Pile foundation are essential in case where SBC is low or the load coming from superstructure is too heavy, Topics covered includes Materials used for making piles, Type of piles, load transfer mechanism, factors affecting selection of piles, Installation methods, load carrying capacity of piles, different load tests performed and the behavior of piles as a group.

1. PREPARED BY:-
YASH PATEL(151310140028)
AKASH RAO(151310140029)
MANMEET THACKER (151310140030)
RIYA TRIVEDI (151310140031)
DHRUMIL PATEL(161313140004)
Bachelor of Engineering (semester 6)- Geotechnical Engineering ||
Department of Civil & Infrastructure Engineering, AIIE.
PILE FOUNDATION

2. OUTLINE
 Introduction
 Load transfer mechanism
 Types of piles and their uses
 Factor affecting in selection of piles
 Method of installation
 Load carrying characteristics for cohsive and granular soil
 Pile subjected to vertical load- pile load carrying capacity based on static and
dynamic formulae
 Pile load test and Penetration test data

3. INTRODUCTION
 A pile is basically a long cylinder of a strong material such as concrete that is
pushed into the ground to act as a steady support for structures built on top of
it.
 Pile foundations consist of piles that are dug into the soil till a layer of stable
soil is reached.
 Pile foundations transfer building load to the bearing ground with greater
bearing capacity. Pile foundations are useful in regions with unstable upper
soil that may erode, or for large buildings.

4. WHAT IS THE USE OF PILE FOUNDATION?
 Pile foundations are principally used to transfer the loads from
superstructures, through weak, compressible strata or water onto stronger,
more compact, lesscompressible and stiffer soil or rock at depth, increasing
the effective size of a foundation and resisting horizontal loads.

5. REQUIREMENTS OF PILE FOUNDATION
 Huge vertical load with respect to soil capacity.
 Very weak soil or problematic soil.
 Huge lateral loads eg. Tower, chimneys.
 Scour depth criteria.
 For fills having very large depth.
 Uplift situations (expansive zones)
 Urban areas for future large and huge construction near the existing building.

6. FUNCTION OF PILE FOUNDATIONS
 Piles are generally used when the bearing capacity of the soil is considered to be
inadequate for the structural load of heavy construction.
 The piles transfer the load to the solid ground located at a depth.
 If the shallow soil is not stable, or the settlement estimated is not tolerable, then the
use of piles may be the only practicable solution.
 Furthermore, if the conditions of soil necessitate extensive ground development that
is expensive, the use of piles may be more economical.
 Use of piles is not only beneficial in unstable shallow soil, but also helpful in normal
ground conditions to withstand vertical and horizontal loads, or foundations over
water like jetties.

7. LOAD TRANSFER MECHANISM
 End bearing cum friction piles carry vertical compressive load partly by mean
of resistance offered by hard stratum at tip of pile and partly by friction
developed between pile shaft and soil.
 Pure friction piles carry major part of load only by friction devrlopd between
pile shaft and soil and pure end bearing piles by mean of bearing resistance at
tip of soil.
 In both the above cases lateral load are carried by lateral resistance offered by
surrounding soil.

9. TYPES OF PILES

10. CLASSIFICATION BASED ON MATERIALS
 Timber Piles
• Timber piles are made of-tree trunks driven with small end as a point
• Maximum length: 35 m; optimum length: 9 - 20m
• Max load for usual conditions: 450 kN; optimum load range = 80 - 240 kN
• Comparatively low initial cost, permanently submerged piles are resistant to decay,
easy to handle, best suited for friction piles in granular material.

13. CLASSIFICATION BASED ON MATERIALS
 Concrete Piles
• Concrete piles may be precast, prestressed, cast in place, or of composite
construction
• Precast concrete piles may be made using ordinary reinforcement or they may be
prestressed.
• Precast piles using ordinary reinforcement are designed to resist bending stresses
during picking up & transport to the site & bending moments from lateral loads and
to provide sufficient resistance to vertical loads and any tension forces developed
during driving.
• Max length: 10 - 15 m for precast, 20 - 30 m for prestressed
• Optimum length 10 - 12 m for precast. 18 - 25m prestressed

14. CONCRETE PILES
• Prestressed piles are formed by tensioning high strength steel prestress cables,
and casting the concrete about the cable. When the concrete hardens, the
prestress cables are cut, with the tension force in the cables now producing
compressive stress in the concrete pile. It is common to higher-strength concrete
(35 to 55 MPa) in prestressed piles because of the large initial compressive
stresses from prestressing. Prestressing the piles, tend to counteract any tension
stresses during either handling or driving.
• Loads for usual conditions 900 for precast. 8500 kN for prestressed
• Optimum load range: 350 - 3500 kN

16. CLASSIFICATION BASED ON MATERIALS
 Steel Piles
 Maximum length practically unlimited, optimum length: 12-50m.
 Load for usual conditions = maximum allowable stress x cross-sectional area.
 The members are usually rolled HP shapes/pipe piles. Wide flange beams & I
beams proportioned to withstand the hard driving stress to which the pile may be
subjected. In HP pile the flange thickness = web thickness, piles are either welded
or seamless steel pipes, which may be driven either open ended or closed end.
Closed end piles are usually filled with concrete after driving.
 Open end piles may be filled but this is not often necessary.

18. CLASSIFICATION BASED ON MATERIALS
 Composite Piles
 In general, a composite pile is made up of two or more sections of different
materials or different pile types.
 The upper portion could be eased cast-in-place concrete combined with a lower
portion of timber, steel H or concrete filled steel pipe pile.
 These piles have limited application and arc employed under special conditions.-

20. CLASSIFICATION BASED ON INSTALLATION TYPE
 Replacement piles
• They require a hole to be first bored into which the pile is then formed usually of
reinforced concrete.
• The shaft (bore) may be eased or uncased depending upon type of soil.
 Displacement piles
• They are usually pre-formed before being driven, jacked, screwed or hammered
into ground.
• This category consists of driven piles of steel or precast concrete and piles formed
by driving tubes or shells which are fitted with a driving shoe.
• The tubes or shells which are filled with concrete after driving.
• Also included in this category are piles formed by placing concrete as the driven
piles are withdrawn.

21. CLASSIFICATION BASED ON CONSTRUCTION METHOD
 Cast-in-situ piles
• Cast-in-situ piles are concrete pile.
• These piles are constructed by drilling holes in the ground to the required depth and
then filling the hole with concrete.
• Reinforcements are also used in the concrete as per the requirements.
• These piles are of small diameter compared to drilled piers.
• Cast-in-situ piles are straight bored piles or with one or more bulbs at intervals are
casted.
• The piles with one or more bulbs are called as under-reamed piles.

23. CLASSIFICATION BASED ON CONSTRUCTION METHOD
 Driven and cast-in-situ piles
• A steel shell of diameter of pile is driven into the ground with the aid of a mandrel
inserted into the shell.
• After driving the shell, the mandrel is removed and concrete is poured in the shell.
• The shell is made of corrugated and reinforced thin sheet steel (mono-tube piles) or
pipes (Armco welded pipes or common seamless pipes). The piles of this type are
called a shell type piles.
• The shell-less type is formed by withdrawing the shell while the concrete is being
placed.
• In both the types of piles the bottom of the shell is closed with a conical tip which
can be separated from the shell.
• This type of pile is very much used in piling over water.

25. CLASSIFICATION BASED ON LOAD TRANSFER
 End baring piles
• If a bedrock or rocklike material is present at a site within a reasonable depth, piles
can be extended to the rock surface.
• In this case, the ultimate bearing capacity of the pile depends entirely on the
underlying material; thus the piles are called end or point bearing piles.
• In most of these cases the necessary length of the pile can be fairly well
established.
• Instead of bedrock, if a fairly compact and hard stratum of soil is encountered at a
reasonable depth, piles can be extended a few meters into the hard stratum.

26. CLASSIFICATION BASED ON LOAD TRANSFER
 Friction Piles
• In these types of piles, the load on pile is resisted mainly by skin/friction resistance
along the side of the pile (pile shaft).
• Pure friction piles tend to be quite long, since the load-carrying.
• Capacity is a function of the shaft area in contact with the soil.
• In cohesion less soils, such as sands of medium to low density, friction piles are
often used to increase the density and thus the shear strength.
• When no layer of rock or rocklike material is present at a reasonable depth at a site,
point/end bearing piles become very long and uneconomical.
• For this type of subsoil condition, piles ate driven through the softer material to
specified depth.

28. INSTALLATION OF PILES
 The pile installation technique is an important feature in the design of pile foundations
that should be selected carefully by taking into consideration the resistance to
achieve the desired penetration, pile characteristics, space available at the site, and
the disturbance due to noise.
 There are two methods for installation of piles:
1.Installation by Driving
2.Installation by Boring

29. INSTALLATION OF PILES
 Some important terminologies:
 Driven pre-cast pile: The pile is castedin a yard brought to the site and driven by
some mechanism into the soil
 Driven Cast-in-situ pile: A casing plugged at bottom is driven into the ground and
then the pile is castedby removing or retaining the casing
 Bored Pre-cast pile: A bore is made and the soil inside is removed and then a pile
castedin some yard is put into the boreBored
 Cast -in-situ pile: A bore is made the soil is removed and the pile is castedat site in
the bore.

30. INSTALLATION BY DRIVING
 If the driving has to be carried out by hammer, the following factors should be take
into consideration.
 The size and weight of the pile
 The driving resistance which has to be overcome to achieve the desired penetration
 The available space and head room in the site ( because the hammer has to be
dropped from certain height and also the initial height is approximately height of the
pile + height of fall of the hammer)
 The availability of cranes
 The noise restrictions which may be in force in the locality

32. INSTALLATION BY DRIVING
 Different methods for pile driving:
• Dropping weight
• Explosion
• Vibration
• Jacking ( only for micro piles)
• Jetting

33. INSTALLATION BY BORING
 The construction of bore cast in situ concrete pile consists of following steps.
1. Location finalizing
2. Inserting temporary casing
3. Pile boring
4. Reinforcement cage lowering
5. Flushing
6. Pile concreting
7. Removal of casing

35. PILE FOUNDATIONS DESIGN
 The pile foundations should be carefully designed in accordance with the soil and
load conditions, and the cost.
 To ensure the reliability of the piles foundation that should perform as a unit, the pile
caps should be joined with beams or a reinforced concrete slab that could perform in
tension and compression.
 The piles should be designed to carry axial, shear, and bending stresses that may
develop by the relative horizontal movement of piles between the layers in the soil.
 Piles can be made from various materials, like steel, timber, and concrete, each
possessing different characteristics that should be considered

36. FACTOR INFLUENCING IN SELECTION OF PILES
Preliminary selection of piles:-
 All identified foundation alternatives should first be evaluated for suitability for the
intended application and cost.
 For piles, this evaluation should be based on
the capacity, availability, constructability, and expected performance of the
various types of piles.
 Initial evaluation of non-pile alternatives should be based on similar criteria.
 This will limit further studies to those foundation alternatives which are reasonably
feasible.
 During this initial evaluation, it may also be possible to eliminate from consideration
obvious high-cost alternatives.

37. FACTOR INFLUENCING IN SELECTION OF PILES
1. Load capacity and pile spacing
2. Type of soil
3. Type of structures in neighborhood
4. Constructability
5. Performance
6. Availability
7. Cost

38. FACTOR INFLUENCING IN SELECTION OF PILES
Final selection of pile type:-
 The final evaluation and selection should be based mainly on relative costs of the
remaining alternatives.
 This evaluation should include the costs of structural or site modifications required to
accommodate the foundation type.
 Cost and other factors may be important in the selection.
 Differences in delivery or installation schedules, levels of reliability of performance,
and potential construction complications may be considered.

39. LOAD CARRYING CAPACITY OF PILES
 The amount of load the pile can carry without undergoing continuous displacements for
insignificant load increments by virtue of its boundary condition (soil condition)and not by
virtue of its structural strength.
 The assumption for this definition is –the failure of surrounding soil occurs prior to the failure
of the pile material especially in the case of concrete piles
 The load carrying capacity of a single pile can be estimated using
• Static formulae
• Dynamic formulae
• Correlations with penetration test data
• Load tests

40. STATIC FORMULA (PILE IN GRANULAR SOIL)
(Eq. 1)

41. STATIC FORMULA (PILE IN COHESIVE SOIL)
(Eq. 2)

42. PILES IN C-Ø SOILS
(Eq. 3)

43. DYNAMIC FORMULA
 For Piles driven in soils there are a set of formulae based on the so-called Engineering News
(1888) formula.
(Eq. 4)

44. HILEY’S MODIFICATION OF WELLINGTON’S FORMULA
(Eq. 5)

45. PILE PENETRATION TEST DATA
 Static cone penetration test data and standard penetration test data are often used to determine
the pile load capacity.
 The point resistance of driven piles in sand including H piles, can also be determined using N
values as per the below equation.
 where N is thestandard penetration resistanceas observed in the field for bearing stratum
without the overburden corrections.

46. PILE PENETRATION TEST DATA
 Data from a static cone penetration test can be used to estimate the unit skin friction.
 f = aqc
 where, qc= static cone resistance in kg/cm2and a is coefficient whose value depends on the soil
type(0.04 to 0.08 for clays, 0.01 to 0.04 for silty sands, 0.01 to 0.02 for sands).
 The maximum unit skin friction for steel H-piles is taken as 0.5kg/cm2 and for driven concrete
piles it is 1.0kg/cm2

47. PILE LOAD TEST
 Vertical Load Tests on Piles: This test will be carried out as stipulated in IS-2911
(Part IV) 1995.

48. PILE LOAD TEST
 Lateral Load Tests on Piles
• The jack should be placed horizontally, between two piles.
• The load on the jack shall be the same on both the piles.
• The load will be applied in increments of 20% of the estimated safe load and at the
cut off level.
• The load will be increased after the rate of displacement is nearer to 0.1 mm per 30
minutes.
• If the cut-off level is approachable, one dial gauge exactly at the cut-off level shall
measure the displacement.

49. PILE LOAD TEST
 In case the cut-off level is not approachable, 2 dial gauges 30 cm apart vertically,
shall be set up and the lateral displacement of the cut-off level calculated by similar
triangles.
 The safe load on the pile shall be the least of the following:-
a) 50% of the final load at which the total displacement increases to 12 mm.
b) Final load at which the total displacement corresponds to 5 mm.

50. PILE LOAD TEST
 Pull out Tests on Piles:-
• A suitable set up shall be designed to provide an uplift force to the piles.
• The load increments and the consequent displacements shall be as per the case of
a vertical load test.

51. PILE LOAD TEST
 The safe load shall be the least of the following:
a) 2/3rd of the load at which the total displacement is 12 mm or the load
corresponding to a specified permissible lift.
b) Half of the load at which the load displacement curve shows a clear break.

52. PILE GROUPS
 Piles are generally used in groups with a common pile cap. A group may consist of two or three, or as
many as ten to twelve piles depending on the design requirement.
 The load carrying capacity of a group of piles is given by
(Eq. 6)

53. PILE GROUP EFFICIENCY
 Its value for bearing or friction piles at sites where the soil strength increases with depth is
found to be 1.
 For friction piles in soft clays the value on n is less than 1. The actual value of n depends on
soil type, method of pile installation, and pile spacing.
 When piles are driven in loose, sandy soils, the soil is densified during driving, and n >1 in
such cases.
 It has been observed that if the spacing between piles is more than 2.5 times the pile diameter,
the group efficiency is not reduced.
 The large pile to pile spacing will increase the overall cost of construction. The reduction in
load capacity due to the group effect can be estimated empirically.

54. ULTIMATE LOAD CARRYING CAPACITY FOR THE PILE GROUP
 The ultimate load carrying capacity for the pile group taken as a block is given by

55. EFFICIENCY OF PILE GROUP
 Efficiency of a pile group is given by
 n= Ultimate bearing capacity of pile group .
n X ultimate bearing capacity of single pile in group
 whre n = no. of piles in a group

56. Group effect of Piles

57. SETTLEMENT OF PILE GROUPS
 Due to group action , both immediate and consolidation settlement values of a pile group are
greater than those for a single pile.
 For bearing piles the total foundation load is assumed to act at the base of the piles on an
imaginary foundation of the same size as the plan of the pile group.
 For friction piles it is virtually impossible to determine the level at which the structural load is
effectively transferred to the soil. The level used in design is at a depth of two-thirds the
penetration depth.

58. NEGATIVE SKIN FRICTION
 Negative skin friction is a downward shear drag acting on the pile surface due to relative downward
movement of soil strata surrounding the pile.
 The following are some of the causes of negative skin friction
• Due to pile or pile segment passing through compressible soil stratum which consolidates
• Due to placement of a fill on compressible soil layer causing the layer to consolidate
• Lowering of ground water table causing the shrinkage of expansive soils.
• Under consolidated natural or compacted soils.
• The negative skin friction of a single pile is given by
Negative skin friction load = Unit frictional resistance (downward)* Length of the pile above bottom of
the compressible layer * Perimeter of the pile cross section
And total downward load= negative skin friction load + live load+ dead load

59. REFERENCES
 Foundation Engineering; PHP Publications
 Craig's Soil Mechanics
 Basic & Applied Soil Mechanis; A S R Rao
 Module 5 Deep Foundations; nptl
 Pile Foundation; Varanasi Rama Rao, Engineer- Civil & Structure

60. THANK YOU..!!