Pile foundation

By-abid khan (b.tech civil 3rd sem)

Amity School of Engineering & Technology

Summited by—mohan khantariya

Foundations• Foundations are structural components used to support

columns and transfer loads to the underlying Soil.

2

Foundations

Isolated Combined Strap wall Raft

Shallow

footing footing footing footing footing

Caissons Piles

Deep

Pile foundationPile foundations are used extensively for the

support of buildings, bridges, and other structures to safely transfer structural loads to the ground

Pile cap

PilesWeak soil

Bearing stratum

Pile foundations are used in the following situations:

1.where the soil is compressible, 2.where the soil is water logged 3.The top soil has poor bearing capacity4.The subsoil water level is highThe major uses of piles:To carry vertical compression loads,To resist uplift loadsTo resist horizontal or inclined loads

Classification of Piles

Based on the function

END BEARING PILE : These piles are used to transfer load through water or soft soil to a suitable bearing stratum.

END BEARING PILE

SOFT SO

ILFRICTION PILE:These piles are used to transfer

loads to a depth of a friction load carrying material by means of skin friction along the length of pile.

FRICTION PILE

COMPACTION PILE

COMPACTION PILE:These piles are used to compact loose soils, thus increasing their bearing capacity.

Tension pile: Tension piles are also called uplift piles.

Anchor piles: These piles are used to provide anchorage against horizontal pull from sheet piling. Fender piles and dolphins: Fender piles and dolphins are used to protect water front structure from impact of any floating object or ship.

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CLASSIFICATION OF PILESBASED ON FUNCTION

Based on the material & composition;

a. Concrete Pileb. steel pilec. timber pile

d. Composite piles

• Pre-cast Piles: Usual length: 10 m – 45 m Usual Load: 7500 kN – 8500 kN �• Cast-in-situ Piles: Usual length: 5 m – 15 m Usual Load: 200 kN – 500 kN

• Advantage� : Relatively cheap It can be easily combined with concrete superstructure Corrosion resistant It can bear hard driving • � Disadvantage: Difficult to transport Difficult to achieve desired cutoff

Concrete Pile

steel pile

• � Usual length: 15 m – 60 m �• Usual Load: 300 kN – 1200 kN• � Advantage: Relatively less hassle during installation

and easy to achieve cutoff level,High driving force may be used for fast installation, Good to penetrate hard, strata Load carrying capacity is high

• Disadvantage� : Relatively expensive Noise pollution during installation Corrosion Bend in piles while driving

Timber pile Timber piles are made from tree trunks. These piles are available in length between 4 to 6 m. timber piles are used where good bearing stratum is available at a relatively shallow depth.

Composite piles A pile which is made up of two materials like concrete and

timber or concrete and steel is called composite pile.

1. DRIVEN PILE2. Bored piles3.DRIVEN AND CAST- IN- SITU PILE

Based on the method of installation;

(i) Bored piles: Bored piles are constructed in pre-bored holes either using a casing or by circulating stabilizing agent like betonies slurry. Board piles are of following types: Small diameter piles-up to 600 mm diameter; large diameter piles-diameter greater than 600 mm; under reamed piles.

(ii) Driven piles: Driven piles may be of concrete, steel or timber. These piles are driven into the soil by the impact of hammer.

(iii) Driven and cast-in-situ piles: It is a type of driven pile. They are constructed by driving a steel casing in to the ground. The hole is then filled with concrete by placing the reinforcement and the casing is gradually fted.

Proposed by A.M. Wellington in the following general form;

Qa=

Where, Qa= allowable load W= wt. of the hammer H= height of the fall F= F.O.S, taken as “6” S= final set (penetration) C= empirical constant 2.5 for drop hammer,& 0.25 for single and double acting hammers.

Engineering News formula:

IS: 2911 gives the following formula based on the original expression of Hiley:

Qd=

Where, Qd= ultimate load on a pile C= toatal elastic compressionC = C1+C2+C3, temporary elastic compression of dolly and packing, pile & soil respectively. = efficiency of hammer=efficiency of hammer blow (i.e. ratio of energy after impact to striking energy of ram)

Hiley’s formula:

Ultimate bearing capacity of a pile is determined by the formula given below;

Qd= Rf + Rp= Asrf + Aprp

Where, Rf = total ultimate skin friction

Rp= total ultimate point or end bearing resistance As= surface area of pile upon which the skin friction acts Ap= area of cross section of pile on which bearing resistance acts rf = average skin friction

rp= unit point or toe resistance A FOS 2.5 or 3 may be adopted for finding the allowable load.

Static formula

The result of Dutch Cone Penetration Test can be applied with sufficient accuracy to determine the ultimate bearing capacity of piles in cohesion-less soils.

The following relation may be adopted:

rp= qc and,

rf= 2fc

where, qc= unit resistance of Dutch Cone Penetrometer fc= static skin friction on the shaft of the penetrometer

Penetration Test

Factors governing the selection of pilesThey are:

Length of the pile in relation to the load and type of soil, Characters of structure, Availability of the materials, Types of loading, Factors causing deterioration, Ease of maintenance, Estimated cost of types of piles, taking into account the initial

cost, life expectancy and cost of maintenance and, Availability of funds.

Selection of Pile

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Referance

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