Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
TBM CROSSING OF STATIONS
Eng. Marco Barbanti – Astaldi S.p.A.
Eng. Tommaso Grosso – Astaldi S.p.A.
18-11-2011
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
In the presence of groundwater the permeability of the ground is of great
interest. It is important to know if:
• the permeability of the ground is low or high
• there is any relevant heterogeneity , and which is the distribution of
individual formations with various permeability individual formations with various permeability
There are two main problems when the TBM is passing empty through the
waterbed layer of an already excavated station
•Opening the barrier at the entrance to each station for the TBM
•Preventing any water from flowing through the station
•The pre-existing buildings
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
A station or a shaft can be the starting point or the finishing end of a
TBM and it is important all the problems concerning logistics sites for
TBMs
TBM CROSSING OF STATIONS
The intermediate stations are subjected to the passage of the TBM.
It is important to pay attention to the aspects connected to the two
different ways of passing the stations by TBM:
•“void crossing” , where the station has already been built, at least as
far as the excavation and the main structures are concerned;
•“full crossing”, where the station volume has yet to excavated;
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
SOFT EYE WALLThe concept of soft eye wall is to install fiber glass cage in the
diaphpragm wall where the TBM will break in or break out .
In this way:
• TBM avoid to stop the excavation
•The TBM can easily penetrate the wall
•Cutting tools can cut the soft eye bars without problems
•No problem of destroying and wearing of cutting tools•No problem of destroying and wearing of cutting tools
•The TBM anyway during this penetration has to proceed slowly
and with care.
•The installation of soft eye bars is nowdays compulsory
•If you don’t install soft eye bars???
•
•
•
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
TBM CROSSING FULL STATION
If in the design has been expected to excavate the station not yet built, it means that the
TBM will excavated inside the future station a tunnel, that it will be demolished in future
when the excavation of the station will arrive to the depth of the tunnel.when the excavation of the station will arrive to the depth of the tunnel.
The excavation procedure has to consider the crossing of the perimetral walls entering in
the station end going out from the station.
The crossing of the station in this case is more safe because it is a functioning and
operative TBM and faster than crossing the station empty.
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
TBM CROSSING OF EMPTY STATION
Generally the most common method for TBM crossing of the stations is that of void
crossing and it can usually be foreseen in the design stage of the underground line.
In some instance, the construction of the stations can become more critical than the
excavation of the tunnel, in fact it can happen that the tunnel construction is ahead of
construction of the next station.
In this case:In this case:
• if the design has foreseen void crossing of the station, slowing down is necessary;
•In the worst case the TBM advance has to be stopped in front of the station because it is
not completely equipped for the TBM to pass through; this is an event that should be
avoided , not only because the risk connected to consequent delays in schedule but
moreover because of more general problems of making the tunnel safe ( a stopped TBM
under buildings or under road is more dangerous than a functioning and operative TBM)
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
VOID CROSSING vs FULL CROSSING
•station already built•delay in launch of TBM (waiting station building)•no possibilities to finish the station before to finish the tunnel• >entries• >communication
•launching TBM in advance •complete excavation and building of tunnel•>risk•> segments (rings) to demolish• delay in finish station building
VOID FULL
• >communication• > easy maintenance of TBM• >safety• < risk• > ventilation• passing by void station is slower –brak in / out and launching procedure (pushing frame..)• < segments to demolish
• delay in finish station building because before it is necessary to finish the tunnel•It is faster to cross the station –the only slow activity is break in/out the walls
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
BREAK IN AND BREAK OUT SYSTEMS
Soil improvement
� Break in and break out
False tunnel
�Break out break out
Lean concrete
�Break in and break out
Sealing system
�Break in and break out
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
TBM CROSSING OF EMPTY STATIONS
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
SOIL IMPROVEMENT – GROUTED BODY
Behind the walls which we install the sealing system, it will be also
executed a grout body of jet grouting piles or plastic piles, in order to make
safer, avoiding seepage water inside the station, the phase of break out of
the TBM from the station.
These concrete blocks are jet-grouted behind the shaft/station wall eye for
a length exceeding the shield length so that, when the last wall is crossed a length exceeding the shield length so that, when the last wall is crossed
through, the TBM shield has already bored and one or two rings have
already been erected within the block itself, thus ensuring water seal.
The objectives of soil improvement are:
•to obtain a reduction of soil permeability through voids permeation and soil
structure compaction;
•to increase soil strength, consolidating loose materials to avoids
overbreaks when tunnelling with no face pressure applied.
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
Jet Grouting is a ground modification technique used to create in situ
cemented soil, inserting an injecting tube into the ground which has
a nozzle disposed for directing a jet of fluids or binders at an angle
inclined to the axial direction of the injecting tube. The jet of the fluids
or binders is discharged through the nozzle generally at a velocity of
100-450 m/sec and at a pressure of 50-1000 kg/cm2.
JET GROUTING
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
LEAN CONCRETE FOR BREAK IN
This system is a concrete blocks poured inside the station, attached to wall eye
for a length exceeding the shield length so that, when the last wall is crossed
through, the TBM shield is coming inside the body of the station avoiding
possible water seepage from groundwater behind the walls.
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
FALSE TUNNEL FOR BREAK OUT
The utility of the false tunnel is to have the TBM already inside a concrete
structure, inside a station, before to start the excavation. In this way the TBM
“has already bored” and one or two rings have already been erected within the
block itself, thus ensuring water seal, entering in the natural soil.
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
SEALING SYSTEM
A metal ring system provided with hydraulic seal, allowing to bore the shaft
wall with groundwater behind it.
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
This is an alternative to tunnel-end grouting consolidation, and allows to carry out
launch phase (as in this case) and the run-out phase from a Shaft or Station,
through a system of seals waterproofing the area around the TBM's shield thus
preventing possible water seepage from groundwater behind the walls.
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
The reception (or run-out) phase is much more complex than the start
phase, mainly due to the following reasons:
•High-precision in TBM topographical guidance is required: it must be
ensured that, when going through the metal ring, the shield's position
has the lowest possible plano-altimetric deviation with respect tohas the lowest possible plano-altimetric deviation with respect to
design. In fact, seal centering may be adjusted by means of hydraulic
jacks the maximum extension of which does not exceed 10 cm along its
radius.
•Pressure balance: after breaking through the wall, and up to going
through the seal, the pressure of possible water flows which may occur
around the shield because of the void between soil and the shaft
chamber, must be counter-balanced.
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
•Assembly of the equipment elements into the run-out shaft.
•Progress of TBM excavation under earth-pressure balance mode until the shield
runs into the grouted zone.
•Progressive reduction in pressure supporting the excavation face during the last
meters of excavation and until breaking through the last diaphragm
•Breakthrough and void crossing toward seals, while still keeping the cover
closed. During this phase, the following supplementary activities have to be
carried out:carried out:
�disassembly of peripheral tools, which might damage the seal;
�removal of muck accumulated in front of cutting head consequently to the
breakthrough,
�removal of provisional protections from the seal, in the invert area,
�topographic verification of the actual position of the cutting head with
respect to the metal ring.
•Cutting head goes through the seal and places pressure on it.
•Removal of the closing cover and subsequent translation of TBM shield up to
reaching disassembly position.
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
The use of the equipment offers the following advantages.
•Control of water inrushes: there is an intermediate phase, between the
breakthrough and pressurization of seal, during which it is necessary to balance
possible water inrushes from the hollow space between the shield and the soil.
•Reduction in soil consolidation from surface: in the case of shafts or stations, to•Reduction in soil consolidation from surface: in the case of shafts or stations, to
be crossed through as void volumes, in urban environments where the areas
required for grouted zone consolidation may be considerably limited, the
exploitation of such technology contributes to significantly reduce the dimensions
of grouted zone.
•Reclaimable equipment: the equipment installed as above is entirely reusable in
subsequent projects (obviously, apart from the shuttering pipe buried into the
concrete template), which makes it possible to compare this solution with
grouted body also from the economic point of view.
Course in Tunnelling and Tunnel Boring Machine
Kurs w zakresie drążenia tuneli oraz maszyny drążącej
THANK YOU FOR YOUR ATTENTION!!