CONSTRUCTION TECHNIQUES, EQUIPMENTS & PRACTICE

WelcomeWelcome

UNIT-3UNIT-3

SUB STRUCTURE SUB STRUCTURE CONSTRUCTIONCONSTRUCTION

1)1) Techniques of Techniques of a. Box Jackinga. Box Jacking b. Pipe Jackingb. Pipe Jacking

2)2) Underwater construction of Underwater construction of a. a. DiaphragmDiaphragm walls walls b. Basement b. Basement

3)3) Tunneling TechniquesTunneling Techniques

4)4) Piling TechniquesPiling Techniques

5)5) Driving wellDriving well

6)6) CaissonCaisson

7)7) Sinking CofferdamSinking Cofferdam

8) Cable Anchoring8) Cable Anchoring

9) Grouting9) Grouting

10) Driving Diaphragm Walls.10) Driving Diaphragm Walls. 11) Sheet Piles11) Sheet Piles

12) Shoring for deep cutting12) Shoring for deep cutting

13) Large reservoir construction with 13) Large reservoir construction with membranesmembranes

and earth system.and earth system. 14) Well Points14) Well Points

15) Dewatering and stand by plant equipment 15) Dewatering and stand by plant equipment forfor

underground open excavation.underground open excavation.

TECHNIQUES OF BOX JACKINGTECHNIQUES OF BOX JACKING

The need to install large structure without any disruption in congested The need to install large structure without any disruption in congested location.location.

Procedure:Procedure:

To insert timber into the subsoil by means of box andTo insert timber into the subsoil by means of box and excavate, as the driving proceeds.excavate, as the driving proceeds.

This method consists of driving of short timber runners, 1 to 2m long.This method consists of driving of short timber runners, 1 to 2m long. The process is repeated until the required depth has been reached.The process is repeated until the required depth has been reached. It is essential with all drive.It is essential with all drive.

In firm subsoil the shaft excavation would be carried out in stages of 1 to 2mIn firm subsoil the shaft excavation would be carried out in stages of 1 to 2m deep according to the ability of subsoil to remain stable for short periods.deep according to the ability of subsoil to remain stable for short periods.

Sometimes a series of cross beams are used at the head of shaft timbering, to Sometimes a series of cross beams are used at the head of shaft timbering, to reduce the risk of the shaft as excavation work is proceeding at the lower levels.reduce the risk of the shaft as excavation work is proceeding at the lower levels.

This method can be used for the installation of pipes from 150 to 3600mm This method can be used for the installation of pipes from 150 to 3600mm diameter but it is mainly employed on the larger diameter of over 1m.diameter but it is mainly employed on the larger diameter of over 1m.

PIPE JACKINGPIPE JACKING

Used for installation of pipes from 150 to 3600 mm diameter but onUsed for installation of pipes from 150 to 3600 mm diameter but on the larger diameters of over 1 m.the larger diameters of over 1 m.

Working:Working:

Force the pipes into the subsoil by means of a series of hydraulics jacks.Force the pipes into the subsoil by means of a series of hydraulics jacks.

Excavate as the driving proceeds, from within the pipes by hand or machine.Excavate as the driving proceeds, from within the pipes by hand or machine.

The leading pipe is usually fitted with a steel shield or hood to aid the The leading pipe is usually fitted with a steel shield or hood to aid the driving process.driving process.

This is a very safe method since the dangers of collapsing excavations are This is a very safe method since the dangers of collapsing excavations are eliminated.eliminated.

There is no disruption of surface.There is no disruption of surface.

Pipe jacking is suitable for driving pipe through an embankment to form a Pipe jacking is suitable for driving pipe through an embankment to form a pedestrian subway.pedestrian subway.

CLASSIFICATION OF PIPES BASED ON DIAMETER:CLASSIFICATION OF PIPES BASED ON DIAMETER:

i.i. Small pipes - 150 to 900 mm diameter .Small pipes - 150 to 900 mm diameter . ii.ii. Medium pipes - 900 to 1800 mm diameter. Medium pipes - 900 to 1800 mm diameter. iii.iii. Large pipes - 1800 to 3600 mm diameter. Large pipes - 1800 to 3600 mm diameter.

DIAPHRAGM WALLDIAPHRAGM WALL ““Diaphragm walls are underground structural Diaphragm walls are underground structural

elements commonly used for retention systems and elements commonly used for retention systems and permanent foundations walls.”permanent foundations walls.”

Used as a deep groundwater barriers Used as a deep groundwater barriers

Technique used:Technique used: “ “SLURRY TRENCH TECHNIQUE.” SLURRY TRENCH TECHNIQUE.”

Methods:Methods: Cast-in-place diaphragm wallsCast-in-place diaphragm walls

The precast diaphragm wallsThe precast diaphragm walls

CAST – IN – PLACE DIAPHRAGM CAST – IN – PLACE DIAPHRAGM WALLS:WALLS:

The trench is being excavated in The trench is being excavated in discontinuous sections or “panels”.discontinuous sections or “panels”.

Stop-end pipes are placed vertically at each end of the primary panel to form Stop-end pipes are placed vertically at each end of the primary panel to form joints for adjacent secondary panels.joints for adjacent secondary panels.

Then a steel reinforcement cage is placed in the centre of the panel.Then a steel reinforcement cage is placed in the centre of the panel.

Concrete is poured in one continuous operation through one or more tremie Concrete is poured in one continuous operation through one or more tremie pipes that extend to the bottom of the trench.pipes that extend to the bottom of the trench.

The tremie pipes are extracted as the concrete rises.The tremie pipes are extracted as the concrete rises.

The slurry that is displaced by the concrete is saved and for subsequent panel The slurry that is displaced by the concrete is saved and for subsequent panel excavations.excavations.

As the concrete sets, the end pipes are withdrawn.As the concrete sets, the end pipes are withdrawn.

The finished wall may be cantilever or require anchors or props for lateral The finished wall may be cantilever or require anchors or props for lateral support.support.

THE PRECAST DIAPHRAGM THE PRECAST DIAPHRAGM WALLWALL

A continuous trench or longer panelA continuous trench or longer panel is excavated under self-hardening is excavated under self-hardening cement –bentonite slurry.cement –bentonite slurry.

The slurry is retarded to remain fluid during construction.The slurry is retarded to remain fluid during construction.

After a sufficient length of excavation is complete, a crane lifts the After a sufficient length of excavation is complete, a crane lifts the precast wall section into the trench.precast wall section into the trench.

The cement bentonite slurry sets to form the final composite wall.The cement bentonite slurry sets to form the final composite wall.

Alternatively, the trench is excavated under bentonite slurry, which is Alternatively, the trench is excavated under bentonite slurry, which is then displaced with cement bentonite slurry.then displaced with cement bentonite slurry.

APPLICATIONS:APPLICATIONS: In congested areas.In congested areas. In close proximity to existing structures with minimal loss of support to existingIn close proximity to existing structures with minimal loss of support to existing foundations.foundations.

CONCLUSION:CONCLUSION: The diaphragm wall technique is a tried and true construction method, which The diaphragm wall technique is a tried and true construction method, which

provides unequal support of existing foundations during adjacent construction provides unequal support of existing foundations during adjacent construction operations.operations.

BASEMENTSBASEMENTS

““Basements are under ground structures that are linked to the Basements are under ground structures that are linked to the superstructure and functionally form an integral whole.”superstructure and functionally form an integral whole.”

Methods:Methods: Open excavation with sloped sides.Open excavation with sloped sides. Vertical cuts supported by temporary supports such as sheet piles or Vertical cuts supported by temporary supports such as sheet piles or

timber.timber. Vertical cuts supported by diaphragm walls, along with intermediate piles Vertical cuts supported by diaphragm walls, along with intermediate piles

& floor slabs which permit top-down construction.& floor slabs which permit top-down construction. Vertical cuts supported by diaphragm walls which become a part of the Vertical cuts supported by diaphragm walls which become a part of the

final basement structure.final basement structure. Prefabrication of the basement structure above the ground & sinking it Prefabrication of the basement structure above the ground & sinking it

into the soil.into the soil.

CAISSONSCAISSONS

““The caisson is a member with hollow portion, which after installing in The caisson is a member with hollow portion, which after installing in place by any means is filled with concrete or other material .”place by any means is filled with concrete or other material .”

It is preferred in sandy soils.It is preferred in sandy soils.

Purpose:Purpose: For placing a foundation in correct position under water.For placing a foundation in correct position under water.

Types of Caissons:Types of Caissons:

Open caissons or wells.Open caissons or wells.

Box caissons.Box caissons.

Pneumatic caissons.Pneumatic caissons.

OPEN CAISSON OR WELLS:OPEN CAISSON OR WELLS:

The caissons are open at both top and bottom.The caissons are open at both top and bottom.

They are used on sandy or soft bearing stratum.They are used on sandy or soft bearing stratum.

They are generally built of timber, metal, reinforced concrete or masonry.They are generally built of timber, metal, reinforced concrete or masonry.

They form the most common types of deep foundations for bridges in INDIA.They form the most common types of deep foundations for bridges in INDIA.

Shapes of WELLS:Shapes of WELLS:

CircularCircular

RectangularRectangular

Double-DDouble-D

Rectangular with D-shaped endsRectangular with D-shaped ends

Twin hexagonal and two octagonal.Twin hexagonal and two octagonal.

WELL COMPONENTS AND THEIR WELL COMPONENTS AND THEIR FUNCTIONS:FUNCTIONS:

Cutting Edge:Cutting Edge:

Provides a comparatively sharp edge to cut the soil below during sinking Provides a comparatively sharp edge to cut the soil below during sinking operation.operation.

Curb:Curb:

1.1. It has a two-fold purpose.It has a two-fold purpose.

2.2. During sinking it acts as an extension edge & also provides support to the During sinking it acts as an extension edge & also provides support to the well stein & bottom plug while after sinking it transfer the load to the soil well stein & bottom plug while after sinking it transfer the load to the soil now.now.

Steining:Steining:

1.1. It is the main body of the well. It is the main body of the well.

2.2. It also serves dual purpose. It also serves dual purpose.

3.3. It acts as a cofferdam during sinking & structural member to transfer theIt acts as a cofferdam during sinking & structural member to transfer the load to the soil below afterwards.load to the soil below afterwards.

Bottom Plug:Bottom Plug:

To transfer load from the steining to the soil below.To transfer load from the steining to the soil below.

Sand Filling:Sand Filling:

It is supposed to affored some relief to the steining by transferring It is supposed to affored some relief to the steining by transferring directly a portion of load from well cap to the bottom plug.directly a portion of load from well cap to the bottom plug.

Top Plug:Top Plug:

Serves as shuttering for laying the well cap.Serves as shuttering for laying the well cap.

Reinforcement:Reinforcement:

Provides requisite strength to the structure during sinking & service.Provides requisite strength to the structure during sinking & service.

Well Cap:Well Cap:

To transfer the loads & moments from the pier to the well or wellsTo transfer the loads & moments from the pier to the well or wells below.below.

PROBLEMS IN WELL PROBLEMS IN WELL SINKING:SINKING:

1.1. Sand Blowing: Sand Blowing:

The trouble of sand blowing takes place during the process of dewatering of The trouble of sand blowing takes place during the process of dewatering of the well passing through sandy strata.the well passing through sandy strata.

The fall of sand in the caisson is so sudden and huge that it amount to a depth The fall of sand in the caisson is so sudden and huge that it amount to a depth of about 3 to 15 m of sand.of about 3 to 15 m of sand.

2. 2. Tilting of well:Tilting of well:

When a well sinks more or one side than the other then it is known to have When a well sinks more or one side than the other then it is known to have tilted.tilted.

The tilting is mainly due to unequal dredging and non uniform bearing power The tilting is mainly due to unequal dredging and non uniform bearing power of soil.of soil.

Following method may be Following method may be employed to bring tilted well in employed to bring tilted well in

positionposition Control of dredgingControl of dredging

Eccentric LoadingEccentric Loading

Water JettingWater Jetting

Pulling the wellPulling the well

Pushing by JacksPushing by Jacks

Use of explosivesUse of explosives

Deposition of Earth on one side and excavation on otherDeposition of Earth on one side and excavation on other

Providing temporary obstacle below the cutting edgeProviding temporary obstacle below the cutting edge

Shifting of Wells:Shifting of Wells:

The shifts change span lengths and thereby induce eccentric loads on the The shifts change span lengths and thereby induce eccentric loads on the welll steining and the foundation.welll steining and the foundation.

The magnitude of the ill effects depends upon the size of the well and depth The magnitude of the ill effects depends upon the size of the well and depth to which it is sunk.to which it is sunk.

If a simple tilt occurs at a certain depth and the sinking continued till If a simple tilt occurs at a certain depth and the sinking continued till designed foundation depth is reached, the shift at the bottom could be greater designed foundation depth is reached, the shift at the bottom could be greater than at top.than at top.

The following precautions should The following precautions should be taken to avoid tilts and shifts be taken to avoid tilts and shifts

during sinking operations:during sinking operations:

The outer surface of the well curb and steining should be as regular and smooth The outer surface of the well curb and steining should be as regular and smooth as possible.as possible.

The radius of curb should be kept 2 to 4 cm larger than the outside radius of well The radius of curb should be kept 2 to 4 cm larger than the outside radius of well steining.steining.

The cutting edge of the curb should be uniform in thickness and sharpness.The cutting edge of the curb should be uniform in thickness and sharpness.

The dredging should be done uniformly.The dredging should be done uniformly.

BOX CAISSONS:BOX CAISSONS: A box caisson is open at top and closed at bottom.A box caisson is open at top and closed at bottom. It is merely a variation of the suspended type cofferdam.It is merely a variation of the suspended type cofferdam. The box caissons may be built of reinforced concrete, steel or timber.The box caissons may be built of reinforced concrete, steel or timber.

PNEUMATIC CAISSONS:PNEUMATIC CAISSONS: A pneumatic caisson is open at bottom and closed at the top.A pneumatic caisson is open at bottom and closed at the top. This is useful at location where it is not possible to adopt well.This is useful at location where it is not possible to adopt well.

They are suitable when depth of water is more than 12 m.They are suitable when depth of water is more than 12 m.

The maximum depth of water up to which pneumatic caisson can be used is The maximum depth of water up to which pneumatic caisson can be used is limited from the consideration of health of the workers.limited from the consideration of health of the workers.

In this method the compressed air is used to remove from the working chamber In this method the compressed air is used to remove from the working chamber and the foundation work is carried out in dry conditions.and the foundation work is carried out in dry conditions.

They can be made of timber, steel.They can be made of timber, steel.

COFFERDAMSCOFFERDAMS

““Cofferdams are temporary structures designed to exclude both surfaceCofferdams are temporary structures designed to exclude both surface water and ground water from the excavation area.”water and ground water from the excavation area.”

They provide an impermeable structure around the periphery of theThey provide an impermeable structure around the periphery of the

construction area resulting in relatively dry work space.construction area resulting in relatively dry work space.

Requirement of a cofferdam:Requirement of a cofferdam:

It should be reasonably water tight.It should be reasonably water tight.

The total cost of the construction, maintenance and pumping is the minimum.The total cost of the construction, maintenance and pumping is the minimum.

It should be generally constructed at site of work.It should be generally constructed at site of work.

It should be so planned as to facilitate any dismantling and reuse of materials.It should be so planned as to facilitate any dismantling and reuse of materials.

Types of cofferdam:Types of cofferdam:

Earth fill cofferdamEarth fill cofferdam

Rock fill cofferdamRock fill cofferdam

Rock fill crib cofferdamRock fill crib cofferdam

Single wall cofferdamSingle wall cofferdam

Double wall cofferdamDouble wall cofferdam

Cellular cofferdamCellular cofferdam

Selection of cofferdam:Selection of cofferdam:

Extent of area to be protected by a cofferdam.Extent of area to be protected by a cofferdam.

The depth of water to be dealt with.The depth of water to be dealt with.

Velocity of flowing water.Velocity of flowing water.

Nature of bed on which cofferdam is to rest.Nature of bed on which cofferdam is to rest.

Availability of construction materials in the vicinity of site of work.Availability of construction materials in the vicinity of site of work.

Transportation facilities available.Transportation facilities available.

CABLE ANCHORING

Anchors are constructed at locations around each caisson.

At anchor locations soil bearing was carried out by using rotary percussion type drilling equipment.

Construction:

The required depth of bearing near the caisson location was achieved by using a standard size of casing pipes of dia 135 mm, length 1500 mm & having thread at both ends and soil drilling was done by rotary percussion type drilling equipment.

GROUTINGGROUTING

““Grouting is a process of injecting the cement materials into the cracks Grouting is a process of injecting the cement materials into the cracks and seams of the rock or voids in the soil.”and seams of the rock or voids in the soil.”

It strengthens and makes the rock or soil water tight and monolithic.It strengthens and makes the rock or soil water tight and monolithic.

It has been successfully used in stopping the leakage from rocks.It has been successfully used in stopping the leakage from rocks.

Portland cement grout is useful for crack upto 1.6 mm width only.Portland cement grout is useful for crack upto 1.6 mm width only.

Methods:Methods:

Cement groutingCement grouting

Chemical process or chemical groutingChemical process or chemical grouting

Cement grouting:Cement grouting:

In this a mixture of cement, sand and water is used.In this a mixture of cement, sand and water is used.

Numbers of holes are drilled in the ground.Numbers of holes are drilled in the ground.

Then they are filled by the cement grout under pressure.Then they are filled by the cement grout under pressure.

The grouting is continued till no grout comes through the hole.The grouting is continued till no grout comes through the hole.

Chemical grouting:Chemical grouting:

In this a concentrated solution of sodium silicon and calcium In this a concentrated solution of sodium silicon and calcium chloride as electrolyte.chloride as electrolyte.

Types of chemical grouts:Types of chemical grouts:

Inorganic chemicalsInorganic chemicals

Organic chemicalsOrganic chemicals

SHEET PILESSHEET PILES

Steel Sheet piles walls are constructed by driving steel sheets into a slope or Steel Sheet piles walls are constructed by driving steel sheets into a slope or excavation.excavation.

They are considered to be most economical where retention of higher earth They are considered to be most economical where retention of higher earth pressures of soft soils is required.pressures of soft soils is required.

Their most common use is within temporary deep excavations.Their most common use is within temporary deep excavations. It consists of small sheet sections of steel that are 10 to 15 mm thick.It consists of small sheet sections of steel that are 10 to 15 mm thick.

They are driven into the soil to provide support during excavation.They are driven into the soil to provide support during excavation.

Each sheet is joined to the adjacent sheet by means of an interlocking joint.Each sheet is joined to the adjacent sheet by means of an interlocking joint.

Types of sheet pile walls:Types of sheet pile walls: CantileverCantilever AnchorAnchor ProppedPropped

DEEP EXCAVATIONDEEP EXCAVATION

“ “The excavation of trenches which required side support & dewatering is termed The excavation of trenches which required side support & dewatering is termed as deep excavation.”as deep excavation.”

In case of ordinary excavation In case of ordinary excavation

No support is required to support the sides of trenchesNo support is required to support the sides of trenches

No water is met with during the process of excavationNo water is met with during the process of excavation

The depth of excavation will entirely depend on the type of soil.The depth of excavation will entirely depend on the type of soil.

If the soil is firm and hard, the depth of excavation is less.If the soil is firm and hard, the depth of excavation is less.

If the soil is soft & loose, the depth of excavation is more.If the soil is soft & loose, the depth of excavation is more.

Excavation beyond a depth of 1.5 m is generally treated as deep excavation.Excavation beyond a depth of 1.5 m is generally treated as deep excavation.

Problems faced in deep excavations:Problems faced in deep excavations:

Prevention of the collapsing of sides of the trench. It is solved by adopting Prevention of the collapsing of sides of the trench. It is solved by adopting a suitable method of timbering.a suitable method of timbering.

Prevention of water oozing or coming out from the sides or bottom of the Prevention of water oozing or coming out from the sides or bottom of the trench. It is solved by applying a suitable method of dewatering the trench. It is solved by applying a suitable method of dewatering the trenches.trenches.

Timbering of trenches:Timbering of trenches:

1. Stay Bracing1. Stay Bracing

2. Box Sheeting2. Box Sheeting

3. Vertical Sheeting3. Vertical Sheeting

4. Runners4. Runners

5. Sheet Piling5. Sheet Piling

DEWATERING OF FOUNDATION EXCAVATIONSDEWATERING OF FOUNDATION EXCAVATIONS

““The process of removing the water from the trench is known as dewatering.”The process of removing the water from the trench is known as dewatering.”

Methods to dewater deep excavationsMethods to dewater deep excavations

Sumps & DitchesSumps & Ditches

Well Point SystemWell Point System

Deep well systemDeep well system

Vacuum MethodVacuum Method

Cement GroutingCement Grouting

Chemical ProcessChemical Process

Freezing ProcessFreezing Process

Electro-Osmosis processElectro-Osmosis process

IMPORTANT QUESTIONSIMPORTANT QUESTIONS1)1) what is meant by jacking (Box & Pipe)?what is meant by jacking (Box & Pipe)?

2)2) What is meant by trenchless technology?What is meant by trenchless technology?

3)3) At what conditions, we are going for under water construction?At what conditions, we are going for under water construction?

4)4) What is the purpose of diaphragm wall?What is the purpose of diaphragm wall?

5)5) What are the different types of tunneling techniques?What are the different types of tunneling techniques?

6)6) Define pile and list out its types.Define pile and list out its types.

7)7) What is the purpose of pile cap?What is the purpose of pile cap?

8)8) What are the equipments used during tunnel techniques?What are the equipments used during tunnel techniques?

9)9) Define caisson.Define caisson.

10)10) Define cofferdam.Define cofferdam.

11)11) What are the sequential activities that will be carried out during driving well and caisson What are the sequential activities that will be carried out during driving well and caisson at the construction pile?at the construction pile?

12)12) What is the function of sheet piles?What is the function of sheet piles?

13)13) Define shoring.Define shoring.

14)14) Why shoring is adopted for deep cutting?Why shoring is adopted for deep cutting?

15)15) What is the purpose of reservoir?What is the purpose of reservoir?

16)16) What are the different types of geomembrane?What are the different types of geomembrane?

17)17) Why membranes are required for large construction of reservoir construction?Why membranes are required for large construction of reservoir construction?

18)18) Give some examples of substructure construction.Give some examples of substructure construction.

19)19) What is the purpose of well points?What is the purpose of well points?

20)20) What is meant by dewatering?What is meant by dewatering?

21)21) Give an example for underground open excavation.Give an example for underground open excavation.

22)22) What is meant by stand by plant equipment?What is meant by stand by plant equipment?

23)23) List out the projects where you require dewatering.List out the projects where you require dewatering.

24)24) What are the equipments used during shoring?What are the equipments used during shoring?

25)25) What are the difference between driven piles and bored piles at the point of What are the difference between driven piles and bored piles at the point of construction view?construction view?

26)26) What are the difference between sheet piles and diaphragm walls?What are the difference between sheet piles and diaphragm walls?

27)27) What is grouting?What is grouting?

1)1) Explain box jacking and pipe jacking techniques in detail.Explain box jacking and pipe jacking techniques in detail.

2)2) Explain tunneling techniques in detail.Explain tunneling techniques in detail.

3)3) Bring out briefly the various piling techniques.Bring out briefly the various piling techniques.

4)4) Explain the construction with help of diaphragm walls, basements and sheet Explain the construction with help of diaphragm walls, basements and sheet piles and bring out difference between them.piles and bring out difference between them.

5)5) Explain in detail the under water construction sequences.Explain in detail the under water construction sequences.

6)6) Give a detailed description about various equipments used during driving well Give a detailed description about various equipments used during driving well and caissons, sinking cofferdam and shoring for deep cutting.and caissons, sinking cofferdam and shoring for deep cutting.

7)7) Explain about the dewatering techniques and the importance of well points in Explain about the dewatering techniques and the importance of well points in that in detail.that in detail.

8)8) Explain various grouting methods used in construction.Explain various grouting methods used in construction.

9)9) Explain deep excavation with its different methods of timbering in detail.Explain deep excavation with its different methods of timbering in detail.

10)10) Explain the problems in sinking of well.Explain the problems in sinking of well.

THANKING U