Pile foundation project_report

I. INTRODUCTION
The function of a Foundation is to transfer the structural loads from a building safely into the
ground. The structural loads include the dead, superimposed and wind loads. To perform the
function, the foundation must be properly designed and constructed. Its stability depends upon the
behavior under load of the soil on which it resists and this is affected partly by the design of the
foundation and partly by the characteristics of the soil.
It is necessary in the design and construction of foundation to pay attention to the nature and
strength of the materials to be used for the foundations as well as the likely behavior under load of
the soils on which the foundation rests.
II. FOUNDATIONS CLASSIFICATION
On the selection of a suitable foundation system for a building, various factors must be taken into
consideration. Among them are soil conditions, load transfer pattern, shape and size of the
building, site constraints, underground tunnels and services, environmental issues, etc. There are
two basic types of foundations :
(1)Shallow Foundations :
those that transfer loads in bearing close to the surface. They either form individual spread
footings or mat foundations, which combine the individual footings to support an
entire building or part of it. The two systems may also act in combination with each other, for
example, where a service core is seated on a large mat while the columns are founded on pad
footings.
(2) Deep Foundations : are the type of foundations distinguished from shallow foundations by the
depth they are embedded into the ground (eg. Picture 2.1). There are many reasons a geotechnical
engineer would recommend a deep foundation over a shallow foundation, but some of the common
reasons are very large design loads, a poor soil at shallow depth, or site constraints (like property
lines). There are different terms used to describe different types of deep foundations including

piles, drilled shafts, caissons and piers. The naming conventions may vary between engineering
disciplines and firms.
Picture 2.1
In the following discussion, we will examine closely pre-cast deep foundations, namely piles, the
way these are put into design, materials for piles , the construction technology and equipment used
for this type of deep foundation.
II. PILE CLASSIFICATION
The word ‘pile’ is used to describe columns, usually of reinforced concrete, driven into or cast in
the ground in order to carry foundation loads to some deep underlying firm stratum or to transmit
loads to the subsoil by the friction of their surfaces in contact with the subsoil. The main function
of a pile is to transmit loads to lower levels of ground by a combination of friction along their sides
and end bearing at the pile point or base (eg. seen in picture 3.1). Piles that transfer loads mainly

Picture 3.1
by friction to clays and silts are termed friction piles and those that mainly transfer loads by end
bearing to compactgravel, hard clay or rockare termed end-bearing piles. Four or more piles may
be used to support columns of framed structures. The columns are connected to a reinforced
concrete pile cap connected to the pile. Piles may be classified by their effect on the subsoil as
displacement piles or non-displacement piles. Displacement piles are driven, forced or cut (by an
auger) into the ground to displace subsoil. The strata are penetrated.
No soil is removed during the operation. Solid concrete or steel piles and piles formed inside tubes
which are driven into the ground and which are closed at their lower end by a shoe or plug, which
may either be left in place or extruded to form an enlarged toe, are all forms of displacement pile.
Non-displacement piles are formed by boring or other methods of excavation that do not
substantially displace subsoil. Sometimes the borehole is lined with a casing or tube that is either
left in place of extracted as the hole is filled. Driven piles are those formed by driving a precast
pile and those made by casting concrete in a hole formed by driving. Bored piles are those formed
by casting concrete in a hole previously bored or drilled in the subsoil
No soil is removed during the operation. Solid concrete or steel piles and piles formed inside tubes
which are driven into the ground and which are closed at their lower end by a shoe or plug, which
may either be left in place or extruded to form an enlarged toe, are all forms of displacement pile.
Non-displacement piles are formed by boring or other methods of excavation that do not
substantially displace subsoil. Sometimes the borehole is lined with a casing or tube that is either
left in place of extracted as the hole is filled. Driven piles are those formed by driving a precast

pile and those made by casting concrete in a hole formed by driving. Bored piles are those formed
by casting concrete in a hole previously bored or drilled in the subsoil.
(1)Timber piles : As the name implies, timber piles are piles made of wood (eg. Seen in
picture 4.1). Historically, timber has been a plentiful, locally-available resource in many
areas of the globe. Today, timber piles are still more affordable than concrete or steel.
Compared to other types of piles (steel or concrete), and depending on the source/type of
timber, timber piles may not be suitable for heavier loads (Although for instance 350 toe
diameter piles sourced from Australian hardwoods can take upward of 3500 kN for some
species).
Picture 4.1
A main consideration regarding timber piles is that they should be protected from deterioration
above groundwater level. Timber will last for a long time below the groundwater level. For timber
to deteriorate, two elements are needed: water and oxygen. Below the groundwater level, oxygen is
lacking even though there is ample water. Hence, timber tends to last for a long time below
groundwater level. It has been reported that some timber piles used during 16th century in Venice
still survive since they were below groundwater level. Timber that is to be used above the water
table can be protected from decay and insects by numerous forms of preservative treatment (ACQ,
CCA, Creosote, PEC, Copper Napthenate, etc.). Splicing timber piles is still quite common and is
the easiest of all the piling materials to splice. The normal method for splicing is by driving the
leader pile first, driving a steel tube (normally 600-1000mm long, with an internal diameter no
smaller than the minimum toe diameter) half its length onto the end of the leader pile. The follower
pile is then simply slotted into the other end of the tube and driving continues. The steel tube is

simply there to ensure that the two pieces follow each other during driving. If uplift capacity is
required, the splice can incorporate bolts, coach screws, spikes or the like to give it the necessary
capacity.
Picture 4.2
Picture 4.2.
(2)Steel piles : H-piles (eg. see in picture 4.2.1) or universal steel beam in the form of wide-
flange is commonly used. They do not cause large displacement and is useful where
upheaval of the surrounding ground is a problem. They are capable of supporting heavy
loads and can be easily cut and can be driven to great depth.
(3)Another type of steel pile foundation is the Pipe pile foundation. Piles (eg. seen in picture
4.2.2) are a good candidate for battered piles and can be driven either open end or closed
end. When driven open end, soil is allowed to enter the bottom of the pipe or tube. If an
empty pipe is required, a jet of water or an auger can be used to remove the soil inside
following driving. Closed end pipe piles are constructed by covering the bottom of the pile
with a steel plate or cast steel shoe.
(4)In some cases, pipe piles are filled with concrete to provide additional moment capacity or
corrosion resistance. In the United Kingdom, this is generally not done in order to reduce the
cost. In these cases, corrosion protection is provided by allowing for a sacrificial thickness

of steel or by adopting a higher grade of steel. If a concrete filled pipe pile is corroded, most
of the load carrying capacity of the pile will remain intact due to the concrete, while it will
be lost in an empty pipe pile. The structural capacity of pipe piles is primarily calculated
based on steel strength and concrete strength (if filled). The thickness of the steel considered
for determining capacity is typically reduced by 1/16 in. compared to the actual pipe to
account for corrosion. The amount of corrosion for a steel pipe pile can be categorized; for a
pile embedded in a non aggressive and natural soil, 0.015 mm per side per year can be
assumed from the British Steel Piling Handbook. Euro-code 3 now specifies various
corrosion rates based on the nature or soil conditions and pipe pile exposure.
(5)Steel pipe piles can either be new steel manufactured specifically for the piling industry or
reclaimed steel tubular casing previously used for other purposes such as oil and gas
picture 4.3
(6)(3) Pre-stressed concrete piles : Concrete piles are typically made with steel reinforcing
and pre-stressing tendons to obtain the tensile strength required, to survive handling and
driving, and to provide sufficient bending resistance.(eg. seen in picture 4.3.1)
Long piles can be difficult to handle and transport. Pile joints (eg. seen in picture 4.3.2) can
be used to join two or more short piles to form one long pile (eg. see in picture 4.3.3). Pile
joints can be used with both precast and pre-stressed concrete piles.

Picture 4.3.
Picture 4.3
V. DETAILED DESCRIPTION OF THE CONSTRUCTIVE PROCESS
(1) Displacement Piles.
Displacement piles refer to piles that are driven, thus displacing the soil, and include those piles
that are preformed, partially preformed or cast in place. This is the most cost efficient pilling
method but may not be 8
suitable for areas sensitive to noise, vibration and dust. The presence of boulders can also hinder
the use of driving piles.

The construction sequence of a typical precast reinforced concrete pile or a steel pile is as follows:
the determination of the cut-off levels of piles.
leader of the piling rig using a plumb or spirit level.
Picture 5.1

as a rough guide to estimate the set during driving.

25 mm thick plywood between the pile head and the helmet.

 onitor pile penetration
according to the markings on the pile. When the rate of penetration is low, monitor pile
penetration over 10 blows. Hold one end of a pencil supported firmly on a timber board not
touching the pile. The other end of the pencil marks the pile displacement on a graph paper
adhered on the pile over 10 blows.

Picture 5.1

 Stop piling if the displacement is less than the designed displacement over 10 blows.
Otherwise, continue with the piling process.
 Lengthening of a pile can be done by means of a mild steel splice sleeve and a dowel
inserted in and drilled through the centre of the pile. A splice sleeve is a mechanical coupler
for splicing reinforcing bars in precastconcrete. Reinforced bars to be spliced are inserted
halfway into the cylindrical steel sleeve. The connection is sealed with grout or epoxy resin.
It can also be done by welding the pile head/joint plate which were pre-attached to both ends
of a pile in the manufacturing process.
VI. EQUIPMENT
Picture 6.1.1 – Drop-Hammer.
Displacement piles are generally driven into the ground by holding them in the correct position
against the piling frame and applying hammer blows to the head of the pile. The basic components
of any piling frame are the vertical member that houses the leaders or guides, which in turn support
the pile and guide the hammer onto the head of the pile. Pile hammers come in a variety of types
and sizes powered by gravity, steam, compressed air or diesel.
(1) Drop Hammers : these are blocks of cast iron or steel with a mass range of 1,500 to 8,000 kg
and are raised by a cable attached to a winch. The hammer, which is
sometimes called a monkey or ram, is allowed to fall freely by gravity onto the pile head.(eg. see
in pictures 6.1.1 and 6.1.2) The free-fall distance is controllable, but generally a distance at about
1.200 m
10

is employed. Drop hammers are slower than the following power hammers and may inflict more
damage to the pile caps.
Picture
(2)Single-acting Hammers : activated by steam or compressed air, these have much the same
effect as drop hammers in that the hammer falls freely by gravity through a distance of
about 1,5000m (eg. seen in picture 6.2.1). Two types are available : in one case the hammer
is lifted by a piston rod; in the other the piston is static and the cylinder is raised and allowed
to fall freely. Both forms of hammers deliver a very powerful blow.
(3) Double-acting Hammers : these are activated by steam or compressed air, and consist of a
heavy fixed cylinder in which there is a light piston or ram that delivers a large number of rapid
light blows ( 90 to 225 blows per minute) in a short space of time, as opposed to the heavier blows
over a longer period of the drop and single-acting hammers. The object is to try to keep the pile
constantly on the move rather than being driven in a
Picture 6.1

series of jerks. This type of hammer has been replaced by the diesel hammer and by
vibrationtechniques.
Picture 6.2
(4) Diesel Hammers : (eg. seen in picture 6.2) these have been designed to give a reliable and
economic method of pile driving. Various sizes giving different energy outputs per blow are
available, but most deliver between 46 and 52 blows per minute. The hammer can be suspended
from a crane or mounted in the leaders of a piling frame. A measured amount of
liquid fuel is fed into a cup formed in the base of the cylinder. The air being compressed by the
falling ram is trapped between the ram and the anvil, which applies a preloading force to the pile.
The displaced fuel, at the precise moment of impact, results in an explosion that applies a
downward force on the pile and an upward force on the ram, which returns to its starting position
to recommence the complete cycle. The movement of the ram within the cylinder activates the
fuel supply, and opens and closes the exhaust ports. Water- or air-cooled variations exist for
popular application to vertical and inclined driving.

Picture 6.3
(5) Vibration Techniques : these can be used in driving displacement piles where soft clays,
sands and gravel are encountered. They are notably efficient, with preformed steel pipe, ‘H’ and
sheet pile sections. The equipment consists of a vibrating unit mounted on the pile head
transmitting vibrations of the required frequency and amplitude down the length of the pile shaft
(eg. seen in picture 6.5.1). It achieves this with two eccentric rotors propelled in opposite
directions to generate vertical vibrations in the pile. These are, in turn, transmitted to the
surrounding soil, reducing its shear strength and enabling the pile to sink into the subsoil under its
own weight and also that of the vibrator unit. To aid the driving process and to reduce the risk of
damage to the pile during driving, water-jetting techniques can be used. Water is directed at the
soil around the toe of the pile to loosen it and case the driving process. The water pipes are usually
attached to the perimeter of the pile shaft, and are therefore taken down with the pile as it is being
driven. The water-jetting operation is stopped before the pile reaches its final depth so that the toe
of the pile is finally embedded in undisturbed soil. The main advantage is the relatively silent
operation. Additionally there is no damage to the pile cap, and high-voltage electricity may be used
instead of combustible fuels.
To protect the heads of preformed piles from damage due to impact from hammers, various types
of protective cushioned helme
VII. QUALITY CONTROL
The main objective of forming teste piles is to confirm that the design and formation of the chosen
pile type is adequate. Pile load tests give information on the performance of the pile, installation
problems, lengths, working loads and settlements.
(1) Static Load Tests
Static load testes involve the use of a heavy load or a reaction method to counter the application of
an axial load to the top of the test pile using one or more hydraulic jacks. The main objectives are
to determine the ultimate failure load, capability of supporting a load without excessive or
continuous displacement, and to verify that the allowable loads used for the design of a pile are

appropriate and that the installation procedure is satisfactory. Two types of loading are commonly
used:
- Maintained Load Test : also referred to as working load test, of which load is increased at fixed
increments up to 1.5 to 2.5 times its working load. Settlement is recorded with respect to time of
each increment is added. Once the working load is reached, maintain the load for 12 hours.
Thereafter, reverse the load in the same increment and note the recovery.
- Ultimate Load Test : the pile is steadily jacked in to the ground at a constant rate until failure.
The ultimate bearing capacity of the pile is the load at which settlement continues to increase
without any further increase of load or the load causing a gross settlement of 10% of the pile
diameter. This is only applied to test piles which must not be used as part of the finished
foundations but should be formed and tested in such a position what will not interfere with the
actual contract but nevertheless truly representative of site conditions.
(2) Compression Load Test
As pile foundations are usually designed to carry compression loads transmitted from the
superstructure, compression load test is hence the most common test method to assess the load
carrying capacity of piles. Compressionload test can be conducted using different reaction systems
including : -
Kentledge : heavy load or kentledge comprises either stone or cast concrete blocks, pig iron
blocks, or any other suitable materials that can be safely stacked up are used to form the reaction
weight for the test (eg. seen in picture 7.2.1 and 7.2.2). The weight of the kentledge is borne on
steel or concrete cribbings. Main and secondary griders are connected to the pile head in such a
way that the load can be distributed evenly. The distance between the test pile and the supporting
cribbings should be kept as far as possible. The system should be firmly wedged, cleated or bolted
together to prevent slipping between members. The centre of gravity of the kentledge should be
aligned with that of the test pile to prevent preferential lifting on either side which may lead to
toppling. A jack is positioned between the main girder and the test pile.
- Tension Piles : (eg. seen in picture 7.2.3) a reaction system using tension piles involves two or
more tension piles to form the reaction frame. The outer tension piles are tied across their heads
with a steel or concrete beam. The object is to jack down the centre or test pile against the uplift of
the outer piles. It is preferable when possible to utilize more than two outer piles to avoid lateral
instability and to increase the pull-out resistance. It is preferable to employ four, so that a cross-
head arrangement can be used at one end of the main beam, enabling the flanges of the cross beam
to be bolted to the main loading beam.

Picture 7.2
Picture 7.3 Picture 7.4
- Ground Anchors : are useful for testing piles which are end bearing on rock. It is achieved using
sufficient number of anchor piles to provide adequate reactive capacity and a clear distance from
the test pile. The principles are similar to that of tension piles.

VIII. REHABILITATION
If the existing piles or piers are found to be deficient in vertical load capacity, the capacity can be
increased by adding additional piles or piers. If the new elements are added with an extension of
the existing cap, the existing cap may shear from the additional piles or piers. The new piles or
piers will only participate in the resistance of vertical loads subsequent to their construction. In
some cases, where the existing foundation is judged to be seriously deficient, it may be cost-
effective to provide temporary shoring to permit removal and complete replacement of the
foundation. A common problem in the seismic rehabilitation of existing buildings is uplift on the
existing foundation. If the existing piles or piers and/or their anchorages to the caps are inadequate
for the design uplift forces, new elements can be provided to resist the tensile uplift forces. If new
piles or piers are required to resist the vertical compressive forces, it may be possible to provide
the necessary uplift capacity by means of hold-downs consist of high-tensile-strength steel rods or
strands, anchored by grouting in firm material at the bottom and in the concrete cap at the top. The
existing caps need to be investigated and strengthened, if necessary, for the reverse flexural
moment resulting from the uplift forces.
Pile and pier foundations resist lateral forces by means of passive soil pressure on the caps or by
bending of the piles or piers. If the anchorage of the existing piles or piers to the caps is inadequate
or questionable in regard to development of moments in the piles or piers, passive soil pressure on
the caps may constitute the principal lateral load resistance of the foundation.
The toal resisting capacity of the foundation system will include passive pressure on tie beams and
perimeter walls extending below grade. In order to mobilize the total resisting capacity of the
existing foundation system, it is important that all of the resisting elements be properly
interconnected. This connection may be accomplished by a competent slab at or near the top of the
caps, or by adequate tie beams to affect the distribution.
If the existing total capacity is inadequate, the alternatives include enhancing the passive
resistance of the soil; increasing the contact areas of the caps, tie beams, and perimeter walls: or a
combination of these alternatives.

(1) PILE WRAPPING ( concrete pile rehabilitation ) In late 2002, the Roads and Traffic
Authority of NSW (RTA) approached CEEFC for assistance with a structural problem that is
affecting a number of its bridges. These bridges were relatively new bridges that were constructed
using concrete piles that suffered from a serious decay mechanism known as Alkali Aggregate
Reaction (AAR). This mechanism caused expansive forces within the piles which eventually led to
large cracks at the pile surface. These cracks resulted in serious corrosion of the reinforcement, in
particular in submersed piles. This mechanism was significantly well understood to be largely
prevented in new structures, but many existing bridge structures required major rehabilitation. 15
Later the Queensland Department of Transport and Main Roads also became actively involved in
this project as they have a number of bridges with similar problems. The CEEFC team developed a
fibre composite pile wrap concept that can be applied to submersed piles. The team constructed a
number of prototype pile wraps and a series of underwater trials were conducted to test the
effectiveness of the concept (eg. seen in picture 8.1.1). A special pressure test was also carried out
to establish that the concept could sustain the required high pressure loads. These tests have shown
that the wrap exceeds the stringent requirements. Large scale production techniques are currently
being developed in collaboration with a private company at the Gold Coast and installation of the
first 100 fibre composite casings at the Missingham Bridge in Northern NSW is planned for the
second half of 2004.
(2) PILE JACKET EPOXY GROUT HP ( wood pile rehabilitation )
Established in 1954, Hoffmaster’s Marina, located in Woodbridge, Virginia, evolved to
accommodate a growing boat ing business and expanding customer base of boat owners. Over this
period of time, the support piles for Hoffmaster’s two boathouses and docks underwent severe
levels of degradation due to tidal action and marine growth. Replacement costs for these structures
would have been an extremely expensive undertaking. More importantly, a shutdown required for
replacement pilings would have negatively impacted daily business operations at the marina. Five
Star Products, Inc. recommended a cost effective pile restoration solution which would ensure
durable, long term structural repair without any impact on the daily business operations at the
marina.
K&M Marine carefully scheduled the project to avoid inconveniencing the boat owners. The
jackets were brought from the storage trailer down to the pier work area. The job moved smoothly
because the jackets had been premeasured and identified to fit the specific piles in the marina.
K&M Marine proceeded to prep the jackets for installation and fill them with Pile Jacket Epoxy
Grout HP at a minimum of 12 piles every 4 days.

Picture.8.1 Picture.8.2
The Five Star Pile Jacket Epoxy Grout HP was mixed in a ChemGrout pump and pumped from the
dock into the jackets. Filling was simplified by the pre-installed 1” fittings located near the center
of the jacket which allowed for easy hose connection. Because of the flowability of the Pile Jacket
Epoxy Grout HP , and the diver’s 16
ability to easily monitor the grout filling the jacket, the pumping went very quickly and smoothly
(eg. seen in picture 8.1). Mike Weldon, the owner of K&M Marine, Inc. said “The combined
system of Pile Jacket Epoxy Grout HP and the pile jackets was the simplest and fastest he had ever
used,” and that he and his divers were looking forward to their future projects working with Five
Star® products. The repairs to the 198 piles at Hoffmaster’s Marina were finished on time (eg.
picture of finished work 8.2) and on budget due to the expertise of K&M Marine, the products
used, and the field support provided by Five Star Products. Most importantly, Hoffmaster’s
remained open every day during construction...not a single day of business was lost during the pile
repair project.

Pile foundation project_report

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