Underpinning

Foundation Engineering

Underpinning of Foundations

`

2



Fields of Application

Introduction

Installation Methods

Design of Underpinning

Iftikhar 05-CE-62

General Steps For Underpinning

Introduction

• Underpinning is a term applied to a group of methods used for constructing new foundation under existing structure.

`

3




Introduction



Iftikhar 05-CE-62


`

4




Introduction



Iftikhar 05-CE-62



Underpinning is required in those cases,– When a building is constructed

below the foundation level of an adjacent structure.

– Industrial buildings which are reconstructed to accommodate heavier and larger machinery.

`

5




Introduction



Iftikhar 05-CE-62



Some other cases are,– Construction of shallow subway lines

built in congested cities centers under existing buildings.

– Conservation of old buildings and monumental structures.

`

6




Introduction



Iftikhar 05-CE-62



• Still more,– A basement is built inside a building.– The settlement of a structure with

poor foundations is to be prevented.– Moving of structures from one side

to another represents another field of application of these methods.

`

7




Introduction



Iftikhar 05-CE-62



• Following are the major steps that are to be followed in any type of underpinning operation,

• Feasibility.

• Setting out.

• Excavation & Shoring.

• Concreting.

• Backfilling.

`

8




Introduction



Iftikhar 05-CE-62


Feasibility

• Before underpinning is commenced, an investigation should be carried out by an experienced and competent person.

• It is to determine whether an underpinning procedure will achieve the object intended.

`

9




Introduction



Iftikhar 05-CE-62


Setting Out

• The foundation portion that has to be underpinned is marked very carefully at every 1m in case of wall and less in case of column.

`

10




Introduction



Iftikhar 05-CE-62


Excavation and Shoring

• The ground is excavated equally on both sides of footing up to the required depth.

• The portion to be underpinned is shored against lateral movement by means of preliminary supports.

`

11




Introduction



Iftikhar 05-CE-62


`

12




Introduction



Iftikhar 05-CE-62


Concreting

• Place the concrete to a depth of 75mm below the existing footing and vibrate.

• After not less than 24 hours curing, dry pack the void with 1:3 cement, sharp sand mixed with a minimal amount of water and well rammed into place.

• Allow a further 24 hours before excavating adjacent to a mass filled or dry packed underpinned section.

`

13




Introduction



Iftikhar 05-CE-62


Mass Fill Method

Dry Pack Method

`

14




Introduction



Iftikhar 05-CE-62


Back Filling

• All excavations for working width not concreted should be backfilled with clean stone, compacted in max 200mm thick layers.

`

15




Introduction



Iftikhar 05-CE-62



• Underpinning is usually applied to buildings whose cost is higher than the cost of existing structure.

• Exception to this rule are structures which have service or memorial.

`

16




Introduction



Iftikhar 05-CE-62



• Analysis of underpinning starts with the evaluation of the loads acting on the foundations.

• Bearing capacity of the existing foundations is determined and the strength of the structure to be underpinned is assessed.

`

17




Introduction



Iftikhar 05-CE-62



• The underpinning should be about 0.3 to 0.5-m deeper than the level of the excavation, and it should carry the load all the way to the stratum in which the permissible settlement is ensured.

`

18




Introduction



Iftikhar 05-CE-62



• Underpinning is a tedious work which must be done very carefully in order that the structure to be underpinned should not be damaged.

• Before underpinning is undertaken the existing foundation should be uncovered.

• Underpinning is a slow and expensive work, underpinning generally takes several months.

`

19




Introduction



Iftikhar 05-CE-62



• It is a highly expensive work and requires specialized kind of work force so proper attention should be given to it.

• Different installation methods are given in the coming slides.


Underpinning Methods

21



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods

Underpinning of Columns

Akash Shahzad Khan 05-CE-42

Underpinning Methods

The numerous foundation methods employed in underpinning, classified according to the elements used in the process,

• Pit Piers

• Jacked Piles

• Root Piles

• Special Methods

All these methods produce, under structure, a support to which the load is transferred.

22



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



Pit Piers

• For underpinning of wall footing.

• Using access pits (B<2m) alongside the wall to be underpinned.

• Afer excavating the pit 1.8m deep under the bottom of footing it is cut in horizontally under the wall like lateral adit.

23



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



7-10

cm

Dry

packing

Wedge

Access Pit

Preliminary Supports

Lateral AditsAbout 2m

24



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



Pit Piers

• Masonry piers of hard burnt bricks or precast concrete blocks are built up using cement mortar and 5mm thin joint.

• The spacing of the successive pits is kept greater than 4m to ensure ground of sufficient bearing capacity to carry the load.

25



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



Pit Piers

• Dry packing (7-10cm thick) is used to transfer the load so that the building does not settle.

• It consists of thoroughly rammed stiff cement mortor, hard wooden pieces and rammed roof tiles.

• If the walls are not strong enough preliminary supports are installed before starting underpinning.

26



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



27



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



7-10

cm

Dry

packing

Wedge

Access Pit

Preliminary Supports

Lateral AditsAbout 2m

28



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



29



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



Jacked Piles

• Jacked piles are used for underpinning in water bearing soils.

• By this technique a spread footing is converted into pile footing.

• Its reliability is increased due to the fact that precise control can be exercised while load is being taken up by the piles.

30



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



31



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



Root Piles• They are used in the conditions

when the spaces for underpinning and headroom is restricted.

• Thought of less bearing capacity(150-600kN) it may prove economical.

32



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



Root Piles

• They can be drilled from both sides of walls forming an A-frame.

• When the wall is accessible from one side they may be installed in a fan-like manner.

• They are also used for underpinning bridge piers and retaining walls.

33



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



Root Piles

• Their key advantage lies in the fact that they are installed just from the ground level requiring no access pits and is not affected by water bearing soil.

34



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



High Bearing Capacity Soil

Basement Floor Level

Sidewalk Level

35



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



High Bearing

Capacity Soil

Bridge Pier

36



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



Ground Level

Retaining Wall

Rock or Hard Strata

37



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



38



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



Special MethodsGrouting

• Used for building situated above subway lines.

• Grouted arch is provided so as to prevent the settlement.

• It may also be used in place of pit piers in order to utilize full advantage of large area.

• However, it is rarely used due to is instability in some cases and because of economic reasons.

39



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



Special Methods

Ground Freezing• It is even less common.• It may be used as temporary work

with later permanent solution.

40



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods




• Columns bearing on square or rectangular footing can be underpinned by using pit piers.

• Preliminary supports are needed in this case.

• Driven piles are not recommended due to the detrimental effects of vibration on the structure.

41



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



42



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



43



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



44



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods



45



Pit Piers

Jacked Piles

Root Piles

Underpinning

Methods

Special Methods




05-CE-44 Akmal

Lateral Underpinning

47



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

Lateral Underpinning

• In lateral underpinning a wall is used to prevent the subsoil from spreading laterally, thus eliminating the settlement.

48



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

Types of Lateral Underpinning

• The following four kinds of walls are used in lateral underpinning:

• Soldier pile walls.• Sheet pile walls.• Pier walls.• Diaphragm walls.

49



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

Soldier Pile Walls• These walls are suitable for dry

dense soils.

• Example is the installation of Soldier pile wall around the perimeter of old building for the purpose of enclosing the land cofferdam.

• The soldier piles are driven in the ground and tied back by in-situ anchoring.

50



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

Soldier Pile Walls

• The effect of vibration caused by driving is negligible, Process is however noisy.

• The tie-back walls do not prevent the movement of a wall for a long period, especially when applied in clay soils.

• Soldier piles cannot be used in water bearing soils.

51



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

52



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

53



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

54



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

Sheet Pile Walls

• These can be used in water bearing soils.

• Its installation is noisy process. That is why these are seldom used in city centers.

• They only appear in the underpinning of industrial buildings.

55



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

56



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

57



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

58



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

59



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

60



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

Pier Walls• They are used in dry soils where pit

piers constructed under the footings can be replaced by drilled walls installed along the footings.

• They behave better statically than the diaphragm walls, as they ensure a short undercut length of footing to be underpinned.

61



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

Pier Walls

• Pier walls are economically competitive with diaphragm walls.

• They are installed by means of drilling which ensures less noise.

62



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

63



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

64



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

65



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

Diaphragm Walls• In water bearing soils, these walls

are economically acceptable if they double for permanent walls as well as serving in underpinning.

• These are used when diaphragm sections are longer than 6 m & loads applied by footings of adjacent footings are more than 300 kN & soil is not too permeable.

66



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

Diaphragm Walls

• Both diaphragm & drilled pier walls have an advantage over steel sheeting & soldier pile walls that they are appreciably stiffer & their deflection is therefore small.

67



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

68



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

69



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

70



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

71



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

72



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

73



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

74



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

75



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

76



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

77



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44

78



Soldier Pile Walls

Sheet Pile Walls

Pier Walls

Lateral

Underpinning

Diaphragm Walls

Ch. Akmal 05-CE-44


Bridging Supports

80



Geological Conditions

Bridging Supports

Difficulties Encountered

Installation of Supports

Necessity of Bridging

Faheem Rasool 05-CE-52

Bridging Supports

• Bridging supports are structures used for the underpinning of buildings which are situated above the cuts of shallow sub way lines.

• They consist of bridging beams supported by pit piers.

81




Bridging Supports






• The bridging supports are frequently needed in cities having streets which are not wide enough to accommodate the tubes or the stations.

• The structures lying above the curved tracks which cannot follow the contour of the street corners must also bear on bridging supports.

82




Bridging Supports





Installation Of Supports

• The installation of Bridging supports involve difficult and expensive operations of eccentric underpinning which is carried out in several stages and thus considerably impedes the progress of work.

• Due to this costly undertaking sometimes the grade line brought down to a depth at which no underpinning was required.

83




Bridging Supports






• Underpinning is a process to enhance the properties of foundations. Sometimes existing foundations as discussed in previous slides.

• Geological conditions are favorable in hard strata.

84




Bridging Supports






• The difficulties encountered in the underpinning of buildings situated above the subway lines lie in the fact that the underpinning construction cannot be placed under walls where it interfere with the track.

• The bridging beams which must be placed beneath the underpinned footings, usually bear on pit piers located outside the tunnel.

85




Bridging Supports






• The transfer of the footing load is accomplished by prestressing.

• Simple or cantilever steel beams are preferred in the construction of bridging supports.


Enlarging Of Foundation

87




Bridging Supports





Enlarging of foundation

• Enlarging of foundation is employed whenever the groundwater level is close to footing and the pit pier and jacking methods are hardly to apply.

• Enlarging by continuous footing of concrete is feasible when foundation soil has high bearing capacity.

88




Bridging Supports





Enlarging of foundation

• When soil has low bearing capacity, enlarging must be supported by piles.

• Enlarging of square or rectangular footings can be effected by means of buttressed collars.

• The method of underpinning by means of root piles make possible to install root piles water bearing soils down to firm supporting stratum.

89




Bridging Supports





Enlarging of Continuous Footing

It is carried out in two stages:• One side of footing is enlarged first ,the

other side afterwards without recourse to preliminary supports.

• The first step of enlarging operation consists of inserting needle beams in holes drilled through the wall.

• The needle beams which are I-sections are prestressed against the walls by means of a dry pack and against the enlargements by means of wedges.

90




Bridging Supports






91




Bridging Supports






92




Bridging Supports






• After the prestressing they are encased in concrete.

• The wedges must produce a deflection of needle beams corresponding to the load P applied by wall.

• The needle beams transmit the load to enlargements,where reaction A1 and A2 acts.

93




Bridging Supports






• The existing footing is thus relieved from load and the width of footing bottom which transmit the load is only equal to B1+B2.

• The enlargements are cantilevered below the old footing and this arrangement reduces the overall width of enlarged footing.

94




Bridging Supports





Square & Rectangular Footing

• This type of footing can be enlarged by means of encasing buttresses.

• This method has successfully been applied to underpinning of building columns, towers, underscoured bridge piers etc

95




Bridging Supports






96




Bridging Supports






• It employs buttress collars consrtucted around the structure.

• Since the collars can be cast to a considerable height,the area of contact between the old and new masonry or concrete is sufficient to transmit the load to enlargement,provided that chases are cut in old face.

97




Bridging Supports






The roughened face should be clean,for surface dirt is capable of breaking the bond.

The concrete collar cast around the footing shrinks the ensuing pressure compresses the footing.

The collars must be heavily reinforced.

98




Bridging Supports






Moving Of Structures

100



Moving of Structures

Aleem Daar 05-CE-60

Operational Steps

Horizontal & Vertical Moving

Procedure for Moving Structures

Global Examples

Operational Steps• Structures can essentially be moved

vertically, horizontally, or in both directions. The operation consists of the following steps,– Underpinning of the walls and columns

above the foundation.– Cutting the structure across in a

horizontal plane to separate it from the footings.

– transferring the load to a vehicle and moving.

101




Aleem Daar 05-CE-60

Operational Steps



Global Examples

Vertical & Horizontal Moving

• Vertical moving is necessary in those cases when the clearance of a flyover is required to be raised.

• Horizontal moving of structures is sometimes used when streets are to be widened or industrial buildings relocated.

102




Aleem Daar 05-CE-60

Operational Steps



Global Examples

Vertical & Horizontal Moving

• Railways bridges, blast furnaces etc, erected alongside old operating units are moved horizontally when a speedy replacement of the old unit by a new one is essential.

• Moving is also applied to landmarks and monuments lying.

103




Aleem Daar 05-CE-60

Operational Steps



Global Examples

Transfer of Weight

104




Aleem Daar 05-CE-60

Operational Steps



Global Examples

Elevation & Plan of Track

105




Aleem Daar 05-CE-60

Operational Steps



Global Examples

Procedure of Moving Structures

• The weight of the structure is transferred to steel stringers beams encased in concrete in chases cut in the masonry.

• The stringer beams bear on needle beams which enable the structure to be move on rails ,usually with gradient of 0.1% in the direction of moving.

106




Aleem Daar 05-CE-60

Operational Steps



Global Examples


• The rails are laid on strong ties which are in turn supported by longitudinal beams resting on a high capacity bearing soil or piles.

• A rigid track is advantageous for small moving distances, while rigid underpinning is preferred for long distances.

107




Aleem Daar 05-CE-60

Operational Steps



Global Examples


• Once the underpinning operation is completed ,the structure is separated from the footing and moved by means of horizontal hydraulic jacks applying a force of about 1 to 2% of its weight.

108




Aleem Daar 05-CE-60

Operational Steps



Global Examples

Precaution

• The structure to be moved should be heavily shored both outside and inside and tied and braced to prevent it from being damaged during the moving operation.

109




Aleem Daar 05-CE-60

Operational Steps



Global Examples

Global Examples

• One of most spectacular examples of moving ever performed was 60m vertical rising of Abu Simbul Temple.

• The great temple weighed 2,500,000 KN and the small temple 1,500,000 KN.

110




Aleem Daar 05-CE-60

Operational Steps



Global Examples

Global Examples

• California Palace of the Legion of Honor, San Francisco, California

111




Aleem Daar 05-CE-60

Operational Steps



Global Examples

Global Examples

• The moving of Amada temple weighing 8,000 KN in one piece on an incline to a height of 65 m and a distance of 2600m.

• Eighteen Egyptian temples were moved to save them form being flooded along Nile above Aswan Dam.

112




Aleem Daar 05-CE-60

Operational Steps



Global Examples

Global Examples

• Another notable engineering achievement was the moving of church of the Virgin Mary in Czechoslovakia, realized in 646 hours of travel ,in october 1975.

• The church was underpinned by a grid of reinforced concrete beams.

113




Aleem Daar 05-CE-60

Operational Steps



Global Examples

Examples

• The working drawing of an underpinning project will be shown in next slides.

114

115

Date post:	22-Dec-2015
Category:	Documents
Upload:	kkhalid-yousaf
View:	7 times
Download:	1 times

Underpinning

Documents