PILE FOUNDATION

Subject : Advance Construction Equipment (2160601)

Pile foundation

• Introduction

• Use of piles

• Selection of type of pile

• Types of piles

• Pile cap and pile shoes

• Pile driving equipment and method

• Micro piling

• Pulling of piles

• Causes of failure of pile

Types of foundation

• Shallow foundation

• Deep foundation• Pile foundation

• Cofferdam foundation

• Caissons foundation

What is pile ?

• A pile is a slender structural member made of concrete, steel, wood or composite material.

• A pile is either driven into the soil or formed in-site by excavating a hole and filling it with concrete.

Pile foundation

• Pile foundation is that type of deep foundation in which the loads are taken to a low level by means of vertical members which may be▪ Timber

▪ Concrete

▪ steel

Uses of Piles

• The load of the super-structure is heavy and its distribution is uneven.

• The top soil has poor bearing capacity.

• The subsoil water is high so that pumping of water from the open trenches for the shallow foundation is difficult and uneconomical.

• Large fluctuation in subsoil water level.

• The structure is situated on sea shore or river bed, where there is danger of scouring action of water.

• Canal or deep drainage line exist near the foundation.

• For foundation of transmission towers and off-shore platforms which are subjected to uplift forces.

Scouring

Off shore platform

Transmission Tower

Factor Affecting Selection Of Type Of Piles

• Nature and type of structure• Location • Material, equipment and fund availability• Type of soil and its properties• Ground water table• Durability of pile• Length and number of pile• Case study of adjacent building• Facility for pile driving• Erosion of soil near structure

Classification of Piles

• Based on function

• Based on materials

• Based on method of installation

Based on function

• End bearing Pile

• Friction Pile

• Compaction Pile

• Tension Pile

• Anchor Pile

• Fender Pile

• Better Pile

• sheet Pile

End bearing Pile

• Penetrate through the soft soil

• Bottom or tips rest on hard strata

• Work as column

• For this pile Qu=Qpwhere, Qu=ultimate load

Qp= Pile load

Friction Pile

• Loose soil extend to a greater depth

• Pile are driven at depth when frictionresistance developed equal to load

• In that case Qu=Qs (Qs= skin friction)

• Total friction resistance can be increased• Increasing length and diameter

• Making Pile surface rough

• Placing closely or grouping of pile

Compaction Pile

• Pile do not carry any load

• For increase the bearingcapacity of soil

Tension pile

• When structure subjected to uplift due to hydrostatic pressure or over turning moment

• Also known as uplift pile

Anchor piles

• These provided anchorageagainst the horizontal pullfrom sheet pulling or anyother pulling.

Fender pile

• These are used to protectwater front structuresagainst impact from shipsor other floating objects.

Better Pile

• They are used for resistlarge horizontal forces orinclined forces.

Sheet Pile

• They are used as bulkheads or as imperviouscutoff to reduce seepageand uplift under hydraulicstructures.

• Sheet pile is classified as,1. Concrete sheet piles

2. Steel sheet pile

3. Timber sheet pile

Classification Based on Pile Material

• Concrete pile

• Steel piles

• Timber piles

• Composite pile

• Sand pile

Concrete Piles

• Pre cast piles

• Cast-in-situ

• Pre stressed

Pre Cast Concrete Pile

• It is those which are manufactured in factory or at a place away fromthe construction site and then driven into ground at the placerequired.

• It requires heavy pile driving machinery.

• It may be square, octagonal or circular in cross section.

• Size of pile vary from 30 cm to 50 cm in cross section and up to 20 mor more length.

• Grade of concrete should be M20.

Cast In Situ

• A bore is dug into the ground by inserting a casing.

• Bore is filled with cement concrete after placingreinforcement

• The casing be kept in position or it may be withdraw.

• The piles with casing are known as cased cast in situconcrete pile.

• The piles without casing are known as uncased cast in situconcrete pile.

Cased • Raymond piles

• Mac Arthur piles

• BSP base driven piles

• Swage piles

• Button bottom piles

Raymond Pile

• It used primarily as a friction pile.

• It is provided with uniform taper of 1 in 30shorter pile.

• The length of piles vary from 6 to 12 m.

• Top diameter= 40 to 60 cm.

• Bottom diameter = 20 to 30 cm

• Collapsible mandrel is driven into ground.

• When the pile is driven to the desireddepth mandrel is collapsed and withdraw.

• The shell is gradually filled with concreteup to the top.

Mac Arthur pile

• Mac Arthur is pile of uniform diameterusing the corrugated steel shell whichremain in place as in Raymond piles.

• A heavy steel casing with a core isdriven into the ground.

• When the desired depth is reached,the core is withdrawn and acorrugated steel shell is placed in thecasing.

• Concrete is placed in the shell bygradually compacting and withdrawingthe steel casing.

BSP base driven piles

• This pile consist of a helically weldedshell of steel plate.

• A concrete plug is provided at thebottom of the shell.

• Driving is done by allowing hammer tofall on the concrete plug.

• The casing is driven to the desired depthand then it is filled with concrete.

Swage piles

• It is used with advantage of driving in veryhard or it is designed to leave water tightshell for some time filling of the concrete.

• steel shell is placed on a precast concreteplug

• Pipe is driven over plug until the corereached the plug, then pipe is swage out bytapper of plug which form water tight joint.

• Pipe is driven up to specified depth by helpof driven force of core.

• Core is removed and pipe is filled withconcrete.

Button Bottom piles

• It is used where increase of end bearingarea is required.

• Pile use concrete plug shape of buttonwhich enlarge hole in soil during driving.

• It used for length up to 23 m and load upto 50 tones.

• 12 mm thick steel pipe set on concretebutton which have diameter of 25 mm.

• Pipe and button driven to specified depth.

• The casing is removed and concrete isplaced with reinforcement.

Uncased

• Simplex

• Franki

• Vibro

• Pedestal

• Pressure

Simplex Piles

• Simplex piles can be driven throughsoft or hard soil.

• Steel tube fitted with a cast ironshoe is driven into ground up todesired depth.

• If Reinforcement is necessary it putin tube then concrete is poured inpile.

• Tube is withdrawn slowly withoutconcrete being tamped.

Franki Piles

• It is used at placed where high load istransfer.(ex .marine structure)

• Plug of dry concrete is formed onground by heavy removable pipe shell.

• By help of Diesel operated hammer of20 to 30 KN weight plug is driven atdesired depth.

• Diameter of pile is 50 to 60 cm ,whileat enlargement is about 90 cm.

• Capacity of pile is 60 tones to 90 tones.

Vibro Piles

• This type of pile is best suited for places wherethe ground is soft and offers little frictionalresistance to the flow of concrete.

• Pile are formed by driving a steel tube and shoe,filling with concrete and withdraw steel tube.

• Diameter of pile 35 to 50 cm for load of 60 to 70tones. Length of pile is 25 m and above.

• Steel tube fitted with cast iron shoe by 2-2.5tone hammer by 40 blow per minute, with strokeabout 1.4 m

• When shoe and tube reached the desired leveltube is filled with concrete and tube iswithdrawn at 80 blow per minute by hammer.

• Steel tube is withdrawn leaving the shoe in placeand pile is formed with corrugation along itsheight.

Pedestal Pile

• It is used where thin bearing stratum isreached with reasonable depth.

• Pedestal pile gives the effect of spreadfooting on thin bearing stratum.

• Core and casing are driven togetherinto the ground till reached the desiredlevel.

• Core is taken out and a charge ofconcrete is placed in the tube.

• The core is again placed in the casingto rest on the top of poured concrete.

• Pressure is applied on the concretethough the core, and as the same timethe casing is withdrawn.

Pressure Pile• These piles are especially suitable for

congested site where heavy vibration andnoise are not permissible.

• Boring is done up to required depth to tube.

• After withdrawn boring tool reinforcement isplaced if required.

• A layer of concrete is laid and pressure cap isprovided at the top of tube.

• Compressed air is admitted through pipewhich cause rise the tube.

• Tube is lifted same time of concreting is doingby means of compressed air.

• Care should be taken that some portion ofconcrete remain at bottom when tube islifting for receiving new layer.

Steel Piles

• Commonly used steel piles are;▪ H-piles

▪ Box piles

▪ Tube piles

H-piles

• These pile are usually of wideflange section.

• They are suitable for trestle typestructure in which pile extendabove ground level and act ascolumn.

• They have small cross sectionarea, there for they can be easilydriven In soil.

• It used as long pile with highbearing capacity.

Box Piles

• They are rectangular oroctagonal in form filled withconcrete.

• These pile are used when notpossible to drive H-piles intohard strata.

Tube Piles

• Tubes or piles of steel are driveninto the ground.

• Concrete is filled inside the tubepiles.

• Because of circular cross sectiontube piles are easy to handleand easy to drive in.

Timber Pi les

• These pile are prepared from trunksof trees.

• They may be circular or square .

• Diameter of pile are 30 to 50 cm andlength not exceeding 20 times its topwidth.

• At bottom, a cast-iron shoe isprovided and at the top a steel plateis fixed.

• For group pile each pile is brought atsame level and concrete plate isprovided to have common platform.

Composite Pi les

• This is a type of construction inwhich piles of two differentmaterial are driven one over theother.

• They act together to perform thefunction of a single pile.

• In this pile advantage is taken ofdurability of concrete piles and thecheapest of timber pile.

• Timber pile is terminated just atthe level of ground water table.

Sand Pi les

• These pile are formed by making hole inground and fill with the sand and wellrammed.

• The sand to be used should be moist attime of placing.

• Bore hole diameter usually 30 cm. lengthof sand pile is kept about 12 times itsdiameter.

• The top of sand pile is filled withconcrete.

• Sand pile are placed at 2 to 3 m spacing.

• Load test should be carried outdetermining the bearing capacity of sandpile.

• Properly compacted sand pile can carryload up to 100 tone/m2 or more.

Classification Based on Method of Installation

• Driven pile

• Driven and cast-in-situ pile

• Bore and cast-in-situ piles

• Screw piles

• Jacked pile

Driven pile

• These pile are driven intoground by applying blow with aheavy hammer.

• Timber, steel and precastconcrete pile are installed bydriving.

Driven and cast-in-situ pile

• These pile are formed by drivinga casing with a closed bottomend into the soil .

• The casing is later filled withconcrete.

• The casing may or may not bewithdrawn.

Bore And Cast-in-Situ Piles

• These pile are formed byexcavating a hole into theground and then filling it withconcrete.

Screw Piles

Jacked pile

• These piles are jacked into theground by applying a downwardforce by a hydraulic jack.

Under Reamed Piles

• These piles are developed byC.B.R.I for serving foundation forblack cotton soils, filled up groundand other type of soil having poorbearing capacity.

Under reamed piles

• An under reamed pile is bored cast-in-situconcrete pile having one or more bulbs or underreamed in its lower level.

• The bulb or under reamed are formed by underreaming tool.

• Diameter of pile is 20 to 50 cm and bulb diameteris 2-3 times of diameter of pile.

• Length of pile is 3 to 8 m and spacing betweenpiles are 2 to 4 m.

• Load carrying capacity can increase by makingmore bulb at the base.

• The vertical spacing between two bulb is variesfrom 1.25 to 1.5 times diameter of bulb.

• For black cotton soil the bulb increase bearingcapacity and also provide anchorage againstuplift.

Construction of Under Reamed Piles

• The equipment required for the construction of pile are,1. Spiral auger - for boring

2. Under reamer - for making bulb

3. Boring guide -to keep the hole vertical

Boring Using Spiral Auger

Making Bulb Using Under Reamer

Placing of ConcretePlacing of

Reinforcement

Pile Accessories

• Pile cap

• Pile shoe

Pi le Cap

• To protect the top of pile from blowof hammer on top, pile cap isprovided.

• Pile carry load from structure anddistribute it to various pile.

• Generally, Pile cap is made of steel.Thickness and size of cap is dependon shape and size of pile hammer.

• Pile should penetrate into the capat least 10 cm length.

• For group pile a common R.C.C. isprovided for all the pile.

Pi le shoe

• Pile shoe is fitted at bottom endof pile to protect the pile and tofacilitate easy pile driving.

• Pile shoe are made of cast iron,steel or wrought iron.

• Various types of shoe are;▪Square pile shoe

▪Wedged shaped pile shoe

▪Round pile shoe

▪Steel trap pile shoe for timber pile

▪Socket type pile shoe for timber pile

▪ closed end shoe for pipe piles

P i l e d r i v i n g E q u i p m e n t

• The operation of inserting pile into ground is known as pile driving.

• Pile are driven into the ground by means of hammer.

• The equipment used for lifting hammer and allow to fall on head of pile is known as Pile driver.

• Various method for pile driving are;• Hammer driving

• Vibratory pile driver

• Watter jetting and hammering

• Partial angering method

Factor for selection of pile driving method

• Type of soil at site

• Costs of pile driving equipment

• Availability of fluid pressure

• Material of pile

• Length of pile

• Ground water level

• etc……

Hammer driving

• Equipment required for hammer driving▪ Pile frame or pile driving rig

▪ Pile hammer

▪ Leads

▪ Winches

▪ Miscellaneous equipment

Pile frame or pile

driving rig

• Pile drive with crawler mountedcrane rig commonly used for piledriving.

• The hammer is guided betweentwo parallel steel channel knownas leads.

Leads

• Leads are also called leaders.

• It is used to guide hammer andpile for alignment.

• In case of drop hammer fixedlead are used.

• Lead can be movable and can beadjusted as per the requirement.

• Movable leads are moreconvenient as they can adjustedas required.

Winches

• Winches are used for lift hammer andpile.

• It should be light with single drumprovision or heavy with double drums.

• Winches may be fitted with reversegear system.

• Winches are driven with diesel orpetrol engines or electrical power incase of drop hammer and pneumatichammers.

Pile hammer

• Types of hammer used for driving the pile are;

• Drop hammer

• Single acting hammer

• Double acting hammer

• Diesel hammer

• Vibratory hammer

1. Drop hammer

• The drop hammer is the oldest type ofhammer used pile driving.

• A drop hammer is rise by a winch andallowed to drop the top of the pileunder gravity from a certain height.

• During the driving operation a cap isfixed to the pile and cushion isgenerally provided between the pileand the cap.

• Another cushion known as hammercushion is placed on the pile cap onwhich the hammer causes the impact.

2.Single acting hammer

• In this hammer the ram is raisedby air or steam under pressure tothe required height.

• It is then allowed to fall undergravity on the top of the pile cap.

• The weight of hammer is about1000 kg to 10,000 kg.

3. Double acting hammer

• In double acting hammer raise by using air orsteam pressure and drop the hammer.

• When hammer has been raised to therequired height steam or air pressure isapplied to other side of piston and thehammer is pushed downward under pressure.

• The weight of the hammer may be about 1000kg to 2500 kg.

• It can be apply 90 to 240 blow per minute.

• It is used for driving light to moderate weightpiles in soils of average resistance againstdriving.

Vibratory hammer

Pulling Of Pile

• To replace the damaged piles during the driving operation.

• To reuse the existing piles when the structure above the pile isdemolished.

• To prepare the data of strata trough which piles are to be driven bycarrying out pulling tests.

• To remove the pile which are driven temporarily as in case of acofferdam.

Method For Pulling Of Pile

• The method for pulling of piles will depend on the type of pile, equipment availability.

• Various method are;▪ Use of double acting steam hammer

▪ Use of pile extractors

▪ Use of tongs

▪ Use of vibrator

▪ Use of electricity

Pile Extractor

Vibration Pulling

Failure of Pile

C a u s e s O f Fa i l u re O f P i l e

• Most common causes of failure of piles;

• Absence of statistical data of nature of soil strata

• Load coming on pile is high than design load.

• Bad workmanship

• Attack by insets on wood

• Breakage due to over driving (timber pile)

• Buckling of pile

• Damage due to absence of protective cover

• Improper type of pile, method of driving, classification of soil

• Insufficient reinforcement in case of R.C.C

• Misinterpretation of result from pile load test.

• Wrong formula use for determining load bearing capacity.

Causes of Failure of R.C.C. piles

• Improperly designed concrete mix.

• Use of wrong type of cement

• Insufficient concrete cover to the reinforcement

• Early removal of concrete form.

• Use of aggregate that react with the type of cement.

Micro pi l l ing

• A Micro pile is a smalldiameter, typically less than300mm.

• A drilled and grouted non-displacement pile which isheavily reinforced and carriesmost of its loading on the highcapacity steel reinforcement.

• Reinforcement and cementgrout are the majorcomponent of micro pile.

• It also known as mini pile.

Construction of micro pile

• Following step are carried out for construction of micro pile.▪ Drilling and/or installation of temporary casing

▪ Remove inner drilling bit rod.

▪ Placing reinforcement and grouting by tremie.

▪ Remove temporary casing, inject further grout under pressure.

▪ Complete pile (casing may be left in place of compressible stratum)

Application of micro pile

• For structure support• New foundation

• Under pinning of existing foundation

• Seismic retrofitting of existing structure

• Scour protection

• Excavation support in confined area

• For situ reinforcement• Slop stabilization

• Earth retention

• Ground strengthening and protection

• Settlement reduction

Advantages of micro pile

• It used to underpin the existing structure where need of minimum vibration

• It can be easily laid where low head room is constraint.

• It can be installed at any angle.

• It offers practical and cost effective solution to costly alternative pile system.

• Not require large access road or drilling platforms

Pile driving formula

• Load carrying capacity of pile can be determine following method;

1. Dynamic formula

2. Static formula

Dynamic formula

• Dynamic pile formula are useful in estimating pile capacity.

• The dynamic formula are based on assumption that the kinetic energy delivered by hammer during driving operation is equal to the work done in penetrating the pile.

Kinematic energy delivered=work done in penetration

Whηh = R x s + energy loss

➢W=weight of hammer (KN)➢h= height of fall of hammer➢ηh = Efficiency of hammer➢ R= pile resistance taken equal to Qu ➢S=penetration of pile per blow

Various Dynamic formula

• Engineering News Record (ENR) formula

• Hiley’s formula

• Danish formula

Engineering News Record formula

• As per the Engineering News formula the allowable load of driven pile is given by

Qa= Wh

F(s+c)

Qa= Allowable load in kgW = Weight of hammerh = Height of fall in mms = Final settlement per blow known as setc = Empirical constant ( drop hammer= 25 mm, single acting hammer=2.5 mm)F = Factor of safety (Usually taken as 6)

Hiley’s formula

• Hiley’s gave the formula which take into various energy loss.

Qu = Whηh

(S + C/2)Qu=ultimate load on pile

W=weight of hammer

h= Height of fall of hammer

C=elastic compression

ηh =efficiency of hammer

(drop hammer=100%,single acting hammer= 75-85 %,double acting =85%)

S= Avg. settlement per blow

Danish formula

• Qu = Whηh

(S + S0/2)

S0=Elastic compression of pile

S0={2ηh (WhL)(S + S0/2)

}1/2

L= Length of pileA= Area of cross section of pileE=Modulus of elasticity of pile material Allowable

Static Formula

• In static formula ultimate bearing capacity of pile is considered to the sum of end bearing pile and resistance of skin friction.

Qu=Qp +Qs

=qp.Ap +fs.As

Where,Qp=end bearing resistance

qp= unit end bearing resistance

Ap =area at the base

Qs= skin friction resistance

fs= unit skin friction

As= surface area

Pile load test