Risk Management in Action Controlling Difficult Ground by Innovation
A. Moergeli moergeli + moergeli consulting engineering, CH-8716 Schmerikon/Switzerland mailto:firstname.lastname@example.org, http://www.moergeli.com
ABSTRACT: The Swiss are currently building the worlds longest tunnel, the 35-mile long Gotthard Base
Tunnel. At Sedrun, for the first time in tunneling, four Roadway Support Machines will drive through
most difficult ground, supporting variable diameters of up to 13 m. The machines are prepared for their
first deployment. At Amsteg, two Hard Rock TBMs have successfully crossed a known fault zone by
applying full circle steel arches and shotcrete immediately behind the cutter head. Comparisons between
Drill & Blast and Hard Rock TBM are shown.
1 WHAT IS DIFFICULT GROUND?
Obviously there are many known definitions about what difficult ground is or may be. For the purpose of
this paper, difficult ground is defined as ground known or unknown in advance that requires an
alteration of the main, general driving method.
2 WHAT DOES RISK MANAGEMENT STAND FOR?
Risk Management (RM) is your best valuable tool to manage your uncertainties successfully.
Following a well-known and widely accepted method, using an interdisciplinary and inter-hierarchical
team under the leadership of an experienced risk manager, risk management enables you to
Identify all your relevant hazards,
Evaluate your risks by severity of damage and probability of occurrence,
Develop mitigating measures,
End up with system safety by using a safety system,
Transparently register all residual risks.
For further details please enjoy a closer look at some of the subject related literature in the bibliography at
the end of this paper and our published contributions for
North American Tunneling (NAT) Conference 2002: Integrated Management System
Published Paper (pdf - protected): http://www.moergeli.com/dldoc10e.htm
Presentation (ppt protected): http://www.moergeli.com/dldoc11e.htm
North American Tunneling (NAT) Conference 2004: Risk Management in Tunneling
Published Paper (pdf - protected): http://www.moergeli.com/dldoc21e.htm
Presentation (ppt protected): http://www.moergeli.com/dldoc22e.htm
TRANSCO Sedrun (ppt protected, German only): http://www.moergeli.com/dldoc11.htm.
3 HOW DOES RISK MANAGEMENT HELP YOU IN TUNNELING?
By strictly going through the full procedure step by step a/any Risk Management System (RMS) allows
you to early on and well in advance
Identify possibly difficult ground before actually facing it physically,
Choose the most suitable way of managing the grounds unexpected challenges (what tunnelers keep
calling real, hard-boiled tunneling), including reasonably unforeseeable ground performance
resulting from the interaction with your tunnel driving equipment,
Active risk management is not rocket science and it does not take a wizard! Just do it!
4 GOTTHARD BASE TUNNEL
4.1 General Project Overview
The Gotthard Base Tunnel (GBT) will become the worlds longest tunnel and has already been subject of
numerous publications. Please check the owners website http://www.alptransit.ch/pages/e/index.php.
TABLE 01 Selected Project Data of Gotthard Base Tunnel (GBT) Owner AlpTransit Gotthard AG (ATG, http://www.alptransit.ch) Purpose New high-speed railway Location In the heart of Switzerland, Cantons of Uri, Grisons + Tessin Total tunnel length 56.8 km (= ca. 35.3 US statute miles)
Lot 151, Tunnel Erstfeld Length 7.4 km Preparatory work Lot 252, Tunnel Amsteg Length 11.4 km Under construction Lot 360, Tunnel Sedrun Length 6.8 km Under construction Lot 452, Tunnel Faido Length 14.6 km Under construction
5 Main tunneling lots
Lot 554, Tunnel Bodio Length 16.6 km Under construction Forecast final costs Ca. CHF 7.634 billion * (ca. $ 6.362 billion **) Geotechnical Borings 15,996 m (Keller 2004) Forecast construction time 1996 ca. 2015 *** Authors mandates Safety + Health Engineer for all tunneling lots under construction
* Incl. Swiss VAT (Value Added Tax) ** 1 $ (USD = US Dollar) CHF 1.20 (Swiss Franc, 01/2005) *** According to current knowledge
FIGURE 01 GBT Drive Methods FIGURE 02 GBT, Current Status 12/15/04
Courtesy of ATG Courtesy of ATG (website)
4.2 Lot 360, Tunnel Sedrun
4.2.1 General Project Overview
For current information please visit the contractors website http://www.transco-sedrun.ch (so far in
German only) or the authors North American Tunneling Conference 2002 (NAT02) presentation
TABLE 02 Selected Additional Project Data of Lot 360, Tunnel Sedrun Location Canton of Grisons (GR) Total tunnel system Ca. 20 km (= ca. 12.4 US statute miles) Excavation cross section Ca. 69 m2 ( 135 m2 in squeezing ground) Construction method Drill & Blast at up to 6 faces simultaneously Contractor TRANSCO Sedrun (TRANSCO, http://www.transco-sedrun.ch) Contract value CHF 1.165 billion * ($ 0.971 billion **) Geotechnical Boring 5 Bore holes @ 5,602 m for Tavetscher Sub-Massif (Keller 2004) Forecast contract time 1996 ca. 2011 *** Authors mandate Safety + Health Engineer (2nd level support for local Safety Officer)
* Excl. Swiss VAT (Value Added Tax) ** 1 $ (USD = US Dollar) CHF 1.20 (Swiss Franc, 01/2005) *** According to current knowledge
FIGURE 03 Sedrun Tunnel System FIGURE 04 Sedrun, Current Status 12/15/04
Courtesy of ATG Courtesy of ATG (website)
4.2.2 How do You Cross the Tavetscher Sub-Massif?
The Tavetscher Sub-Massif represents the geologically trickiest section during the construction of the
GBT with squeezing rock.
Early on, the owner took some strategic decisions with regard to a pro-active Risk Management
Full-face excavation and full circle profile.
Combine the yielding principle with defined rigidity according to the grounds characteristic
Use steel ring arch lining immediately behind the face (up to 16 elements, set up to a minimum
spacing of only 0.33 m, TH profile, yielding from the largest possible diameter of about 13 m to 11 m
in the event of tunnel convergence).
Use shotcrete as well as radial and long face anchors.
Systematically monitor all deformations in real-time.
Establish, implement, keep current and document a comprehensive owners Risk Management
System (RMS) in all phases of the project. Require the consultants, site supervisors and main
construction contractors to run their own RMS, keep it updated and documented at least twice a year.
FIGURE 05 GBT Geological Profile FIGURE 06 Sedrun Geotechnical Investigation
Courtesy of ATG Courtesy of ATG
4.2.3 The Solution: Four Roadway Support Machines with High-Mechanized Back-up
Due to the large cross-section and the great amounts of excavation support devices such as steel arches,
anchors, wet shotcrete and concrete a persistent mechanization of excavation safety is necessary. All
supply and removal must support the work places, with the correct quantities at the correct time, using a
well thought-out logistics concept. At the same time it should provide climatically humanized work areas
by ventilation and cooling.
The concept, basically designed by the owner and its consulting engineers, and engineered by Rowa
Tunnelling Logistics AG (rowa, http://www.rowa-ag.ch), is based on a combination of installations,
construction equipment and construction machinery:
Roadway Support Machine (RSM, in German: Strecken-Ausbau-Maschine, SAM).
Heavy lift crane.
The RSM concept is being used in mining for a long time, but never in a scale up to the Sedrun
In cooperation with competent mining engineers from GTA Maschinensysteme GmbH (GTA,
http://www.gta-maschinensysteme.de), rowa has further developed the roadway support machine for the
Sedrun tunnel heading for the main tasks of
Steel arch installation in a safe and efficient manner.
Mechanized cutting of the heading face anchors out of the work baskets.
Sealing the face with shotcrete by spray robots from the work baskets.
Uncompromising mechanization increasing performance, productivity and safety in the same process.
FIGURE 07 Roadway Support Machine (RSM) FIGURE 08 Roadway Support Machine (RSM)
Courtesy of rowa Courtesy of rowa
The heading installation basically consists of
RSM with work-baskets,
A 20 ton heavy lift crane for supplying the work areas,
A suspension platform with installations for aeration, cooling, etc.,
An infrastructure train with supply installations,
The mucking-out system for loading the muck trains,
Construction equipment and machinery (LHD, jumbo drill, excavator, spray-mobile, etc.).