Timber piles

Piles are deep foundations which transfer the load of the superstructure deep
down in the ground. Piles are basically long slender columnar members which
transfer the load of the superstructure to the ground through skin friction or
through end bearing. A foundation is considered a pile foundation if its length
is more than three times its breadth. Piles may be made of timber, concrete, or
.steel. In this article, we are going to discuss timber piles

Timber Piles
Timber pile is a trunk of a tree, trimmed of branches. A timber pile is usually
designed for a maximum load of 15 to 25 tons/pile. Additional strength can be
obtained by bolting fish plates to its side. These piles last for about 30 years.
The breadth of these piles ranges from 12 to 16 inches.

These piles can be used as a foundation for structures with moderate load and
as a foundation for temporary structures.

Advantages of timber piles

1. The cost per running length of the pile is low. Hence these piles are economical.
2. Timber being a resilient material, timber piles are suitable for impact absorption.
3. Timber piles are easy to install.
4. If necessary, it is easy to uninstall a timber pile.
Disadvantages of timber pile
1. Timber piles have small bearing capacity.
2. Untreated timber piles above groundwater may last more than 25 years but are not
permanent.
3. Timber piles are prone to damage by hard driving.
4. Timber piles cannot be driven through hard stratum or boulders.
5. Piles of longer length may not always be available.
A timber pile must satisfy the minimum requirements before being qualified as
a foundation pile. The quality, the treatment and the constructional
characteristics of timber piles are discussed below.

Quality and Classification of Timber Piles

A timber pile should be of sound quality and free of defects. It should be
straight and have a uniform taper. A straight line drawn between the center of
the butt to the center of the tip should be contained entirely within the pile. The
quality of piles is determined by the amount or lack of defects (decay, splits,
twist of wood grains, etc.), size of knots, holes, etc.
According to ASCE Manual no 17 in the section entitled “Timber piles and
Construction Timber”, timber piles are divided into three classes on the basis of
the quality of timber and the dimensions of the piles.

Class A The minimum diameter for this class of piles is 14 inches.

pile These piles are to be used for heavy loads or large unsupported length.

Class B The minimum diameter for this class of pile ranges between 12 to 13 inches. These
pile piles are used for medium loads.

Class C The minimum diameter for this class of pile is 12 inches.

pile These piles are used for temporary structure.

Division of timber piles

Preservative Treatment
Untreated piles entirely embedded below the groundwater table are considered
permanent, provided that the marine borers are not present. When projecting
above water, the timber piles are subjected to decay by fungi and attacked by
insects and borers. Therefore, building codes usually prohibit the use of
untreated timber piles above the water table to support permanent structures.
The most effective and common method for the prevention of decay and animal
and plant attacks is the treatment of piles with preservatives like creosote oil
which is used universally. When a sufficient amount of creosote oil is
impregnated properly in the piles, the protection against decay and attack is
excellent, with the exception of few borers.
The treated piles should be handled with care. Cutting, framing, and drilling
should be done before the treatment as much as possible. Cuts, abrasions, etc
should be covered with coats of creosote.
Over-driving of Timber Piles
One of the most significant drawbacks of timber piles is the possibility of
damage due to over-driving. Piles may be damaged at the tips or above.
Providing a metal driving shoe on the tip does not materially reduce the
possibility of such damages. Therefore, the design capacity of the timber piles
is limited empirically to about 25 tons in order to avoid the possibility of
damages due to the necessity of hard-driving. Furthermore, the behavior of the
pile and the blows per foot of penetration during the pile driving operation
should be carefully observed. If there is any doubt as to the possibility of such
damage, the pile driving should be stopped immediately, and if necessary, one
.or two driven piles may be pulled out for visual examination

TIMBER PILES
Timber has been used for piled foundations for centuries. Responsibly
sourced timber piles are installed for many project types – mainly within
marine working environments and low loaded structures with a lifespan
of up to 30 years. Timber has been long favoured for marine works
because of its ability to absorb impacts and its ease of handling over
water. Timber piles are used for groynes and sea defence works as well as
jetties, dolphins, fender piling and rubbing strips. The main advantages
are potential low cost, Sustainable material, carbon sequestration, Off-
cuts can be used for fuel.
 precast concrete sheet piles
A pile is a long cylinder made up of strong material usually concrete. It is further pushed
into the ground, which gives a steady support to the structures built on top of it.

Pile structures are being used for the places where there is weak layer of soil on the
surface. Thus, it cannot support the weight of a heavy building structure. It is being used
to support concentrated loads like high-rise structures.

Piles are usually made up of wood, concrete, or steel.

What is Precast Concrete Pile
Precast concrete piles are cheap and are also known as displacement piles.

It is also the most well-known and widely used foundation method in the world. It is
usually the quickest method and also the cheapest besides the use of wooden piles.

Precast concrete piles have high resistance. Their main benefit is high vertical pile load.
The allowable capacities for the concrete piles on design build basis is from 125 to over
750 kips per pile.

Precast concrete piles are reinforced concrete piles which comes in different shapes. They
could be circular, rectangular, square, or octagonal shape.

There are two types of precast concrete piles which are as follows:

 Driven Precast concrete piles

 Bored Precast concrete piles
What is Prestressed Concrete Pile
Prestressed concrete piles play a vital role in the building structures. The primary purpose
is to carry the compression loads.

These are being used in the foundation of buildings, bridges and marine structures.

The size of the prestressed concrete piles is usually from 12 inch (305mm) 66 in
(1680mm). 12in (305mm) are usually squares piles and are used in the building
structures.  66in (1680mm) diameter are cylindrical piles, used in the marine structures
and bridges.

Advantages & Disadvantages of Precast Concrete

Piles
Advantages
i. The main advantage of the pre cast concrete piles is that these piles compact soil. Thus,
it increases the bearing capacity of the soil.
ii. These piles are available in different sizes, shapes, and lengths. They are available at
the site according to the need. As a result, it increases the speed of the work.
iii. The position of the reinforcement in the pre cast concrete piles is not disturbed or
changed
iv. Pre cast concrete piles have must faster foundation time and highest foundation
quality.
v. Pre cast concrete piles are cost effective. These are cheap and suitable to use.
vi. The method to install the pre cast concrete piling is also environmentally friendly.
vii. These are the most economic form of deep foundation and can also be driven
underwater.
viii. Pre cast concrete piles have the ability to withstand high pressure vertical loads. They
can easily bear high tension loads.
ix. These piles are resistant to the biological and chemical action from the subsoil.

Disadvantages
i. Precast concrete piles are heavy in weight. They need special type of equipment for
handling. Transportation and driving.
ii. These piles require sufficient care. If it is not provided, these may break during the
transport or driving.
iii. These piles need time to be made, which means that these would not be available on
short notice.
iv. The length of these piles is adjusted according to the transportation facilities.
v. These piles need extra reinforcement because of the transportation and driving stresses.
vi. If these piles are too long then it would be difficult to transport these. and it will be
uneconomical to cut the pile.

Size Overview
Precast concrete piles are available in different sizes which ranges from 12 to 24 in, and
in the measurements of length, these are up to about 100 fit. The load ranges from 40 to
60 tons.

If these are used for the larger sections, load will be increased and it can extend beyond
100 tons per pile.

When jetting is required for the installation of the pile, 3 to 4 in. diameter hole is formed
along the central axis of the pile.
Precast Concrete Pile Cutting Machine

Cost Overview
The cost of the concrete piles varies from region to region on the basis of quality. A
Chinese company has issued its price for 5-18m Concrete pile $1000/set.

The Precast-prestressed Concrete Institute (PCI) updated in 2021 that as the size of the
panel increases the cost becomes lower, for example, erection of 100 square feet panel
costs about $30 per square foot, whereas 200 square feet panel would cost around $20 per
square feet.
Difference Between Precast Concrete Pile and Cast in
Situ
The cost of the concrete piles varies from region to region on the basis of quality. A
Chinese company has issued its price for 5-18m Concrete pile $1000/set.

The Precast-prestressed Concrete Institute (PCI) updated in 2021 that as the size of the
panel increases the cost becomes lower, for example, erection of 100 square feet panel
costs about $30 per square foot, whereas 200 square feet panel would cost around $20 per
square feet.

Taper of Precast Concrete Pile

Precast concrete piles are manufactured in uniform cross section or tapered. The tapered
piles are usually made limited in length which is up to 40 ft.

The taper of precast concrete piles should not be more than 2cm per meter length.
Precast Concrete Pile Installation
The piles are usually driven in to the ground with the help of the hammers or vibratory
drivers. Piles can also be inserted into the ground by jetting or partial auguring.

Some types of hammers which are used for pile driving are:

 Drop hammer
 Single acting hammer
 Double acting hammer
 Diesel hammer
 Vibratory hammer

For the installation process, first of all, the site is investigated and then piles are assessed
based on strength and compressibility, etc. Groundwater level and artesian characteristics
are also checked.

To determine the level of foundation, information is collected from nearby structures and
experiences of the piles in the close area. Before the execution of the work, complete
working diagrams are prepared.

Final Thoughts
Pile foundation is a safe, sound, and dependable foundation method; it is also the oldest
method. A foundation usually consists of different layers of piles.

Pile is usually selected because of the following properties of the pile:

 Nature of the Structure

 Loading Conditions
 Type of soil and its properties
 Groundwater Table
 Facilities for pile driving
 Maintenance Cost

According to “Michael Tomlinson and John Woodward” (Author of Pile Design and
Construction Practice)– Precast concrete piles principle is best suited for the marine
structure and also proves very beneficial in the structures where timber piles are likely to
be weekend by insects.
A steel pile can be a rolled section, a fabricated shape, or a piece of sheet pile.
Two or more sections of sheet piles may be connected together in a box shape
and driven as one pile. The most important advantage of using a steel pile is its
load-carrying capacity. A steel pile can take up to 100 tons per pile. Steel piles
are most commonly used for foundations of large structures with heavy loads.

Advantages of Steel Piles:

1. Steel piles have a large bearing capacity.
2. Steel piles can penetrate through stiff layers or boulders.
3. The volume of soil displaced during the driving of steel piles is less.
4. Steel piles can withstand rough handling.

Disadvantages of Steel Piles:

1. Steel piles have a high possibility of damage from corrosion and electrolysis.
2. Steel piles are relatively expensive unless the bearing stratum can develop large
pile capacity.
3. Steel piles are less effective than friction piles.

Common types of steel Piles:

H-piles and pipe piles are the most commonly used types.

H-piles:
H-piles are proportioned, especially, to withstand the large impact stresses
during hard driving. The flanges and the web are rolled with equal thickness in
order to eliminate damage on thinner parts. The flange width is made at least
85% the depth of the pile section in order to provide rigidity in the weak axis.
Image Credits: Thearchitectdesigns.com

Pipe Piles:
Pipe piles are made of seamless or welded pipes and are frequently filled with
concrete. They may be driven closed-ended or open-ended. The open-end piles
may be driven to the desired depth, and the soil inside the pipe is cleaned out.
The closed-end piles are formed by fixing a driving point to the tip of the pile.
For major columns, the pipe piles should be at least 10 inches in diameter, and
the thickness should not be less than 5/16 inches.

The choice between the open-end and the closed-end types depends upon the
soil conditions at the site. In some cases, an open-end pipe can be driven to a
greater depth since the soil inside the pipe can be cleaned as the driving
progresses. If boulders or other obstructions are encountered before reaching
the desired depth, they may be removed by means of a chopping bit or in the
case of large diameter pipes, by blasting. In other cases where cleaning of soil
inside the pipes is difficult, closed-end pipes should be used.
 Image
Credits: https://www.flickr.com/photos/wsdot/40771196

Splices of steel piles:

H-piles are spliced in the same manner as steel columns. Welded or bolted
(high tension bolts) splice may be used depending primarily on the preference
of the engineer or the available equipment. If the splice is located above the
ground surface, or if a large bending moment will act upon the pile, the splice
should be designed to resist such stresses. In normal cases, even when the piles
are not subjected to horizontal thrust or bending moment, there is a certain
amount of bending stress in a pile. A pile is never perfectly straight and may
get bent due to driving. This can cause bending moments in the piles. Hence it
is customary to design the splice to resist a moment equal to one-third to one-
half of the moment capacity of the H-section. Some building codes require the
splice to develop the full strength of the H or pipe section. The pipe piles may
be spliced by butt welding or by use of a sleeve.

Corrosion in Steel Piles:

Corrosion is a big problem with steel piles. Following are a few methods used
to protect a steel pile from corrosion -
Additional Thickness
This method, employed by most codes, requires that the pile section contains a
certain extra thickness (usually about 1/16 inches) in excess of the sectional
area as required by strength. This may be accomplished by either deducting
1/16 inches from the actual metal thickness while computing the pile capacity
or splicing another piece of steel to the pile length where corrosive action is
anticipated.

Removal of corrosive soils

Organic soils, cinder fill, unburned carbon, or industrial waste near the ground
surface may be removed and replaced by noncorrosive soils. This method is
economical only when such soils are at shallow depths.

Concrete encasement
Near the ground surface where moisture and oxygen are abundant, the piles
may be protected very effectively by encasing with concrete. Concrete
encasement extending to a great depth is a costly method.

Cathodic Protection
Since corrosion is a continuing process of removing electrons from the piles, a
method of preventing such a removal would be effective. This is done by
cathodic method whereby a slow current is introduced towards the steel piles,
instead of away from them.

It should be pointed out here that painting or other types of coating applied
prior to driving are of doubtful value since the coating in the embedded portion
is likely to be damaged from abrasion or handling. Piles projecting into the
atmosphere should be painted periodically. Piles projecting in polluted water
should be protected with concrete encasement or coal tar paint. In fresh water,
the section near the water surface should be protected.
 fiberglass sheet piles

Fiberglass piles are structural elements made of composite materials, typically composed of
a combination of fiberglass and resin. They are used as foundation support for various types
of structures, including buildings, bridges, and offshore platforms. Fiberglass piles offer
advantages such as high strength-to-weight ratio, corrosion resistance, and low maintenance

1. Cost: Fiberglass piles are generally more expensive than traditional materials such as
wood or steel.

2. Limited Load Capacity: Fiberglass piles have a limited load capacity compared to other
materials, which may not be suitable for certain applications.

3. Brittle: Fiberglass is a brittle material and can crack or break under heavy loads or impact.

4. UV Degradation: Fiberglass is susceptible to UV degradation, which can cause it to weaken

over time.

5. Installation Challenges: The installation process for fiberglass piles can be challenging,
requiring specialized equipment and expertise.

6. Environmental Concerns: Fiberglass is not biodegradable and can pose environmental

concerns if not disposed of properly.

Limited Availability: Fiberglass piles may not be readily available in all areas, which can .7
limit their use in certain