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INTRODUCTION
Tunnel Boring Machine (TBM) also known as ‘MOLE’.
It is used to excavate tunnels with a circular cross section.
It can bore through anything from hard rock to sand.
Different types of TBMs are used for different geotechnology.
Used as an alternative to drilling and blasting (D&B) methods and conventional 'hand mining' in soil
Limits the disturbance to the surrounding ground and produces a smooth tunnel wall.
Suitable to use in heavily urbanized areas.
TBMs is also a complete single unit moving factory
Only little finishing work has to be done after using TBMs as this single unit can do
DRILLING SYSTEMS
CONCREATE SPRAYING
SEGMENTAL LINING
ROCK SUPPORTING
PIPE JACKING
CONVEYANCE OF EXCAVATED MATERIAL
GEOTECHNOLOGY
The geological and hydraulic information about the soil forms the basis for planning and executing tunnelling and pipe jacking projects.
Provide the basic data for selecting tunnelling methods and cutting wheel tools that will cut through the native ground efficiently and economically.
The most important ground or rock-mechanical parameters for designing a tunnel boring machine are:
-grading curve -rock/clay mineralogy
-ground water penetration -quality of the rock
-consistency limits -hardness of the rock
CUTTING ROLLS
Cutting rolls are used to tear of the soil and rock from tunnel face.
They are mounted on the cutting heads.
Different types of materials are used for different ground condition.
They are placed radially, so as to have maximum efficiency.
They can revolve themselves in full 360 degree.
They can be replaced periodically.
They presses the tunnel face with a force of 26 tons
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TUNNEL BORING MACHINE
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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.
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.
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.
Types of tunnels
Public works tunnels:
Public works tunnel carry water, sewage or gas lines across great distances.
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.