Downhole Drilling with Compressed Air - Kaeser Compressors

NEAT construction with Kaeser compressors
Downhole Drilling with Compressed Air
The Swiss, who are no strangers to bold engineering schemes, are currently building the ‘Gotthard Base
Tunnel’ after 50 years of planning. Forming the main section of the ‘Neue Eisenbahn-Alpen-Transversale’
(NEAT) new trans-alpine rail link, the tunnel has become Switzerland’s most ambitious construction project
yet: Miners carry out their work hundreds of metres below towering Alpine peaks and ridges to integrate the
Swiss railway system into the European high-speed rail network. Kaeser compressors are also on site to
assist with the tunnelling work at one of the most geologically challenging locations.
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At the Sedrun sub-section, two 6.5
km long tunnels run through the
project’s most complicated and difficult
geological zones. Also in this
section is one of the Gotthard Base
Tunnel’s two multifunction stations
that house crossovers, emergency
stop stations, and technical installations
for railway operations and
ventilation.
With more than 2000 metres of
overlying mountain, tunnelling
through the unstable rock of the
Tavetsch intermediate massif is particularly
demanding work. The
Sedrun section is reached from the
surface via a 1-km-long access tunnel
and two independent 800 metre
deep parallel vertical shafts. Heavy
duty conveying systems supply the
tunnelling site with machinery and
construction materials via shaft II,
whilst shaft I is used to bring the
excavated material to the surface.
At the foot of these shafts conventional
blasting and drilling techniques
are used, rock mass permit-
Special machinery:
the ‘Tamrock Axera T12 Sedrun’
ting, to advance tunnelling work
both north and south.
Specialised tunnelling in the
Tavetsch intermediate massif
Specialised blasting, drilling and
support procedures are used in the
Sedrun section to enable tunnelling
to progress through heavily loaded
zones in the Tavetsch intermediate
massif. Examples include:
� Round-blasting
� Tunnelling with full-faceheading
� Additional blasting (to create up
to 70 cm additional space) allows
for controlled deformation. This
requires heading diameters of up to
135 m² (normally: 68 m²)
� Systematic tunnelling face reinforcement
with long horizontal
anchors
� Initial reinforcement exclusively
with high-deformation capability
support materials (Design: steel
mountings with two interlocking
rings featuring slide joints, anchors)
� Application of rigid support material
(e.g. shotcrete) after deformation
has taken place
� Systematic use of additional support
material (additional anchors,
steel arches etc.) backwards from
the tunnelling face
� Implementation of further measures
such as grouting and advance
drainage
As deformable steel mountings had
never been used on this scale
before, extensive large-scale tests
at the construction site itself con-
ARGE Transco’s
“base camp” at
Sedrun
The Gotthard
railway line
today
Photos: SBB (3)
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A complete
tunnel system
takes shape
deep within the
mountain
Excavated
material is
carried to the
shaft via rail
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firmed that the theory worked in
practice.
To maximise the narrow workspace,
ARGE TRANSCO-Sedrun installed a
multi-functional heading installation
that is suspended from the tunnel
roof on a monorail system. In
use for the first time in tunnel construction
and more usually associated
with mining, the four multifunctional
machines create a second
work level for the placing of
steel arches, cutting of anchors at
the tunnelling face and also for
application of shotcrete at the tunnelling
face.
Special machines,
special service
Construction machinery supplier
Avesco AG, the representative for
Caterpillar and Sandvik-Tamrock in
Langenthal, was awarded the contract
to supply ten ‘Tamrock-Axera’
drilling jumbos, seven ‘Tamrock-
Toro’ front-loaders, four ‘Caterpillar’
special excavators, twelve ‘Rammer’
hydraulic hammers, as well as
‘Sandvik’ drilling steels. Avesco is
also responsible for supervision of
tunnelling equipment at the con-
struction site. Avesco Service Technicians
are permanently on-site and
work in three shifts, seven days a
week to provide round-the-clock
support for the machinery. Furthermore,
a spare parts and a drillingsteel
store are located underground,
as is an office container equipped
with its own IT infrastructure.
Drilling with air-power
A working group of representatives
from Arge Transco Sedrun, Avesco
Langenthal and Tamrock (Finland)
developed a special drilling installation
that would be able to tunnel
through the pressure zones of the
Tavetsch intermediate massif.
Weighing in at over 60 tonnes, the
giant ‘Tamrock Axera T12 Sedrun’
can sweep across the entire 13metre
tunnel diameter with its
drilling arms to set blast holes, selfdrilling
anchors, as well as cased
anchors, up to a drill diameter of
140 mm. For cased anchors, the
machines use the downhole drilling
method: Hydraulically driven via
push rods, the rotating drill-bit is
equipped with a pneumatically
powered hammer drill, which within
this diameter range, significantly
increases overall system efficiency.
Furthermore, it eases the burden on
the hydraulic drive system & bore
rods, enables precision drilling at
The compressed air for the ‘downhole
drilling’ process is produced here
low push rod speeds (10 to 60 rpm)
and simplifies setting of linear boreholes.
At the same time, the compressed
air used to power the downhole
drill-hammer also removes the drill
dust from the borehole and adding
dust-binding foam to the compressed
air prevents dust build-up.
Downhole drilling is a relatively new
process suited to large drilling
diameters and has proven particularly
effective both in extremely
hard and in soft rock masses.
Compressed air for the drill-bit
Kaeser rotary screw compressors
mounted on tunnel railcars provide
the compressed air that powers the
downhole drilling equipment at the
Sedrun construction site. This system
enables efficient compressed
air delivery exactly where it is needed,
as the air does not have to pass
through long sections of piping.
Each compressed air car is
equipped with two Kaeser CSDX
162 rotary screw compressors and
a 3000-litre air receiver per compressor.
Most of the condensate
that occurs during the compression
process is removed via centrifugal
Photo: SBB/AlpTransit Gotthard AG
Sedrun Section – Facts and Figures
· Two tunnels approx. 6.5 km long with 50 m
separation
· Connecting galleries every 320 m
· Multifunction station with two emergency stops
· Total length of tunnelling approx. 20 km
· Cost: 1.25 billion CHF
· Workforce: up to 450 employees
· Installation work: May 2002 to October 2003
· Shaft II construction: May 2003 to February
2004
· Tunnel blasting begins: July 2003 (North side),
August 2004 (South side)
· Estimated breakthrough: Summer 2008 (North
side), Autumn 2008 (South side)
· Completion of blasting: End 2008
· Concreting and finishing: 2006 to 2009
· Handover to owners: Summer 2011
separator, whilst ‘Eco Drain’ condensate
drains ensure ecologically
sound disposal. For equipment to
operate reliably and efficiently in
such a hostile working environment,
meticulous design and construction
are essential. Kaeser compressors,
for example, feature large
low-speed airends filled with generous
volumes of cooling / lubricating
fluid to ensure effective removal of
particles from the intake air.
As a result, Kaeser compressors
provide far superior performance
and reliability compared with units
equipped with smaller high-speed
airends. This advantage is further
enhanced by Kaeser’s use of a
maintenance-free 1:1 direct drive
coupling to turn the airend, as this
eliminates the power losses associated
with gear driven systems.
With unrivalled quality and dependability,
Kaeser compressors are in
their element performing such a
demanding role at what is one of
the world’s most challenging construction
sites.
Author: Klaus Dieter Bätz
Contact: klaus-dieter.baetz@kaeser.com
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