definition of tunnel boring

7/31/2019 Definition of Tunnel Boring

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D4 Teknik Perawatan dan Perbaikan Gedung

Teknik Sipil Politeknik Negeri Bandung

Chapter II

TUNNEL BORING MACHINE

Definition of Tunnel Boring MachineA tunnel boring machine (TBM) also known as a "mole", is a machine used to excavate

tunnels with a circular cross section through a variety of soil and rock strata. They can bore

through anything from hard rock to sand. Tunnel diameters can range from a metre (done

with micro-TBMs) to 19.25 m to date. Tunnels of less than a metre or so in diameter are

typically done using trenchless construction methods or horizontal directional drilling rather

than TBMs.

Tunnel boring machines are used as an alternative to drilling and blasting (D&B) methods in

rock and conventional "hand mining" in soil. TBMs have the advantages of limiting the

disturbance to the surrounding ground and producing a smooth tunnel wall. This significantly

reduces the cost of lining the tunnel, and makes them suitable to use in heavily urbanized

areas. The major disadvantage is the upfront cost. TBMs are expensive to construct, and can

be difficult to transport. However, as modern tunnels become longer, the cost of tunnel

boring machines versus drill and blast is actually lessthis is because tunneling with TBMs

is much more efficient and results in a shorter project.

The largest diameter TBM, at 19.25 m, built by Herrenknecht AG for a recent project in

Orlovski Tunnel, St.Petersburg. The machine was built to bore through soft ground including

sand and clay. The largest diameter hard rock TBM, at 14.4 m, was manufactured by The

Robbins Company for Canada's Niagara Tunnel Project. The machine was used to bore a

hydroelectric tunnel beneath Niagara Falls, the machine has been named "Big Becky" in

reference to the Sir Adam Beck hydroelectric dams to which it is tunnelling to provide an

additional hydroelectric tunnel.

Type of Tunnel Boring Machine

From the geological condition, tunnel boring machine divided into 4 class

1. Open Hard Rock TBMsOpen hard rock TBMs are designed for use in hard, stable rocks. These machines tunnel

through the rock and use a complex system of hydraulics to pull themselves along
http://en.wikipedia.org/wiki/Tunnelhttp://en.wikipedia.org/wiki/Stratumhttp://en.wikipedia.org/wiki/Boring_%28earth%29http://en.wikipedia.org/wiki/Sandhttp://en.wikipedia.org/wiki/Trenchless_technologyhttp://en.wikipedia.org/wiki/Directional_boringhttp://en.wikipedia.org/wiki/Drilling_and_blastinghttp://en.wikipedia.org/wiki/Herrenknechthttp://en.wikipedia.org/wiki/Niagara_Tunnel_Projecthttp://en.wikipedia.org/wiki/Niagara_Fallshttp://en.wikipedia.org/wiki/Adam_Beckhttp://en.wikipedia.org/wiki/Adam_Beckhttp://en.wikipedia.org/wiki/Niagara_Fallshttp://en.wikipedia.org/wiki/Niagara_Tunnel_Projecthttp://en.wikipedia.org/wiki/Herrenknechthttp://en.wikipedia.org/wiki/Drilling_and_blastinghttp://en.wikipedia.org/wiki/Directional_boringhttp://en.wikipedia.org/wiki/Trenchless_technologyhttp://en.wikipedia.org/wiki/Sandhttp://en.wikipedia.org/wiki/Boring_%28earth%29http://en.wikipedia.org/wiki/Stratumhttp://en.wikipedia.org/wiki/Tunnel


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through the tunnel as they dig. They do not have built-in systems for reinforcing the

tunnels they dig, relying on the structural integrity of the rock to support itself.

2. Shielded Hard Rock TBMsShielded TBMs are designed for operation in hard rocks that are not stable or have a highdegree of fracturing, making cave-ins likely. These single shield TBMs have a system of

automated machines which place concrete segments on the tunnel wall as a reinforcing

sheath as they dig. These machines cannot propel themselves like open TBMs; they can

only push off from the concrete segments they lay as they go along. A special type of

shielded TBM called a double shielded TBM is designed to work in either type of

condition. These machines are used where engineers expect to encounter both stable and

fractured rock during a tunnel project.

3. Soft Ground TBMsSoft ground TBMs are designed for tunneling through softer types of earth like clays,

soft rocks like sandstone, and loose or very wet ground. Earth pressure balance TBMs

use sophisticated controls to maintain a balance between forward motion and excavated

material to keep the tunnel stable. Soil stabilizers are often injected into the surrounding

soil or soft rock to help keep it stable. Slurry shield TBMs operate in soils or rocks that

are exceedingly wet, or even saturated. Some of these machines are completely airtight,

and use a slurry and pump system to remove excavated material. Both types of soft

ground TBMs are shielded; they lay a sheath of concrete segments as they go.

4. Raise and Shaft BoringRaise and shaft boring TBMs are used for tunneling vertically; these machines dig

ventilation shafts, access shafts, and maintenance shafts as well as traditional mine shafts

and drainage tunnels. These machines are designed in much the same way as other

TBMs, but are made to tunnel vertically instead of horizontally or nearly so.

And form Herrenknecht AG (the world market leader in mechanized tunneling), there are a

lot of type of tunnel boring machine, divided from their purpose

Soft Ground EPB TBM Soft Ground Mixshield TBM Hard Rock Gripper TBM


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Hard Rock Single Shield TBM Hard Rock Double Shield TBM Hybrid Convertible TBM

Pipe Jacking / Microtunnelling TBM Horizontal Directional Drilling (HDD) rigs Vertical Shaft Sinking Machines

The Component of Tunnel Boring Machine

Major Component of Tunnel Boring Machine


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The Main Sensors1. Face pressure

It is the most important sensor for EPB Shield machine excavation. The machine

applies suitable pressure to the excavation chamber in order to balance the shield

pressure against earth pressure, thus avoiding overexcavation.

2. Cutter motor sensorThere are various types of geological conditions such as weathered rock, sand, clay and

residual soils. The cutter-motor sensor determines proper operation in order to

excavate, as well as a guide whether cutter pressure or excavation speed should be

increased or reduced. It all depends on this cutter-motor sensor.

3. Screw conveyor sensorThe excavated soil is conveyed from the chamber to the screw conveyer. To maintain

the ideal face pressure the revolution speed of the screw-conveyor and hydraulic oil

pressure is adjusted during excavation. In addition, the screw-conveyor discharge gate

opening hydraulic pressure and ratio are also monitored.

4. Shield jack sensorThe TBM uses jacks to push against installed segments to move the TBM forward. The

condition of the earth being excavated can be judged from the total thrust of these

shield jacks. Also, it is the most important part in controlling the direction of the TBM

machine. Based on the alignment design, suitable jacks shall be used. The stroke of the


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jack influences the excavation length. Thus the excavation speed is controlled by the

speed of the jack stroke.

These sensors are very important to manage the TBM excavation, but all depends on various

ground conditions and water levels. Therefore information gathered from these sensors willbe studied and decided for the following excavation parameters.

Tunnel Guidance System

The TBM guidance system used is common in Japan for similar tunnels, due to working

space constraints. As such, a Gyro for horizontal control and water level system for vertical

control were adopted. These two sensors are used in the guidance control system of the TBM.

The two systems are described as follows.

Water level sensor.

The measurement unit is connected to the control unit with a hose. The control unit is

connected with hose drums and this hose drum and standard units are connected to

these drums. The hoses extend automatically as the excavation distance increases. The

measurement unit is set up inside the TBM, and the control unit and hose drums are set

up in the backup car. It is then fitted to a standard unit on the segment behind the

backup car. Water is filled in these hoses and the water level difference between the

measurement unit and a standard unit is measured and thus vertical control of TBM

machine is observed. This is done for every 1m excavation. Concurrently, 1m of the

hose will be extended. It is possible to excavate along an incline if the excavation

control is adjusted according to an increase in water level in the valve of 1mm, which

means that once excavation has been carried out over 1m the TBM will have traveled

up 0.1%. This information will be observed by the TBM operator and he will guide the

TBM to its correct position and alignment.


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1. Measurement unit2. Control unit3. Hose drum4. Standard unit

Tunnel Boring Machine Systems

Pre-construction Stage

Identified the geographical extent of the construction works involved and designed a scheme

of survey control network to cover the area .

(Step 2 of 4)

Carried out a reconnaissance survey on site to identify the known control stations nearby and

established the new survey stations


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(Step 3 of 4)

Set up a survey control network, the new stations were rigidly tied to the known stations. All

field measurements were to meet the following acceptance criterias before computation was

performed.

(Step 4 of 4)

Carried out field measurements of angle and distance among the stations followed by

computation of global coordinates of control stations. All field measurements were to meet

the following acceptance criterias before computation was performed.


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Construction Stage

(Step 1 of 5)

Prior to the initial drive of TBM, secondary control station was established at the TBM

Launching Shaft at surface by transferring co-ordinates from the primary control stations.

(Step 2 of 5)

Transferred the secondary control station from surface at the TBM Launching Shaft to the

tunnel control station at underground level


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(Step 3 of 5)

Moved up the tunnel control station by Double Zigzag Traverse behind the TBM as the

machine travelled ahead, and transferred a temporary station to the shoulder position of the

erected ring at the back-up gantry of the TBM

(Step 4 of 5)

Traversed the temporary control stations at the erected rings above the TBM back up gantry

to reach the Laser Station located about 30m behind the TBM.


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(Step 5 of 5)

The Laser Station carried the coordinates from the control station shot the prism target

affixed to the bulkhead of TBM to determine the absolute spatial coordinates (x,y,z) of the

TBM at that point. The tunnel guidance system and the dual axial inclinometerssimultaneousely measured the amount of rotation along the three perpendicular axis of the

TBM to determine the orientation of the heading of the machine.

The Effects Of Tunnelling

The rate of progress of the TBM depended on the working hours of the TBM. This also

dictated the duration that residents would hear and feel the TBM working under their

properties. As an approximate guide to the duration of noise, based on the TBM working twoshifts or 16 hours, and the machine progressing at a rate of 10m per working day, residents

typically heard the TBM over a period of approx three working weeks. For Example if the

TBM was to work one shift or 8 hours per day it would only progress at an average of 5

metres per day and residents will experience the machine over a period of 6 weeks and

similarly, if they worked 24hrs, the time would be reduced to 10 days.


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Other Construction Noises

Other work activities may from time to time caused noise, which was audible tohouseholds above the tunnel works; these work items include.

Rock condition probing, this is where the tunnellers drill a narrow (50mm diameter)hole 30m in advance of the TBM to confirm the condition of the rock ahead, this

occured approx every 3rd working day.

Excavating tunnel cross passages. Every 250m a cross passage is constructed betweenthe tunnel tubes using traditional tunnelling methods. Every kilometre a vehicle cross

passage is also formed. This work would normally be carried out approx 750m behind

the cutter head.

Other minor excavations to the side of tunnel tubes, such as forming the fire hose reeland emergency telephone niches.

Maintenance of the rock cutting head


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Vibrating rollers, used to compact the road fill, approx 15% of the tunnel is backfilledto give a flat road surface, the roller works approx 200m behind the TBM cutter head.


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Comments from Independent Geologist

From time to time Dublin City Council has availed of the services of an Independent

consultant to help allay resident concerns. Pre-tender, he met with resident leaders in Marino

and assure them that site investigation works would not damage their properties.

Dublin City Council availed of his services again in relation to concerns about the TBM. His

report mentioned that while the noise heard in houses above the TBM (when it is in the 45

minute rock cutting cycle) is clearly discernible, the noise/vibration levels were not in

themselves damaging to properties. He explained that they were similar to and in some cases

less, than those he experiences in his own property, which is situated under the flight path at

Heathrow.

What to expect when TBM is operating under a residential area The cutting head of the11.8m diameter-boring machine rotates approx three and half times a minute, the cutting head

has a series of disc shaped teeth which scores and grind the rock face. The rock debris is

collected onto a conveyor, which then transports the broken stone back to storage sheds on

the surface; trucks then transport the rock to quarries to reuse.

The noise energy caused by the TBM excavation process is transmitted through overlying

rock and boulder clay and is picked up by houses above. This ground borne energy manifests

itself in houses as both medium levels of noise and low levels of vibration.

During the day residents typically hear the TBM in approx 45-minute cycles, first it cuts

through the rock, then the noise stops for about 45 minutes while the machine installs the pre-

cast structural concrete lining. As the graphics try to show the noise levels gradually build up

over a period of time and when the machine is directly under residents houses, levels of up

to 55dB may be heard. Residents above the TBM also experience low levels of vibration

averaging at about 1.00 mm/sec (PPV) and peaking up to 1.5 mm/sec. Depending on the

working hours of the machine, and the size of peoples gardens it typically takes between one

and three days for the machine to move from property to property.

The vibration effect of the structural borne noise/vibration can be felt by placing your hand

on the concrete walls of the properties or it may be picked up in radiators and such like,

particularly when the TBM is coring under or very near a property

definition of tunnel boring

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