bulding foundation for costruction (6).ppt

3
Construction activities/stages
Site preparation Sub-structure Super
structure
External work
Site clearing Foundation Building frame roads
earthwork Piling works Upper floors parking
hoarding Under-Ground floor walls drains
Temporary roads Ground beam roofs fencing
Temporary
buildings
Hard core, d.p.c Windows,
doors
turfing
Finishes,
facilities

4
SUBSTRUCTURE
A man-made structure that is
needed to hold the
superstructure in place and to
transmit all forces due to the
superstructure and its use to
whatever the supporting material
may be

6
SUBSTRUCTURE’S
ELEMENT
 Foundation
 Underground Floor
 Ground Beam

7
FOUNDATION
Is the base on which a building rests
and its purpose is to safely
transfer the load of a building to a
suitable subsoil.

8
The Building Regulations require all
foundations of buildings to:
 Safely sustain and transmit to the ground the combined
dead and imposed load so as not to cause any settlement
or other movement in any part of the building or any
adjoining buildings or works.
 Be of such a depth, or be so constructed, as to avoid
damage by swelling, shrinkage of the subsoil.
 Be capable of resisting attack by deleterious materials, such
as sulphates, in the subsoil.
Subsoil – soils below the topsoil; the topsoil being about 300mm deep.

9
Typical subsoil bearing capacities
Types Bearing capacities
(KN/m2)
Rocks, granites and chalks 600 – 10,000
Non-cohesive soils, compact
sands;loose uniform sand
100 - 600
Cohesive soil, hard clays, soft clays
and silts
< 600
Peats and made ground To be determined by investigation

10
Terminology
 Backfill – materials excavated from site and if suitable
used to fill in around the walls and foundations.
 Bearing capacity – safe load per unit area which the
ground can carry.
 Bearing pressure – the pressure produced on the ground
by the loads.
 Made ground – refuse, excavated rock or soil deposited
for the purpose of filling in a depression or for raising the
site above its natural level

11
Terminology (cont’d)
 Settlement – ground movement which may
caused by:
-deformation of the soil due to the imposed load.
-volume changes of the soil as a result of seasonal
conditions
-mass movement of the ground in unstable areas.

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FUNCTIONS OF
FOUNDATION
 To transfering loads
 To avoid settlement

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FACTOR AFFECTING
THE DESIGN OF
FOUNDATION
 Loading
 Soil
Condition
 Cost
 Technology

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Loading
 Imposed load
 Dead load
 Wind

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Soil condition
 Bearing capacity
 Ground water level
 Chemical attack

16
Cost
 Material
 equipments

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Technology
 Expertise
 Skilled workers

18
Choice of foundation type
 The choice and design of foundations for
domestic and small types of buildings depends
mainly on two factors:
1. the total loads of the building.
2. the nature and bearing capacity of the subsoil.

19
 The total load of a building are taken per metre
run and calculated for the worst case.
 The nature and bearing capacity of the subsoil
can be determined by:
-trial holes and subsequent investigations
-bore holes and core analysis
-local knowledge

20
TYPES OF FOUNDATIONS
1. Shallow Foundation
2. Deep Foundation

21
SHALLOW FOUNDATION
Shallow foundation - when the foundation depth are less then their
structure width
Those which transfer the loads to
subsoil at a point near to the ground
floor of the building.

22
DEEP FOUNDATION
Deep foundations - when the foundation depth is exceeding their
structure width
Those which transfer the loads to a subsoil some
distance below the ground floor of the building.

23
SHALLOW
FOUNDATION
 Isolated/Pad
Foundation
 Raft/Mat Foundation
 Strip Foundation

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DEEP FOUNDATION
 Pile Foundation

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PAD FOUNDATION
A pad used to “spread out”
building column and wall
loads over a sufficiently
large soil area

27
What is Pad Foundation?
Also known as Pad
Base.
The simplest
foundation for a
column in a steel or
reinforced concrete
framed building.

30
Steps in pad foundation
 Setting out
 Excavation
 Material preparation –reinforcement,
formwork, cement, aggregates
 Formwork construction
 Reinforcement
 Concrete work –mix, placement,
treatment, compaction, testing

31
Main Types of Pad Foundation
Two main types are common:
Mass Concrete
Reinforced Concrete

32
Mass Concrete
Most economic.
Most commonly used in construction
site.
Simply excavate and pour concrete.
Simple 45o
spread of load from
column to soil formation.

34
Reinforced Concrete
Avoid reinforcing a base if possible.
Very expensive due to extra preparation.
Intensive inspection is required.
Excavation is open longer.

35
More operations:
Excavate – shutter – pour blinding – fix
reinforcement – inspect – pour concrete
However, the reinforcement allows the
base to behave like a cantilever slab.
Reinforced Concrete (C’td)

36
How To Choose???
Mass Concrete Bases:
Reinforced Concrete Bases:
Use wherever possible.
Unstable excavation.
Quick, economic construction.
High water table.
Adverse changes in soil strata
Thin soil strata.
Buried services/ structures.
Underground obstructions.

37
RAFT FOUNDATION
 Is to spread the load over the entire area
of the site.
 This method is particularly useful where
the column loads are heavy and thus
requiring large bases or where the
bearing capacity is low, again resulting in
the need for large bases.

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RAFT FOUNDATION
Solid Slab Rafts
Beam and Slab Rafts
Cellular Rafts
3 types of Mat Foundation:

40
SOLID SLAB RAFTS
 Are constructed of a uniform thickness over the whole raft
area, which can be wasteful since the design must be based
on the situation where the heaviest load occurs.
 The effect of the load from columns and the ground
pressure is to create areas of tension under the columns
and the areas of tension in the upper part of the raft
between the column.
 Very often a nominal mesh of reinforcement is provided in
the faces where tension does not occur to control shrinkage
cracking of the concrete.

42
Beam and slab rafts
 As an alternative to the solid slab raft and are used where
poor soils are encountered.
 The beams are used to distribute the column loads over the
area of the raft, which usually results in a reduction of the
slab thickness.
 The beams can be upstand or downstand depending upon
the bearing capacity of the soil near the surface.
 Downstand beams will give a saving on excavation costs
whereas upstand beams create a usable void below the
ground floor if a suspended slab is used.

44
Cellular rafts
 Can be used where a reasonable bearing capacity
subsoil can only be found at depths where beams
and slab techniques become uneconomic.
 The construction is similar to reinforcement
basement except that the internal walls are used
to spread the load over the raft and divide the
void into cells.
 Openings can be formed in the cell walls allowing
the voids to be utilised for the housing of
services, store rooms or general accommodation.

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STRIP FOUNDATION
Loads are transmit
through wall

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 Are used to support and transmit the loads from heavy walls.
 The effect of the wall on the relatively thin foundation is to
act as a point load and the resultant ground pressure will
induce tension on the underside across the width of the strip.
 Tensile reinforcement is therefore required in the lower face
of the strip with distribution bars in the second layer running
longitudinally.
 The reinforcement will also assist the strip in spanning any
weak pockets of soil encountered in the excavation

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STRIP FOUNDATION
 Ordinary Strip Foundation
 Wide Strip Foundation
 Deep Strip Foundation

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 Use for single/double storey building
 Good bearing capacity & no shrinkage

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 Low bearing capacity
 Use reinforcement, concrete 1:2:4

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Deep Strip Foundation
-Clayey soil
-The width of the strip footing greater than width of the
wall
-1:3:6

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Construction process
 Same as pad foundation
 Design is different
 Starting with excavation - backhoe
 No formwork is needed
 After excavation is completed, pour the
concrete (must have good workability)

56
Column inserted in the
ground to transmit the
structural loads to a lower
level of subsoil
PILE FOUNDATION

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• When bearing strata level is more than 3
meters deep
• Load of building are not uniform
• The live load and dead load coming from
the structure considerably large
• The construction of raft foundation is
economical and the seasonal variation of
ground water level is considerable
Why we use pile ?

58
Piles are classified by :
• The material of which they are formed
• By their manner of installation.
Classification of piles
There are :
• Replacement pile (also known as
bored pile or end bearing)
• Displacement pile (also known
as friction pile or driven pile)

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Driven pile Bored pile
PILE
Cast In-situ Pre-cast Semi-pre-cast
Concrete Steel Timber
Concrete and timber Concrete and steel
Rotary Flush Percussion
Concrete

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Piles which are driven, thus displacing the soil and includes
those piles which are perform, partially perform or are driven
in-situ pile
M
A
T
E
R
I
A
L
S
•Timberpile
•Pre-castconcrete
•Sand
•Steel
•Wroughtiron
•Castironand
•Composite
Displacement piles

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Timber pile
• Trees are used as pile after removing
the bark and cutting of branches
• Most timber piles are fitted with an iron
or steel-driving shoe and have an iron
ring around the head to prevent
splitting due to impact
• The timber piles must be well season
and properly treated

62
• Cut easily
• Quickly driven into the ground
• More cheaper than most of materials
• Skilled supervision is not essential
• Not capable of taking heavy load
• Difficult to drive the pile into hard strata
• A joint in longer pile is a weak spot
• They deteriorate by the action of water,
soil, insect etc
Advantages
Disadvantages

63
Pre-cast concrete pile
Advantages
 The reinforcement is maintained in the correct
position
 The best quality of concrete can be produced
 The proper curing is done
 These piles can be driven under water
 Defects of casting may be examined and repaired
before driving the pile
 Such types of piles have high resistance to
biological and chemical actions of the ground
• Square section with chamfered corner, octagonal, or
round section
• Shoes are provided at the lower end

64
Disadvantages
 These piles are very heavy and difficult to transport
 The shocks and vibrations render them weaker
 Extra reinforcement is essential to take care of
handling and driving stresses
 A weak joint is formed in case of lapping additional
length
 Progress of work at the site may go delayed due to
inadequate supply of piles at short notices
 If proper care is not taken, the piles may be damaged
during transportation and driving

65
Pile Driving
• Piles is driven into the ground by holding them in the
correct position against the piling frame and applying
hammer blows to the head of the piles
• Pile hammers come in a variety of type and sizes
powered by gravity, steam, compressed air or diesel
Drop hammers
• Single acting hammer - use steam or air pressure to
raise the ram
• Double acting hammer - the double acting utilizes steam or
air pressure to power both the up and down strokes
of the hammer ram
Threetypes of driving piles that are commonlyuse :

66
Diesel hammer
Internal combustion hammer, which utilizes
the explosion of the diesel fuel between
the bottom of ram and the anvil block
Vibratory driver
Cause penetration of the pile into the soil
by exciting the pile with either non-
resonant or resonant longitudinal
vibration

67
Replacement pile
 Formed by removing a column of soil and
replacing with in-situ concrete or as in the
case of composite piles with pre-cast and in-
situ concrete
There are three typesof replacement :
• Precussion bored piles
• Rotary bored piles
• Prestcore piles

68
Bored Piles
 Bored cast-in-place piles
 Grout or concrete intruded piles

69
Bored Cast-in-Place Piles
 Small-diameter percussion bored cast-in-
place piles
 Large-diameter percussion bored piles
 Rotary bored cast-in-place piles

70
Small-diameter percussion
bored cast-in-place piles
 Minimum pile diameter = 300mm
 Maximum pile diameter = 600mm
 Boreholes formed by rigs used in site
investigation.
 Cohesive soil – Clay Cutter
 Granular soil – shell

71
Tripod rig for drilling boreholes

72
Tripod rigs are light, easily transported,
low headroom required.

73
Typical cutting tool used in small diameter

74
Actual cutting tool used in construction

75
Shell for small-diameter
percussion bored piles

76
Large-diameter percussion
 Size of boreholes with diameter 600mm or
more.
 well suited to the penetration of hard
strata, which may include weak
sedimentary rock
 Uses semi-rotary down-hole percussive
hammer rigs.
 Example : Libore rig by Lilley Construction

78
Rotary bored cast-in place
piles
 Large boreholes from 750mm up to 3m
diameter are possible by using rotary
drilling machinery
 A spiral or bucket auger is attached to a
shaft known as a Kelly bar
 Depths of up to 70m

79
 In soft silts and clays, bentonite slurry
is used
 Potential for under reaming
 Underreaming – Technique to enlarge
the base of bored pile to increase the
bearing capacity.

80
Boring tools used in the construction of
rotary bored cast-in-place piles

81
Underreaming
tool in the
closed position

82
Underreaming
tool in the open
or working
positon

83
Continuous-flight augered piles
 Becoming a popular method in pile
construction
 Offer considerable environmental
advantages
 noise and vibration levels are low
 No need for temporary borehole wall
casing or bentonite slurry

84
 Process of construction:
- Screwing the continuous flight auger
into
the ground to the required depth
leaving
the soil in the auger
- Grout (or concrete) can then be
forced
down the hollow shaft of the auger

85
 The auger is lifted out of the ground as
the grout continues to be intruded
 Reinforcement can then be lowered in
before the grout sets

86
Continuous-flight
augered piles with
grout intrusion

87
Step 1
1.1. Set out the positions of the bored piles as per construction drawing.
2.2. Mark the pile positions with pegs.
3.3. Survey the existing ground level at the pile position.
Installation of Bored Pile

88
Step 2
1.1. Mobilize the boring plant to the intended bored pile position.
2.2. Position the centre of the auger exactly above the pile point.
3.3. Check the verticality of the kelly bar before boring commences.
4.4. Offset two reference point perpendicular to each other from the pile position.

89
Step 3
1.1. Commence boring at the pile position.
2.2. Check the verticality of drilled hole during boring works.

90
Step 4
1.1. Observe the stability of borehole during boring works.
2. If the borehole is unstable or collapsible, insert a temporary casing into the borehole.
3. Check the verticality of the temporary casing during installing. Use two plumbs
positioned in perpendicular directions to each other.

91
Step 5
1. Continue boring with an auger or boring bucket depending on the soil condition
as
shown in (a) and (b) next page.
2. Carry out boring until the designed depth is achieved.
3. If hard material is encountered during boring, use chisel or rock tools to
penetrate
into the hard stratum as shown in (c) next two page.

94
Step 8
1. After reaching to the required depth, clean the base of the borehole with a cleaning bucket.
2. Verify and confirm the length with client's representative.

95
Step 9
1.Check and ensure the reinforcement and dimensions of the cage are appropriate
for the intended pile. Ensure that the cage is intact for handling.
2.Hoist and transfer the pre fabricated reinforcement cage from the reinforcement
yard to the borehole.
3.Lower the reinforcement cage into the borehole to the cut off level.
4.Ensure that the cage is maintained at the cut off level during concreting works.

96
Step 10
Concreting in dry hole conditions
1.Discharge concrete directly from the concrete truck into the hopper.
2.When concrete has reached above the cut off level, stop concrete works.
3.Ensure that sound concrete has reached above the cut off level.

97
Step 11
Concreting in dry hole conditions

98
Step 12
Concreting in wet hole conditions by tremie method
1.1. Insert the concrete plug at the bottom of tremie pipe hole.
2.2. Lower the tremie pipe to the toe of borehole.
3.3. Discharge concrete directly from the concrete truck into the hopper.
4.4. Fill concrete from the bottom of borehole which displaces the sludge as concrete rises to the top.

99
Step 13
Concreting in wet hole conditions by tremie method
1. Withdraw the tremie pipe as concrete rises upwards.
2. Ensure that the end of tremie pipe is embedded into the concrete at all times during concreting works.
3. When concrete has reached above the cut off level, the tremie pipe is withdrawn completely.
4. Ensure that sound concrete has reached above the cut off level.

100
Step 14
1. Extract the temporary casing from the borehole upon completion of concreting works.
2. Ensure that the temporary casing is extracted vertically.

101
Bored Cast-in-situ Piles - Special
techniques to improve Bearing Capacity
Underreaming - When
employing the rotary
excavation method, an
enlarged base
(underream), also known
as bell, can be created,
which increases the base
bearing capacity of piles
in competent soil strata.

102
Advantages of Bored Piles
Length can be readily varied to suit varying ground conditions
Can be installed in very large diameters
End enlargements up to two or three diameters are possible in clays
Material of pile is not dependent on handling or driving conditions
Can be installed in very long lengths
Can be installed without appreciable noise or vibration
Can be installed in conditions of very low head-room
No risk of ground heave

103
Disadvantages of Bored Piles
Susceptible to "waisting" or "necking" in "squeezing"
ground.
Concrete is not placed under ideal conditions and
cannot be subsequently inspected.
Enlarged ends cannot be formed in cohesionless
materials.
Cannot be readily extended above ground level
especially in river and marine structures.

104
Precussion Bored Piles
 Suitable for small and medium-sized contracts of up
to 300 piles in both either clay or gravel subsoil
 The steel lining tube usually sink under its own
weight but it also can driven by using slight pressure
for example hydraulic jacks
 Usually compressed air is use to tamp and
considerate the concrete but we can also use internal
drop hammer
 Figure
Back

105
Rotary Bored Piles
 Large diameter piles are bored using rotary method
 The rotary bored piles are suitable for most cohesive
soils such as clay and are formed using auger
 Compaction of the concrete usually by a tremie pipe,
is generally by gravitational force
 Test loading of large-diameter bored piles can be very
expensive and it can render this method uneconomic
Back

106
Prestcore piles
 Formed of composite pile consisting of pre-cast in-situ concrete.
 Concreting in ‘dry’ bores
 Formation of a prestcore pile can be divided into four distinct stages :
1) Boring Lined borehole formed by percussion methods using
tripods rig
2) Assembly pre-cast units that form the core of the piles core
of the pile are assembled on
special mandrel and reinforcement is inserted before the
core unit is lowered into position
3) Pressing the core, raising and lowering the pile core by
means of a pneumatic winch attached to the head of the
lining tube to consolidate the bearing stratum
4) Grouting Withdrawal of the lining tube and grouting with the
aid of compressed air to expel any ground water

107
PILE GROUP
 A group of pile which act in the dual role of reinforcing the
soil, and also of carrying the applied load down to deeper,
stronger soil strata
 On the top of group piles, pile cap with reinforcement was
formed. The cap is form clear of the ground will be call a
freestanding group
PILE
COLUMN
PILE CAP

108
PILE TESTING
Loading test
The function of loading test are to :
a) Determine the load – settlement relationship
b) Serve as a proof test to ensure failure does not
occur and the value of the multiple is then
treated as a factor of safety
c) Determine the real ultimate bearing capacity

109
•MaintainedLoad Test
The procedure is to apply the load in stage being
maintained constant until the resulting settlement of the
pile substantially ceases before increasing the load to
the next higher stage
•ConstantRate Of Penetration Test
To understand the test it is helpful to regard the pile as a
device for testing the soil, and the piles movement as the
means of mobilizing the resisting forces
There are two test that commonly used :

110
Shoes for concrete piles
 Steel or cast-iron shoes with pointed or flat
ends
 Generally fitted to the concrete piles for
driving through coarse granular soils or
weak rock
 In uniform clays or sands, shoes are not
usually necessary
 Figure

111
Drive head
 Use to hold the head of timber, pre-cast
concrete, steel pipe or steel H-pile in
position under the hammer
 Distribute the hammer blow to the pile
head
 Also known as a drive cap, bonnet, hood,
helmet or follower

112
Pile caps
 Apart from the simple situations such as
domestic dwellings, or where large diameter
piles are employed
 To provide structural continuity - the
reinforcement in the piles is bonded into the pile
cap
 The head of piles also penetrate the base of the
pipe cap some 100 to 150 mm to ensure
continuity of the members
 Figure
Other picture

115
Piling equipment
Hammer
Shoe pile
Crane

117
Dynamic pile test
Driven pile
Finish

128
Problem in pile construction
 Driven pile
1. Design and manufacture
2. Installation of driven pile
3. Associated ground movements
4. Noise and ground vibration

129
 Bored pile
1. Excavation of the pile bored
-Over break
-Base of bored hole
-Effect of water in bored holes
2. Concreting the pile
-Quality of the concrete
-Placing concrete
-Extracting temporary casing
-Problem in soft ground
-Effect of ground water
2. Design of pile reinforcement
3. Piles constructed with the aid of drilling mud

130
Installation of driven piles
Damage to head of pre-cast
Buckling of steel H-pile
driven into boulder clay
Buckling of sheet steel piling

131
Over break
Bulbous projection on pile
shaft caused by over break

132
Base of bored hole
Blocks of clay fallen from under ream of
pile Toe of small-diameter pile
filled with silt prior to

133
Effect of water in bored holes
Toe of pile after concreting
with water in bore

134
Quality of the concrete
The effect of low slump concrete

135
Extracting temporary casing
Separation of pile
shaft caused by
extraction of casing
Defect in pile shaft
caused by water
The effect of a large
water-filled cavity
Defect caused by concrete
slumping into a dry cavity

136
Problem in soft ground
The consequent of ‘topping-up’
after extraction of casing
Waisting of a cast-in-place pile

137
Effect of ground water
Erosion of wet concrete by
groundwater flow : pile in fill

138
Design of pile reinforcement
Defects associated with
displacement of reinforcement

bulding foundation for costruction (6).ppt

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