile
have both tension and compression loads. The screws pile carrying both tension and compression
loads need to be getting deeper below soft, weak and liquefiable soils. The screw pile under the
loading of compression only need to have a good thickness of hard soil below the helix to
prevent the failure of punching. A screw pile under the loading of tension only need to have
suitable thickness if hard soil above the helix to reduce the pullout risks. Geotechnical factors
include pile deflection, pile spacing, factors of strength reduction, tension capacity, lateral
capacity, compression capacity, capacity from the installation torque, and seismic action
(Manby, 2014).

Screw Piles 26
The figure below shows simplified paths of loads (Livneh, 2013, p. 217)
Seismic consideration: there are places or regions that are fond of earthquakes and the effects of
the earthquakes shear loads are the integral consideration in the construction of built
environment. Factors to be considered are a classification of the subsoil of the site and
assessment of the potential for and the effects of cyclic softening, liquefaction, land sliding and
lateral spreading. The strength of the residual soil which affected the capacity of compression,
lateral capacity, and tension capacity of the shaft should be assessed. Where the liquefiable
layers exist the screw piles suitability will need to be assessed (Manby, 2014).
The capacity of compression: compression capacity is composed of two elements because of the
composite parts of the screw pile. Helix bearing and cylindrical friction capacity. The primary
origin of the pile capability is the capacity of the bearing of every helix plate. Where the helix is
more than one, the helices spacing on the shaft is fundamental to the all capability of the pile and
for the uppermost capacity, this will happen at the spacing of helix larger than 3 diameters. The
modifiers of the compression capacity include:
 Liquefaction: it reduces the capacity of compression the cause and extent of reduction
depending on the position of the liquefied soil relative to the founding layer. If the
liquefiable layer is below the founding layer proposed the reduced capacity id because of
the lowered capacity of bearing produced by the helix to the weak soil. If the liquefiable
layer is above the founding layer the capacity reduced will be because of the skin friction.
 Thin strong layers over weak layers: where the piles are founded in the string layer above
the layer of weak soil and the loads exceed the capacity of the layers of weak soil below,
the punching into the weak layers need to be assessed. To minimize the probability of
punching, it is recommended that the thickness of the founding layer below the lowest
helix should be five times the 5 diameters.
 Deflection of the disturbance of soil: a reduction in the capacity may be applied to
accounts for the effects of soil disturbances because of installation and pile's deflection
(Meyerhof, 2014)

Screw Piles 27
Torsional capacity: these factors are same to the factors in compression loads but have elements
of the cone and conical capacity of the pullout. The failures of the cone pull out occurs when the
reduction of shear forces occurs to zero along the plane of failure. At this point, pile and
surrounding soils are pulled out in the shape of the pyramid of the inverted truncated cone. The
pull out angle will vary according to the type of soil and lighthouse on between 0.45 to 0.55
times and the friction angle of the soil. The uplift of total tension capacity should be the smallest
of: the sum of the volumes of helix bearing plus shaft friction capacities, or the sum of the
capacity of upper helix plus cylinder friction of the helix capacity plus the capacity of shaft
friction, or the capacity of cone pull out (Karunasena, 2013).
Lateral capacity: related mechanisms of failures are overturning the failures and sliding failures.
The lateral size of the pile be influenced by;
 The strength of the soil: in the weak soil, the strength of residual spoil should be designed
appropriately and where non-liquefiable is above the liquefied soil, lateral pressure of the
soil can occur and results in deformation of the shaft pile.
 Amount of soil disturbance when installing: during installation the ground above the
upper surface of the shaft normally to the depth of 4 diameters, can be loosed and
disturbed. The reductions in the resistance of lateral over the above 4 diameters of the
screw pile installation should be applied during the phase of design.
 The degree of fixity of the pile head: pile head rotating will be high in very weak soil
leading to the lateral capacity reduction.
 Diameter, strength and length of the shaft: infilling of the concrete and pile shafts
reinforcement can improve the lateral capacity (Mitsch, 2013)
Vertical deflection: vertical moments of the screw piles occurs in the cases of loading and may
be higher than conventional bored or the driven piles. The vertical deflection arises from the soil
movement, elastic shortening of the shaft and deflection of the helix plates. The companies of
pile installation may test available data for the same piles in same profile of soil that can be used

Screw Piles 28
for comparisons. Small variations in the ground can affect the deflection of the load, where the
structure is very sensitive to vertical deflection the test should be carried out (Inc, 2013).
Pile spacing and effects of the group: the design will have to reflect whether the foundation of
the pile is acting as pile group or single. This is very relevant when the piles are spaced closer
than three to four diameter or when the compressible later underlying the bearing layer is
present. The inclination of the pile will be a way of increasing the spacing and maintaining the
capacity of vertical compression as estimated.
How Screw Piles are used in different types of soil
The following information is given to introduce soil mechanism.
Hard rock: installing the screw pile into the hard rock can results to the spin without penetrating
to form the folds below the helix and material displacement above the helix. If it cannot
penetrate the hard rock, another alternative will be required like using heads for high penetration,
changing to grouting the seat of the toe of the pile or the conventional bored piles. Screw piles
are suited to the conditions of the ground with increasing the soil strength gradually or where
there is a gradual profile of weathering at the top of the rock and in this situation, the helix will
be seated fully. That is, the lower surface will be in contact with the founding layer. Where hard
rock is overlaid by the soft soil it may not be able to seat the helix and the risk that the helix plate
will buckle is high (Klym, 2014).
liquefiable and weak soils: shafts of the screw piles are normally slender than other types of piles
foundation making them more adapted to buckling in soil that is poorly supported. When there is
need of pilling through the deep weak soils or liquefiable soils, like peat, loose sands and the soft
clay. There is the risk of buckling of the shaft. The screw piles are known as unsuitable for

Screw Piles 29
places with potential for lateral spreading originating from thick and deep well layers or the
places with no liquefiable layers (Lutenegger, 2016).
Layered soil: if the weaken soil are there either above or below the position of the helix after the
installation is complete, the values of installation torque may show a high capacity of the pile
than actually available. Monitoring the torque when installing for the last 3 diameter depth
before founding may be needed to verify the material's strength immediately above the helix to
ensure capabilities of tensions. Either the test of cone penetrometers or the boreholes below the
level of funding are recommended at the location of the critical pile to confirm that the ground
below the helix is competent (Mitsch, 2013).
Sensitive soil: the defection of large piles happens in the highly sensitive soil when restricting
forces of uplifts. This is because of the potentially disturbed matrix of the soil above the helix.in
these soil, the tolerance displacement of the structure to be supported will become an important
disuse in the designing foundation.
Soil with obstructions: suitable placement of the screw piles in the soil with many large sizes of
the particles like gravelly soils or boulders may not be possible. In this case, positional tolerance
with respect to the load transfer and structures in the cap pile will be the important issue when
designing.
How Screw Pile Improve the Capacity of different Types of Soil
Foundation exposure
The area is quarried next to the foundation to expose the feet, bottom of the grade beam and stem
wall. The area must be spacious enough to provide the safe conditions for working, usually about
15feet below the proposed elevation of the pier base bracket and at least 3 feet wide. The footing

Screw Piles 30
surface where the bracket is fitted must be smoothened using the hammer for chipping until the
surface become firm. When the foothold spreads outside the footprints of the walls supported or
other elements of the structures, it must be sufficiently serrated to enable the support to base in
the zone of influence of the load. For the concrete, the zone of influence is taken as the zone
encompasses by the estimated surface outwards and downwards at forty-five degrees from the
loaded area at the footing top to the bottom surface (Inc, 2013).
Essentials of the process
Enough knowledge of the process of design enables the understanding of how the screw pile's
design can be affected. These include the cone penetrometer test, standard penetration test,
transfer of load of screw pile that are loaded axially, process of installation and other methods of
design.
Installation process
Installation of the screw piles gives appropriate procedures and the equipment are sustained to
yield perfect outcomes. The easiness of the fitting has been the catalyst to the increasing
reputation of the screw piles, their fitting can also have challenges because of the changing of
large parts and variable conditions of the subsurface.
Equipment used during installation
The screw pile shaft is twisted to the surface by the torsion presentation by the use of the
mounted truck auger or the torque of hydraulic motor attached to the backhoe, derrick truck, skid
steer loader, front end loader, forklift or other hydraulic machines. They must be connected with
the great torque and motors of low-speed torque which enables the screw plates of bearing to

Screw Piles 31
progress with the least disruption of the soil. Torque motors used for the fitting of the screw
piles produce the torque up to 80000-foot pounds or higher (JOHNSON, 2011)
The motor torque should be should have capabilities of rotating to clockwise and anticlockwise
and should be modifiable with respect to rpm when installing. The torque motor should have the
capacity of torque equals to or higher than the least torque necessary for the project installation.
It is also advantageous if the high torque is produced by the motor of hydraulic torque is equals
the extreme torque for installation of the screw pile to avoid overloading (Livneh, 2013).
Almost any machine hydraulic can be utilized in driving the motor torque and the apparatus
required to be accorded with the torque motor's dimension. The motor torque usually has less
rate of hydraulic movement and cannot be run form the electric power pack of hydraulic hence
the speed of the hydraulic power pack rises with the increase in the flow rate of the hydraulic and
rotation rates are normally between ten to thirty rpm. The torque motors have the range of
operational pressure that is recommended and the hydraulic machine should be able to apply
torque and crowd instantaneously to confirm the ordinary progression of the screw piles. The
apparatus should be able to maintain good position and alignment of the screw pile and the
association between the torque motor and hydraulic machine should have the maximum of 23
hinges sloping ninety degrees from everyone to promote wobbling (Lutenegger, 2016).
The association between the screw piles and motor torque should be rigid and straight, and
should have the square, hexagonal or the curved adapter and the socket of the helical shaft and is
usually accomplished when the manufactured tool drive is used. The middle shaft of the screw
pile is appropriately attached to the driving tool using smoothly tapered pins of high strength
with the diameter equals to the whole size of the screw pile bolt (Vito, 2012). Hitch pins of high
strength, bolt portions not threaded, or bars of reinforcing steel not deformed are utilized for the

Screw Piles 32
drive pin. The drive pin should be ratified by the manufacturer of the screw pile and maintained
in better and safe conditions to operate nonstop. The pin should regularly be inspected for
deformations and wear and when damaged or worn, it should be substituted with the matching
pin. Some of the screw piles need more than one drive pin (Prezzi, 2016).
The useful aspects of the screw piles are that the capability can be confirmed from the torque of
installation. The connection between torque and capacity is theoretically and experimentally
recognized well. The pointer of torque should be utilized in evaluating the torque when
installing. The torque indicator can the basic portion of the equipment of installation or the
device mounted externally in line with the tooling for installation and most of them are able to
measure the increment with the accuracy of up to 500fb-lbs.mtorque indicators should be
calibrated before installation and most of them have to be standardized at the appropriate test
equipped facility. The pointers that determine the torque of the hydraulic pressure function
should be standardized with selected torque motor and hydraulic machine at the standard
temperatures of operation. They may be regulated if in the beyond engineer's doubt occurs to the
correctness of the measurement of torque (Prezzi, 2016).
The screw piles can also be fitted with motors torque activated by hands. Hands equipment for
installation need long bar reaction which stops revolution of the torque motor. The great torque
yielded by the torque motor cannot be repelled by hand. At the six foot the reaction bar is a
1000lb force at the end to stop the revolution at 6000ft-lbs, therefore, attention should be
maintained with the restorative of the rejoinder arm and should no brace against the objects that
can be become damaged or dislodged under high loads. It is not advisable to hold or stand on the
reaction bar when applying torque (Prasad, 2016).

Screw Piles 33
Attention should be maintained not to surpass the rating of the torsional power of the screw pile
during the fitting. The ratings of the torsional strength are published by the constructors of the
screw pile. Elongation of the screw hole of the coupling shaft at the tool drive should limit to
6mm or less. Screw piles with the hole of the bolt destruction surpassing the principle should not
be installed, detached, and cast-off because the elongation of the bolt holes in the direction of the
torque applied affects the power of the tensile’s shaft. If the rating of the torsional strength of the
screw pile is reached or the auguring happens before achieving minimum required depth, many
preferences:
 Converse the torque bearing, out back the screw pile a dimension of one to two feet and
try to reinstall by reducing the auguring and crowd by an obstacle and this process may
be repeated many times in the grounds with difficult conditions.
 Remove the screw pile and fit a new one with shafts of higher strength and smaller and
fewer diameter plated of the helical bearing.
 Eliminate the screw pile and predrill a smaller pilot whole distance in the similar site and
reinstall the pile. On the sites of explosive soils, the diameter of the hole of the pilot
should be same to that of the pile shaft to prevent the creation of moisture infiltration
unless grout is used.
 If the impediment is shallow, eliminate the screw pile and dislodge the obstruction by
quarry of the surface. Compress and backfill the subsequent escalation and reinstall the
pier.
 Eliminate the screw pile and transfer to a small distance to any side of the location of
installation
 Dismiss the connection at the deepness gotten and recalculate the functionality and the
pile’s capacity. Fitting of extra piles may be needed.
 Remove the helical piles and sever the uppermost bearing plate of the screw piles from
the section of the lead if more than one screw nearing plate is used, or reduce the
diameter of the screw nearing plate by cutting with the band saw. Reinstall the pile with
the configuration of the revised screw bearing plate
 Eliminate the screw pile and use a helix that is tapered like the seashell cuts to improve
the penetration in the soil that is difficult. The person installing is notified that some cuts
can be patented (Vickars, 2013).
modification of the screw bearing plates, using many piles or the configuration of a helix, stirring
a pile, or the capacity reassessment should focus to review owner's or the acceptance of engineer

Screw Piles 34
If the last torque of installation is not gotten within the practical deepness, other choices are
present:
 Till the uppermost deepness is reached, install the screw pile deeper using the section of
the additional extension.
 Add the section of extension with the screw bearing plate to decrease the bearing and
torque
 Eliminate the screw pile and fit another different one with more or higher distance plate
of the helical bearing
 Reduce the capacity of evaluated load of the screw pile and fit another screw piles at the
location recommended by the engineer
The additional extension with plates of helical bearing, downgrading the capacity of the pile,
new configurations of the helical and more screw piles should be the focus to evaluate the
owner's an engineer's approval. The initial sizing and selection of the screw pile can be done
efficiently by approximating the quantity of area of the screw bearing plates needed in a soil
to attain the pullout capacity or the bearing (Shaheen, 2015).
Tips on installation
Clear services: always clear and locate concealed values and constructions before installing
the screw pile. Potholes to locate utilities accurately closed to the planned piles
Recap invigorating the moveable motors torques: use the system of the wedge and hold to
repeat thrilling of the torque motors that are portable mostly when working in confined areas
in short session.
Crowd increase: if desired, many crowds may be gotten by safeguarding the fitting apparatus
to a screw anchor fitted as an impermanent action (Woodcock, 2013)

Screw Piles 35
Couplings difficulty: precise plump curved shafts bolt holes by eliminating the bolts of
coupling and revolving the tool drive many revolts before decoupling. Machines can also be
employed to force the extensions
Persistent hole of the bolt if significant, align the persistent bolt holes using the pin drift.
Toxic fumes: Welding, cutting, or crushing the coverings that are galvanized can produce
toxic gases. These activities should be performed on the proper safety equipment and
ventilation.
Improve the accuracy of placement: position the section of lead over the marker and with no
rotation, downward pressure can be used to push the point of the pilot into the ground until
firs screw rests on the surface of the ground. Plumpness can be checked and adjusted and
then rotation can be stated while maintaining the constant downward pressure (Lutenegger,
2016).
Screw-pile removal: when removing the screw piles, it's significant to limit the force of the
tensile applied to the pile. Some of the machines can apply excess loads of tensile to the
screw piles. The force is not limited by the machine's weight because since they are pulling
against the surface of the earth.
Penetrating bolt holes: the efficiency of many drill bits is enabled with low pressure and
speed. Drill compression can be raised using the spy bar.
Completed bolts: every side of the tubular shaft of the pile can be bored individually with the
best configuration for the finished bolt by the jig tube-shaped with the realigned guide holes.

Screw Piles 36
Torque limit: to evade the overstraining the screw pile during the fitting, it’s feasible to
install a pressure limiting device that can be adjusted along the inflow of hydraulic line
(Mooney, 2010).
Safety of installation
Proper screw pile fitting needs the minimum of two people crew: the machinist who controls the
apparatus of hydraulic and a spotter who handles the sections of the pile and for decoupling and
coupling activities. The spotters also take the measurement of the plumpness, correct positioning.
Check the torque motor alignment. Directs and observes the installation. The important factor for
the safe fitting of the screw pile is the good communication between the spotter and the operator.
Spoken instructions are not easy to hear over the noise of the hydraulic machines hence the
spotter can combine verbal cues with the hand signs (Prasad, 2016).
Transfer of the loads in piles that are loaded vertically
The design is controlled by the response of the foundations that are deep when subjected to the
loading applied hence the mechanism of load transfer of the pile is given more attention. The
forces that are practical to the screw piles when is under loading are transferred to the nearest
soil hence asserting the capacity of the pile as being the soil strength properties. Eventually, this
shows the importance of the properties of the soil, like efficient weight unit of the soil, angle of
internal friction, and the factor of the adhesion affected by the strength of the soil. During the
time of transferring loads from the pile t the soil, the load transferred to the plates in form of
resistance of bearing is always more than the resistance of the shaft.
Using the CPTs and SPTs

Screw Piles 37
The results from the SPTs have been linked with the capacity of bearing, the foundation of
settlement and soils' properties of engineering. And are based on the blows number and the value
of N. CPTs gives an overview that is continuous of the soil when analyzing. Both tests were
crucial for performing the investigation of geotechnical related to the stratigraphy of the soil to
use the results for the screw piles design. The value of N gotten from the SPTs is the important
factor because of the implications towards the density of the soil and the occurrence of the
impediments and the links to the installation speed, ultimate capacity of the screw piles and the
depth embedment of the pile. CPTs determine the properties of the soil of the profile of soil
under testing and the stratigraphy, where the resistance of the penetration measured is linked to
the need of the torque of installation and the tensile or compression pile's capacity.
Potential advantages of using the crew piles and helical anchors
The foundation types used in the areas of expansive soil depends n the potential heave estimated
Rapid installing: crew piles are usually installed using the conventional equipment for
construction like the truck excavators or the mini excavator equipped with the appropriate size of
low-speed high torque of hydraulic motors, there is no reason to mobilize the equipment like
cranes with the pile hummer or the huge bored rig shaft. This makes for inexpensive and fast
utilization. Large loads can be gotten using small connection equipment. Rates of installation are
normally on the order of six to ten revolution per minute, which means that it only takes 30
seconds. To advance the screw piles a foot or about five minutes per 10feet of length. Depending
on the section of extension, being used, the crew can attach the square shaft extension in about
one minute so as 50ft. it does not depend on the conditions of the weather even in the marginal
conditions (Das, 2011).

Screw Piles 38
Immediate load carrying capabilities: screw piles is unique compared to other types of the
systems for anchoring in that the loading can happen immediately installation. There is no need
to wait for the grout or the concrete to become hard, or when using the driven piles, no need of
waiting for dissipation of the excess pore water pressure. This can be important in some of the
projects like when the construction schedule is short and the whole projects depend on the
installation of the foundations. The conditions of soil capacity of the screw piles increase with
time as a result of the effect of ageing and thixotropic. This shows that the capacity for
installation can be lower than the long-term aged capacity which is conservative (Tappenden,
2013).
Minimal site disturbance: relative to other types of the activates of the construction regarding the
installation of the driven poles, installation crew piles, drilled shaft, anchoring systems and
helical anchors produce less disturbance of the site. Especially the fitting of the screw piles
normally produce no cutting of soil and hence can be used in the contaminated soil since the soil
do not come to the surface of the ground. This keeps the site clean, require fewer cleanups and
hence reduces the costs installation produces less noise and vibration that can be important to
other projects sensitive to the vibration of construction (Prasad, 2016).
Installation monitoring and verification of the load capacity when installing: this is possible by
using a direct torque as the pile to anchor the advances to the ground. An engineer can verify the
capacity immediately because there is connecting between the load capacity and the installation
torque. Monitoring the installation torque means that the c0pndition if the soil at every location
of installation can be verified and variability of the subsurface can be assessed, through
monitoring the torque for installation, the needed load capacity can be developed by extending
deeper to good soil by using a different pile of the geometry for anchoring. The torque for

Screw Piles 39
installation is normally used as part of criteria of termination allowance given in the specification
of the project (Shetty, 2013).
installation at the remote locations or places with limited access: screw piles are suited to the
projects in the remote areas where the cost of mobilization tend to be high and other services of
the support construction are limited or may be available readily. Some projects are congested or
are inaccessible for the construction equipment and this results in low headroom space to do the
task like inside the existing structure. They can be fabricated as a modular system comprising
extension section and the lead section that are ideal for limited access situations.
Installation in high groundwater conditions: screw piles do not need the excavation for
installation. In a situation when they are used for underpinning for the existing structures. A
shallow excavation may be required to expose the existing foundations. Difficulties are normally
experienced with shallow groundwater conditions at the sites of construction normally have less
or no impact on the installation of the screw piles. This speeds up construction and removes the
need for pumps or other methods to reduce costs and handle groundwater (Tappenden, 2016).
Easy installation on the batter: it's common to install the screw piles vertically or nay orientation
that fit the projects need. Installation of the batter like it provides more resistance for loading
laterally and for earth retaining projects, installation of the pile horizontally can be accomplished
with ease.
A simple modification of the field to increase the capacity of load: they have the ability to
modify the configuration of the elements of helical to raises the capacity of the load and this
feature makes the piles be more versatile and it is achieved by the modular nature of the
technology. Adding the extension sections with the helical plates of larger diameters is easy

Screw Piles 40
means that engineers can develop the solution quickly without the needing the fabrication on the
entire new foundation and it again shows the versatility of the technology (Manby, 2014).
A wide range of load application and soil: screw piles can be installed in a wide range of the
conditions of the subsurface, from the very soft to stiff clays and from loose to dense sand, load
design has a wide range depending on the requirement of the project.
Low footprints of carbon and a sustainable technology: manufacturer of the screw piles uses steel
of high quality that can be recycled in their fabrication. This conserves the energy and natural
resources and also reduced footprints of carbon. They are used to support the temporary
structures because they can be removed and reused with less or no change in the integrity of the
structure. This is different than a driven pile grouted anchor or the drilled shaft which often
abandoned (Woodcock, 2013).
Modular construction: the pies are fabricated in the sections resulting in the modular construction
type. This means that it is easy to reuse or extend the installation length as required to fit the
conditions of the site and the requirements of the designs.
Drilled shafts are very economical provided the caving soils and groundwater are not
encountered. When installed and designed well, resist the soil explosive. On many types of deep
foundation, drilled shaft support every type of the soil and can be made to support lateral and
very heavy loads.
Micro piles can be installed by the small apparatus the requirement of the low headroom. The
micro piles’ portion is active zone n be fixed by the permanent casing of the steel to reduce shear
when the type of the soil is expansive. Because of the large sizes of foundation and the
equipment of the specialist needed to piles of large diameter gives the cheap and the solution of

Screw Piles 41
environmental friendliness where the piles of high capacity can be installed without difficulty
from smaller vessels hence removing issues around window weathers ad transportation. The
screw piles can also be removed after they have reached the life of service, the can be removed
from the site and deployed through the action of the simple crew. Since they have a large
resistance of pulling capacity and vertical bearing, they might be the best solution for the
structures that floats for projects of as and deepwater oil. They are commonly used for the
structure of onshore as the towers for transmission and the pipeline anchor.
Helical plates enable the pile to be screwed to the placed by the application of the torque to the
shaft of the pile and this reduced the vibration and noise when fitting and reduces the
disturbances to the life of the marine. Screw piles have raised the capacity of the axial
compression when compared to the foundation of the conventional piles. The main benefit of
using the screw piles is the increase in the capacity of the uplift because of the effects of
anchoring of the plates. Also, they don't release wastes soil, they don't require the slurry of grout,
can be used as the piles of battered and are resistance to earthquakes and deformation
Limitations of using the screw piles
Limiting the conditions of the soil: screw piles are generally limited to installation ion the soil
with more grain size less than sixty percent of the helices’ pitch. They don’t advance well in
gravels and cobble deposits and should not be used. They are also not good in rocks although it
may be possible to advance the lead helical plate to bear within the first few inches of the rock
that is weathered, like profiles of the residual soil.
Limitation of the equipment: proper installation of the screw piles is good for performance. The
equipment used by the engineers should be selected to suit the expected conditions of the soil on

Screw Piles 42
the project, the specific geometry selected for the projects, and the expected high torque for the
installation. Equipment of undersized will limit the final installation and proper advance. The
rule of the thumb is that the machine’s weight should be a half ton per 1000ft-lbs of the torque of
installation that is required (Perlow, 2012).
Structural limitations: every screw pile has the structural problem that is identified by the
manufactures and is known as torque rate meaning that there is a limit to the torque that should
be applied to the screw pile before compromising the integrity of the structure. During the
installation, this limit should not be exceeded although the equipment used for installation has
more capabilities of torque. In the situation where the repeated limiting torque id reached during
the installation and the specification of installation are not met, another configuration of the crew
pile needs to be used. Screw piles are not suitable for the locations where materials pf subsurface
may damage the shaft. Soil with boulders, a lot of cobbles, gravel, and debris of construction or,
materials of the landfill are normally not good for the product of screw piles. Since the products
have large shaft lender, buckling may happen in a soft soil which cannot exert enough lateral
forces on the narrow shaft. When the soft soil is there, having the test of penetration one must
consider the axial stiffness of the shaft pile in the site (Manby, 2014).
Timber pies get destroyed easily because, of rotting in the air, as limited strength and capacity of
bearing loads. Steel piles are very expensive, is prone to corrosion, have dangers of sand
abrasion, and its section of H can twist and deflect when driving. The reinforced concrete pile is
uneasy to handle since is very heavy and sensitive to bending when being transported, installed
and hardened, it has more vibration when being driven hence the source of destruction. Cat piles
produce much noise and vibration when being driven, and is very sensitive to forces for shearing.
Conclusion and Recommendation

Screw Piles 43
This report paper is about the screw piles, it has covered the types of screw piles, design
requirements, installation and factors to consider before installation. Screw piles are sometimes
known as helical piles, screw anchor or helical anchor and are steel crew in anchoring ground
and piling systems used for constructing deep foundations. They are valuable components in the
belt of geotechnical too and may be reformed to sustain numerous dissimilar constructions with
the more challenging subsurface condition. Their frequent installation is easy and can lead to
saving costs capacity can be confirmed to the high level of inevitability.
With the growing demand for the energy in the world of today, the companies of the energy are
looking for a cheap, reliable and new system of the foundation. Nowadays many wind turbines
of the offshore have been supported on the foundation of the monopile with the structures of the
jacket being the alternative. Because of the large sizes of foundation and the equipment of the
specialist needed to piles of large diameter gives the cheap and the solution of environmental
friendliness where the piles of high capacity can be installed without difficulty from smaller
vessels hence removing issues around window weathers ad transportation.
The screw piles can also be removed after they have reached the life of service, the can be
removed from the site and deployed through the action of the simple crew. Since they have a
large resistance of pulling capacity and vertical bearing, they might be the best solution for the
structures that floats for projects of as and deepwater oil. They are commonly used for the
structure of onshore as the towers for transmission and the pipeline anchor. Many of the piles
that are used in the offshore are driven open-ended and the steel tubes and their sizes range from
the conductors' standards, the diameter of 0.76m to above diameter of 6m like the ones in the
turbines of the winds. Developments in the offshore renewable have produced more concern
about the effect of the noises of underwear on different species of fish and mammals of marine

Screw Piles 44
species for the driving pile for the wind turbine. The noise that is being produced when the pile is
driven should be measured and it is known that the noise of underwater is up to the distance of
70km. it is true that the noise is audible to the mammals of the marine over the entire range.
Many methods have been invented to mitigate the produced noise by the driving of the pile such
as the screen of noise mitigation and curtain bubbles. Screw piles are the long shaft of tubular
diameter and small with single helix near many plates arranged at the interval on the shaft.
Helical plates enable the pile to be screwed to the placed by the application of the torque to the
shaft of the pile and this reduced the vibration and noise when fitting and reduces the
disturbances to the life of a marine. Screw piles have raised the capacity of the axial compression
when compared to the foundation of the conventional piles.
The main benefit of using the screw piles is the increase in the capacity of the uplift because of
the effects of anchoring of the plates. Also, they don’t release wastes soil, they don’t require the
slurry of grout, can be used as the piles of battered and are resistance to earthquakes and
deformation. Factors that influence the torque of installation of the pile are: the pressure of
downward applied, rate of soil advancement, level of the torque applied, installation depth,
installation angle and the type of the soil. Because of the action of push-pull, the mechanism
failure covering the limit of ultimate state response of the offshore turbines of the winds. Factors
that affect the screw piles in the uplift are geometrical properties of the screw piles, the ratio of
the helix to the shaft, the capacity of the structural type of the connection type of the helix plate.
A significant aspect of the geometry of the screw pile that has been subjected to investigations is
the diameter of the helical and the ratio between the diameter of the pile shaft and the diameter of
the plate. The torque for the installation increases with the increases in diameter of the plate, the
thickness of the plate, and plate numbers.

Screw Piles 45
The pile shaft structure's load into the pile and helical plates are soldered to the shaft pile in
agreement with the condition of the ground intended. They may be pressed shaped to a specific
pitch or comprise of the plates that are flat welded at the identified pitches to the shaft of the pile.
Current use of the screw piles is foundations for residential and commercial building, light
standards, restoration of the failed foundations, retaining tieback walls, supports and bridge
abutments. Screw piles are industrial fundamentals of steel that are revolved to the ground to
upkeep the constructions. The constituents of screw piles comprise an extension, lead, pile cap
and screw bearing plates. The first segment to enter the ground is the lead section, it has a
tapered point of the pilot and normally one or many helical bearing plates.
The section of extension is used to advance the section of lead deeper into the grounds until the
required bearing stratum is attained. Section of extension can have more helical bearing plates
but mostly are comprised of the coupling and central shaft. The coupling typically consists of
female sleeves and central shaft and bolted male is normally a tubular round section or solid
square bar that is hollow. Screw piles have been throughout the world in the projects and its uses
include foundations for commercial buildings, houses, bridges of the pedestrians, light poles and
sound walls. Screw piles are also used in the underpinning elements for the repair of the failed
foundations or to augment the existing foundations for the support of the new load. They can be
fitted at any angle or horizontally and can support tensile in addition to compressive loads and
are used for retaining the systems of the walls, system of membrane roof, control of the pipeline
buoyancy and towers for transmission.
The screw piles is a steel shaft with one or more helical plates welded around. They are known
as a deep foundation and are used to support any type of load. The central shaft is fabricated with
grade steel tubing giving it high strength than the competition. They give many types of shaft

Screw Piles 46
sizes and at any type of application. Screw piles are practices of environmentally sustainable and
conscientious. Their construction needs less truck and uses less raw materials compared to other
types of deep foundations. Substitution of the screw piles for other materials for deep
foundations reduces the footprints of carbon of the foundation and also reduces disturbances in
the natural areas that are sensitive. The configuration of screw piles comprising a slender shaft
and large bearing surface is the good way to use the raw materials. Their construction needs on
order of sixty-five percent less raw materials by weight to construct compared to the steel piles
and ninety-five percent less raw materials by weight compared to the auger cast piles or drilled
shafts.
The foundation of the screw piles need few trips of the truck to and from the site of construction
and its installation need the shipping of the piles from the dealer to the site and machine
deployment for installation. Few truck tips mean less tear and wear of street, roads, and
highways, less pollution and less traffics. They reduce the overall footprints of carbon of the
projects, even though they are shipped for long distances to the construction site from the
supplier, the benefit is they need less raw materials by weight and fewer trips of the trucks that
reduce the consumption of energy. They can also be installed with equipment with a low
economy of fuel and s shorter duration than the other of deep foundations, saving fuel and
reducing pollution reduce carbon further. Screw piles can be used in low impact foundation
projects that are sited in the sensitive areas like historical sites, prairies, and wetlands,
lightweight installation equipment reduced the disturbances making few effects on the fragile
ecosystems.

Screw Piles 47
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