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7/31/2019 Definition of Tunnel Boring
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Siti H. Fauziah
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/Tunnel7/31/2019 Definition of Tunnel Boring
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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