Risk Management in Action – Controlling Difficult Ground by Innovation

A. Moergeli moergeli + moergeli consulting engineering, CH-8716 Schmerikon/Switzerland mailto:info@moergeli.com, http://www.moergeli.com

ABSTRACT: The Swiss are currently building the world’s 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 ground’s 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 world’s longest tunnel and has already been subject of

numerous publications. Please check the owner’s 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 *** Author’s 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 contractor’s website http://www.transco-sedrun.ch (so far in

German only) or the author’s North American Tunneling Conference 2002 (NAT02) presentation

http://www.moergeli.com/dldoc11e.htm.

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 *** Author’s 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 ground’s characteristic

pressure-support-behavior.

• 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 owner’s 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.

• Suspension rails.

• Suspended platform.

• Infrastructure train.

The RSM concept is being used in mining for a long time, but never in a scale up to the Sedrun

dimensions.

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,

• Shift arms,

• Spray robots,

• 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.).

The „Suspended Installation“ concept was selected for the following main reasons

• Creation of two work levels.

• Economic direct supply of work areas through a suspended heavy lift crane.

• Performance and safety (“Killing two birds with one stone”).

(Jenni 2004)

FIGURE 09 Steel Arch Setting by RSM FIGURE 10 Steel Arch Setting by RSM

Courtesy of rowa Courtesy of rowa

4.2.4 Outlook

All four Roadway Support Machines (RSM) are still awaiting their first deployment at the time of

finishing this paper (January 11, 2005). It is planned to

• Bring the two northbound RSMs to the faces and begin the special drives on February 2005.

• Convert the two southbound RSMs to high speed tunneling mode (de-installing the steel setting

equipment, adding on a crusher, adjusting the back-up logistics) in order to drive through the Urseren-

Garvera-Zone.

An update on the current RSM’s performance and the project status can be offered through a presentation

at the RETC 2005 Conference.

4.3 Lot 252, Tunnel Amsteg

4.3.1 General Project Overview

For current information please visit the contractor’s website http://www.agn-amsteg.ch (so far in German

only) or the author’s North American Tunneling Conference 2002 (NAT02) presentation

http://www.moergeli.com/dldoc11e.htm.

TABLE 03 Selected Additional Project Data of Lot 252, Tunnel Amsteg Location Canton of Uri (UR) Total tunnel system Ca. 26 km (= ca. 16.2 US statute miles) Excavation cross section Ca. 71.6 m2 (9.55 m TBM excavation diameter) Construction method 2 TBMs/Back-up trailers Contractor Joint Venture Gotthard Nord (AGN, http://www.agn-amsteg.ch) Contract value CHF 0.627 billion * ($ 0.523 billion **) Geotechnical Boring 2 Bore holes @ 340 m + data from a nearby head race tunnel (Keller 2004) Forecast contract time 2002 – ca. 2009 *** Author’s 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 11 Amsteg Tunnel System FIGURE 12 Amsteg, Current Status 12/15/04

Courtesy of ATG Courtesy of ATG (website)

4.3.2 How do You Cross the Intschi Fault Zone?

The Intschi Fault Zone has been well identified and documented since a long time ago.

The big question was, where/when and for how long the fault zone would be encountered. And, of course,

how it would perform under a TBM full-face excavation. ATG was prepared for a planned stop and

special ground treatment measures.

As it turned out, instead of 950 m, the fault zone finally lasted for about 440 m only (Keller 2004) and

had much less negative impacts on advance rates, as well as schedule, than originally expected.

4.3.3 Solution 1 in the East Tunnel: Additional Shotcrete Support in Gripper Areas

Coping with substantial TBM off-course deviation, strong convergences, re-profiling for the invert

concrete slab, hazardous working conditions etc., a different plan of action had to be formulated for the

lagging behind West Tunnel.

FIGURE 13 Intschi Fault East FIGURE 14 TBM Performance Intschi Fault East (February 2004)

Courtesy of AGN (website) Courtesy of AGN (Translation by author)

4.3.4 Solution 2 in the West Tunnel: Full Circle Steel Arches behind the Cutter Head

Setting full round steel arches right behind the cutter head from the beginning, a higher performance, no

TBM off-course deviation and safer working conditions resulted.

FIGURE 15 Intschi Fault West FIGURE 16 TBM Performance Intschi Fault West (May 2004)

Picture by author Courtesy of AGN (Translation by author)

5 COMPARISONS BETWEEN DRILL & BLAST AND TBM

The current controlling of difficult ground at the GBT proves once more that

• Technology development in the tunneling industry remains very active and innovative.

• Nearly any ground can be mastered when everyone within the chain of production is well prepared.

• Knowing, as precisely as possible and well in advance, where and when difficult ground will be

encountered, is a critical success factor.

• Quantum leaps both in construction performance as well as crew’s safety + health are within reach.

In our high-tech Drill & Blast (D & B) environment

• There is more freedom for real-time response.

• There is a need for more crew knowledge and experience based decision-making at the face.

• Site installations are commissioned faster and cost less.

Modern tunnel boring machines with their impressive industrialized back-up logistics are

• Advancing faster, while needing a lot more time to be commissioned.

• Providing safer workplaces.

• Much more susceptible to a perfectly working supply chain.

• Less flexible when running into any kind of difficulties.

• Requiring a much more expensive initial capital investment.

6 LESSONS LEARNT

While the exact location, length, status and strength of (difficult) ground may always remain a hidden

secret up to the very last moment, there is obviously never such a thing as enough geotechnical

investigation. Considerably time-consuming and (very) expensive (at least for such high overburdens like

at the GBT), however, cored drillings remain effectively your very best investment into the successful

management of difficult ground.

The chosen procedure was successful so far and there was a remarkable learning curve. Geotechnical

assessment is crucial for a successful realization of deep underground structures. A comprehensive

exploratory program is a must and decisions of where, how much and subsequent interpretations are

critical success factors. The choice of driving concept and installations has to match carefully the

knowledge taken out from the geotechnical investigation. Close cooperation between geotechnical

engineers and tunnel contractors, as well as an international experience exchange for deep tunnels, are

contributing to geotechnical assessment and are a prerequisite for risk management in tunneling. By

improving this factor, substantial advantages in technology, schedules and cost reductions can be realized.

(Vogel 2005)

FIGURE 17 Investment GBT FIGURE 18 Additional Investments

Courtesy of ATG (website) Courtesy of ATG (website)

There are not many things that you can rely on in tunneling. But there will always be unforeseen ground

waiting for you out there to run into – and certainly at your most un-welcomed moment! Sometimes it

may turn out to perform better, sometimes worse, than previously anticipated. Please be prepared for both

scenarios.

You may learn from ATG and its partners as well as from other projects, just keep your Risk

Management running, current and documented.

Although your project may differ in size and substance, Risk Management is truly generic. And you are

not alone, we are here to assist you. All our tools are available for download on

http://www.moergeli.com.

Risk Management is not rocket science and it does not take a wizard!

Just get it started – and keep it going and current.

Take care and stay safe!

We need all of you to shape a safer and more economic world! Thank you.

7 ACKNOWLEGEMENTS

The author thanks and acknowledges the very competent support and kind provision of plans, schemes

and pictures by:

FIGURE 19 AlpTransit Gotthard AG (ATG) FIGURE 20 TRANSCO Sedrun (TRANSCO)

FIGURE 21 Joint Venture AMSTEG (AGN) FIGURE 22 Herrenknecht AG (HK)

FIGURE 23 Rowa Tunnelling Logistics AG (rowa) FIGURE 24 GTA Maschinensysteme GmbH

Last but not least, my thanks goes to Mrs. S. Tschupp for her always very competent support in

improving my use of the English language. Without the big help of all of you, this document would not

have been possible. But the biggest thanks goes always to all crews on site, safely coping with the

unforeseeable as their daily routine. Every day they move into places, where no human being has ever

been before. Always just one small step for a man, but a giant leap for mankind ... The author’s apologies

go to the readers for any inconvenience dealing with small print, reduced tables and pictures. An update

f the paper can be offered through our presentation at the RETC 2005 Conference. The original paper

will be available on http://www.moergeli.com/dldocuebersichte.htm

o

shortly after the Conference.

8

17.06.2004, nd 3, p. 19

(http://www.sia.ch

REFERENCES

Keller, F. 2004, “AlpTransit-Tagung 2004”, Fachgruppe für Untertagebau (FGU), Schweizerischer Ingenieur- und Architektenverein (sia) Dokumentation D 0202, Ba

) Jenni, H. 2004, “Rowa Customers Day”, 07. September 2004, Sedrun/Switzerland, “Highly Mechanized

Heading Installation for Full-Face Excavation …” (http://www.rowa-ag.ch) Insurance Fund (suva, http://www.suva.chVogel, M. 2005, Swiss National Accident ), email

Alp lptransit.ch

9 FOR FURTHER INFORMATION

Transit Gotthard AG (ATG), Zentralstrasse 5, CH-6003 Luzern/Switzerland, http://www.aA. Moergeli, moergeli + moergeli consulting engineering, Rosengartenstrasse 28, CH-8716

Schmerikon/Switzerland, http://www.moergeli.com“Geologic Site Investigations for Tunnels”, USNC/TT Study, Eugene B. Waggoner, Charles

Daugherty, Underground Space, Vol. 9, 1985, pp. 109 – 119 W.

http://www.nap.edu/openbook/POD230/html/index.html (online-Version + pdf sum“Geotechnical Baseline Reports for Underground Construction, Guidelines and Practic

mary) es”, Randall J.

.gta-Essex, American Society of Civil Engineers, 1997, ISBN 0-7844-0249-3

GTA Maschinensysteme GmbH, Loikumer Rott 23, D-46499 Hamminkeln, http://wwwmaschinensysteme.de

Herrenknecht AG Tunneling Systems, Schlehenweg 2, D-77963 Schwanau/Germany, http://www.herrenknecht.de

Joint Venture Amsteg, Lot 252, Gotthard Base Tunnel North (AGN), Grund, CH-6474 Amsteg/Switzerland, http://www.agn-amsteg.ch

Joint Venture TRANSCO Sedrun, P.O. Box 67, CH-7188 Sedrun/Switzerland, http://www.transco-Sedrun.ch

Ro Wangen SZ/Switzerland, http://www.rowa-ag.chwa Tunnelling Logistics AG, Leuholz 15, CH-8855suva, Swiss National Accident Insurance Fund, CH-6002 Luzern/Switzerland, http://www.suva.ch“System Safety Scrapbook”, P. L. Clemens, 2002, Sverdrup Technology, Inc., http://www.sverdrup.comUS Military Standard 882D, 10 February 2000, US Department of Defense,

http://www.reliasoft.org/mil_std/mil_std_882d.pdf