Important Question And Answer: Civil - Sub Structure Construction

SUB STRUCTURE CONSTRUCTION

1. What are the techniques used in Box/Pipe Jacking?

Techniques used in Box/Pipe jacking requires the construction of just two pits: The Trust

Reception pits

Dimensions of the pits vary according to site conditions.Excavation of soil can be by manual or mechanical means depending on the type of machines used.

2. Give the applications of Box Jacking?

The applications of Box Jacking are: Underground Pipes

Ducks and culverts

3. Give the advantages of Box/Pipe Jacking?

The advantages of Box/Pipe Jacking are:

Environmentally friendly with minimal damage to the surface. Highly accurate and cost effective.

Suitable for all kinds of profiles for a wide variety of soil conditions. Traffic congestion and additional pollution will not cause. Extremely suitable for all kinds of underground utility infrastructure.

4. List the disadvantages of Box/Pipe Jacking?

The disadvantages of Box/Pipe Jacking are:

Limited tunnel run resulting in more required shafts (approximately every 1000 ft). Relatively straight alignment required (minimum radius of curvature approximately 400ft).

Difficulty in replacing damaged pipe.

5. When is Diaphragm walls used?

A diaphragm wall is basically a deep trench excavated in soil in to which reinforced concrete is placed.Diaphragm walls are used in permanent and temporary foundation walls for deep basements in earth retention schemes for highway and tunnel projects,as permanent walls for deep shafts for tunnel access,and as permanent cut-off walls through the care of earth dams.

6. Give the uses of diaphragm walls?

To provide structural support for the construction of building basements with underground parking.

To provide stability to landslide ,highway cuts,and deep building excavations including shafts.

To provide retaining walls in areas where severe limitations may be posed by noise,vibration,geology,water table and schedule.

7. What is a tunnel?Give the advantages?

A tunnel is defined as an underground passage for transport of passengers,water,sewage,minerals,gas,etc.

Advantages:-

The society of tunnel construction is increased by the improved modern methods of construction.

It is more economical than open cuts beyond certain depths.

8. What are the factors you will consider while selection of route in tunneling?

a)     Geological conditions

b)     Right of way

9. Give the various methods of tunneling through rock .

The various method of tunneling through the rocks are:

Full face method

Heading and bench method

Cantilever car pump method

Drift system

Pilot tunnel method

10.Give the various methods of tunneling through soft ground.

The various methods of tunneling through the soft ground are:

a)     Fore paling method

b)     Needle beam method

c)      Five piece set method

d)     Linear plates method

e)      Other methods

•        Casting methods

•        Square sets and logging method

•        Horse cups method

11.What is cofferdam?

A cofferdam is defined as a temporary structure which is constructed.So,as to remove water/soil from an area and make it possible to carry on the construction work under reasonably dry conditions.

12.What are the uses of cofferdams?

To facilitate pile driving operations.

To place grillage and raft foundations.

To construct foundations for piers and abutments of bridges,dams,locks,etc,

13.What are the factors you will consider while selecting cofferdams?

The factors considered while selecting cofferdams are: The area to be protected by a cofferdam.

The depth of coater to be dealt with i.e, shallow depth of deep depth. The possibility of overtopping by floods,tides,etc.

The nature of bed on which the cofferdam is to test,(i.e;) previous layer or an impervious layer.

14.What are the types of cofferdams?

The types of cofferdams are: Dikes

Single wall construction Double wall construction Cellular cofferdam Rock-filled Concrete cofferdam Suspended cofferdam

15.Give the different types of piling?

Rotary board technique

Continuous flight Augur piling

Low head room continuous Augur pile

16.What is grouting?

Grouting is an engineering and art combined to fill up the voids or cavities in rock or soil masses with fluid that will increase the overall strength and impermeability of the mass.

17.Give the types of grouting.

Chemical

Cement

Jet grouting

18.Give the characteristics of grouting materials.

The characteristics of grouting materials are:

The grouting material has high permeability. No vibrations are used.

Application requires no additional structure used.

The properties are measurable.

It has high strength and low deformability.

19.            What is caisson ?

The word caisson is derived from the French word 'caisse' meaning a box. In civil Engineering, a caisson is defined as a structure which is sunk through ground or water. They exclude water and semi fluid material during the process of excavations of foundations and which subsequently becomes an integral part of the substructure.

20.Give the uses of caissons.

The uses of caissons are:

To reach the hard bearing structure for transferring the load coming on support for bridge piers and building columns.

To serve as an impervious core wall of earth dams.When placed adjacent to each other. To provide an access to a deep shaft or a tunnel.

21.What is the difference between cofferdams and caissons?

The difference between cofferdams and caissons are:

The main difference between a cofferdam and a caisson is that the former is a temporary structure while the latter forms the part of the permanent work.

A cofferdam becomes uneconomical in cases where the place of the foundation work and small as compared to the depth of water under such circumstances ,caissons are most suitable.

The places at which cofferdam cannot be dewatered successfully,caissons are used.

22.What are the materials used for the construction of caissons?

Cast iron

Reinforced Cement concrete

Steel

Timber

24.What are the uses of sheet pile?

The uses of sheet pile are:

To protect river banks.

To retain the sides of foundation trenches.

To resist flow of underground or loose soil or of both.

To resist bending abrasion or other stresses which may arise in use.

25.Give the different types of sheet piles?

The types of sheet piles are: Concrete sheet pile Steel sheet pile Timber sheet pile

26.What is shoring?Why is it provided?

Shoring is the construction of a temporary structure to support temporarily an unsafe structure.

27.Why is shoring provided in foundation?

When a wall cracks due to unequal settlement of foundation and the cracked wall needs repair.So,shoring is provided in foundation.

28.Give the types of shoring in foundation.

Types of shoring foundation are: Sheet piling

Stay Bracings Box sheeting Vertical sheeting

29.What is dewatering?

The process of removal of water from an area where the ground water table is high .

30.            Give the methods of dewatering.

Ditches

Well point system

Shallow well system

Deep wall system

Vacuum method (forced flow method)

Electro osmosis method