1. TUNNEL BORING MACHINE GUIDED BY: Vineeth SUBMITTED BY: Aswin Gopal.V.T
Lucturer
Mechanical department
SUBMITTED BY:
Aswin Gopal.V.T
Roll No:12
MES5
KMCT Polytechnic College

2. Introduction
A tunnel is a horizontal passageway located underground. Tunnels are created by the process called excavation. There are many different ways to excavate a tunnel, including manual labor, explosives, rapid heating and cooling or a combination of these methods. But all the above described methods can be hazardous in some way and hence are not risk-free. ‘Tunnel Boring Machine(TBM)’ is the best solution found by human to get rid of problems which can occur while excavation.

3. Introduction
Tunnel boring machines are used to excavate tunnels with a circular cross-section.
They can be used on any geologies.
They can bore tunnels of diameter 1-15 metre.
It made tunnel boring process risk free.

4. Introduction
A tunnel boring machine (TBM) consist of 1 or 2 shields (Large metal cylinders).
At the end of dhe shield, a cutting wheel is attached.
Behind the cutting wheel, there is a chamber and inside it there is a set of hydraulic jacks which push the TBM forward.
Behind the shield, ie at the finished part of the tunnel several support mechanisms such as control rooms, rails for dirt pemoval, slurry pipelines etc., can be set up.

5. Introduction
The cutting wheel usually rotate at a speed between 1rpm and 10rpm. The rotation speed is determined by engineers depending upon the geology and diameter of the tunnel.
The mud formed while drilling is removed either by making it a slurry and then through pipelines or by using a conveyer belt or rail system.
Many disadvantages of D&B system of tunnel boring(Drill & Blast) can be avoided by using a TBM.

6. Hard Rock TBM

7. Hard Rock TBM
In hard rocks either shielded type or open type TBM can be used. For an open type TBM, no shield will be there.
The TBM’s disc cutters create compressive stress fractures and causes the rock to chip away. The chipped rock particles are called muck. Muck is removed through openings in cutter disc to conveyer belt system, which removes it from the tunnel.
Facility to lay supports such as ring beams, steel strips, wire mesh etc., are provided in Hard Rock TBM.

8. Soft Ground TBM They are of 2 types:
1) Earth Pressure Balance Machines(EPB)
2) Slurry Shield(SS)

9. Soft Ground TBM
EPB is used in ground with less than 7bar pressure. It use a combination of a disc cutter and cutting bits, Both made of Tungsten Carbide. EPB is capable to hold on soft ground by maintaining a balance between earth and pressure, and it has arrangements to supply additives such as Bentonite, Polymers, foam, etc.,
SS is used in places where there is high water pressure and large amount of ground water. It is of a fully enclosed type. It mixes the mud with the Bentonate slurry supplied and expells it through slurry pipelines. Large ‘Slurry separation plants’ are provided on ground surface to separate slurry and mud, and slurry is recycled back to tunnel.

10. Tunnel Boring Machine Facts
Weight: 800 tons
Length: 430 ft
Motors: 350 hp electric motor X 8 nos.
Energy required: 50,00,000 max output)
Cutter edge: 22ft dia, 60,000 pounds max thrust.

11. Tunnel Boring Machine Facts
Propel & Grip system:
This section performs 2 critical functions. It prevent the machine from sliding backward and also helps its forward movement.
Conveyor System: It transports rock fragments to the tail end of the tunnel boring machine, and From there these excavated material are transferred to rail cars which take them outside the tunnel.

12. Types of tunnels Mine Tunnels:
Mine tunnels are used to transport metal or mineral deporits extracted by mining activity. These tunnels may be roughly build and are made with low cost. They are for temperary use and is unsafe when compared to other types of mines.

13. Types of tunnels Public works tunnels:
Public works tunnel carry water, sewage or gas lines across great distances.

14. Types of tunnels
Transportation tunnels:
Rail and road transportation through tunnels are common nowadays. They may be through hills or even under oceans. TBMs were used to dig deep canals in olden times.

15. Tunnel construction
Workers use two methords in tunnel construction. Fullface mode and top-heading and bench mode.
In top-heading and bench mode they first bore a small tunnel , and then we bore underneath it. By this we can understand the stadility of rock before moving far forward.

16. Tunnel construction Hard rock:
While boring hard rocks, first workers dig a small hole on rock and place explosives in it. After detenerating it, the remove the muck, and repeat the same till it advance a little bit,and It’s only thenthe start the operation using a TBM.

17. Tunnel construction Sand ground (Earth)
In this type of excavation people have to dig soft
grounds of clay, silt, sand, gravel or mud. Here
‘stand-up-time’ (how long ground will stand safely
by itself) is of extream importance. Generally for soft grounds, stand-up tine is low and there is a risk of cave formation. To avoid this shields are used. They are cylindical srtuctures in which TBMs are placed. It give the tunnel a perfect round shape and help workers to install the permanent cast iron linings.

18. Tunnel construction
Tunnel engineers, must be familiar with on a tunnel.
Tension, which expands, or pulls on material.
Compression, which shortens or squeezes materials.
Shearing, which cause parts of materials to slide past one another in opposite directions.
Torsion, which twists a material.

19. Tunnel construction ‘Dead load’ and ‘Live load’
In order to remain static, tunnels must be able to withstand the loads placed on them. The load acting on a tunnel are of two types, namely ‘dead load’ and ‘live load’ The term dead load refers to the weight of the structure itself, while live load refers to the weight of the vehicles and people that move through the tunnel.
The tunnel must oppose these forces with strong materials, such as masonry, steel, iron and concrete.

20. Advantages of a TBM
Structural stability and safety at the face and work area.
Continous(non-cyclic) and fast operation.
Consistent, less skilled and easly trained operation.
Safer and pleasant working environment than D& B.
Less labours needed.

21. Disadvantages of TBM
High cost due to the need of supporting things such as conveyer belt, rails, slurry separating plant, slurry pipelines….. Etc,.
High cost of associated supplies.(Drill bits, TBM cutters, Blasting agents, …… etc,.)
TBM excavation rates are 4 to 6 times higher than D&B excavation.

22. THANK YOU