prepared by example ita/aitesmaboushook.kau.edu.sa/files/0053019/files/7097_421-4-btm.pdf · the...

TheThe exampleexample of Alp of Alp TransitTransit ProjectProjectLoetschberg base tunnelLoetschberg base tunnel

ITA/AITES ITA/AITES –– Training Training CourseCourseTUNNEL ENGINEERING TUNNEL ENGINEERING

ITA/AITESITA/AITES

May 6, 2005 11//4040

Prepared by Prepared by ““F.F. VuilleumierVuilleumier and G.and G. SeingreSeingre””

Istanbul Istanbul -- 20052005

5Conclusions Conclusions and and referencesreferences

Chapter 1 :Chapter 1 : Rockburst by TBM excavation

Chapter 2 : Chapter 2 : Face instability with block formation

IntroductionIntroduction : : Loetschberg-Base-Tunnel

ChapterChapter 3 : 3 : On site comparison between TBM and drill-and-blast

Index

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Introduction

Loetschberg-Base-Tunnelshort presentation

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Switzerland builds now 2 new alpine base tunnels

• GothardL = 57 km2015

• LoetschbergL = 34.7 km2007connection withSimplon-tunnel


Functions of the new rail alpine routes

• Integration of Switzerland in european high-speed railway network

• Transfer of alpine freight traffic from road to rail


Loetschberg - Project overview

- Length : 34,7 km- 2 tubes, 65-70 m2

- Total length of all galeries : 88 km

- Altitude max. : 828 m- Construction period :

1995 - 2006- Coming into operation :

2007


Geology


Construction concept

• 10 simultaneous tunnel drives

• Reducing time construction

• Risk management : max. length 10 km


Construction concept : D + B


Construction concept : TBM


Overall construction programme


Chapter 1

Spalling during TBM excavation

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Condition for stress-driven spalling

• Massive Rockmass• Brittle rock• High stress level

(high overburden)• Low confinement

(ratio σ3 / σ1)• Crack damage

initiationσtan max = 0. 3…0.5 σc

Doc. Diederichs

1313//4040The example of Alp Transit ProjectThe example of Alp Transit Project

Stresses on tunnel walls

• Kirsch (1898)• σr = 0• σtan max = 3 σ1 - σ3

• σtan min = 3 σ3 - σ1

- Doc. Hoek, Kaiser and Bawden


Spalling : stresses orientation

Loestchberg TBM drives• overburden up to

1700 m• σv~ σ1 > σh

• max. stresses on the tunnel wall

- Doc. Martin, Kaiser and Mc Creath


Stress-driven spalling : example


Problem for TBMGripper pads cannot

be seated on the side wall


Problem for TBM excavation

the 4 m TBM shield protects the workers


Support choice by spalling

Spalling• Standard support :

– Swellex-Bolts– Wire mesh (TBM)– Fiber-shotcrete (D+B)

• Bolts on tunnel wall (and on tunnel face by drill-and-blast)

Rockburst• Stored Energy => support

– Yiellding-Swellex orSplitset-Bolts

– Fiber-shotcrete or wire mesh and shotcrete

• High density of bolts on tunnel wall (and on tunnel face by drill- and-blast)


Support choice by spallingLearning from the first drive


Chapter 2

Face instability with block formation

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Face instability with block formation


Block formation before cutter head

Doc. ARGEMaTrans, TBM drive Raron

Damage at :-Mucking buckets-Disc-cutters-Band-conveyors

Abrasion of cutter-head


Face instability with blocks formation

• Claim of the contractor

• Influence of stress level and orientation

• Influence of tunnel radius (Kaiser)

• Influence ofschistosity and fractures


Chapter 3

On site comparison between TBM and drill-

and-blast

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Choice between TBM – D+B

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First difficulty : Trias zone Raron

•• 10 km OK 10 km OK forfor TBM TBM

•• 150 m Trias 150 m Trias zone too zone too difficult fordifficult for TBMTBM



>> small exploratory small exploratory gallerygallery onon western western tunneltunnel

>170 m >170 m conventionnal conventionnal prepre--excavationexcavation ofofeasterneastern tubetube


Choice of excavation’s type

PoliticsPolitics

•• Steg Steg drive readydrive ready to to gogoin 2000in 2000

•• Raron drive ready onlyRaron drive ready onlyin 2001in 2001

> TBM > TBM forfor Steg lateral Steg lateral aditadit


Other reasons• too short for economic

TBM excavation

• limited place at Portal Raron

=> east tunnel : TBM west tunnel : D + B

Choice of excavation’s type


On site comparison between TBM and drill-and-blast

Length 3‘400 m


� Lias-limestone, 750 m (22%)� Dogger (Aalenian) - marlschist

and limestone, 850 m (25%)� Quinten (Malm) - hard limestone,

470 m (14%)� Granodiorite, 780 m (23%)� Central Aar-Granite, 570 m

(17%)

Comparison of advance rates

Rock Type TBM (m/d) D+B (m/d)

Lias 6.5 5.6

Dogger (Aalenian) 17.8 7.3

Quinten Limestone 18.5 10

Granodiorite 22.2 8.7

Granite 13.7 10.2

unstableunstable layer in crownlayer in crown

very abrasive rock very abrasive rock and blocksand blocks


Lias limestone : unstable layer in crown

• Very schistose• Flatly dipping in the

direction of tunnel drive

• Convergence until 60 cm in TBM drive

• Few problems for drill and blast drive (unstable layer fell during blasting)


Central Aar granite : abrasivity and blocks

• TBM-head had to be repaired 4 times

• Protection of disc-cutters against blocks


Central Aar granite : abrasivity and blocks


Conclusions and references

• Hard rock TBM can drive under moderate spalling conditions=> orientation of grippers ?

• Stress-driven block formation can occur at TBM face under high overburden

• Orientation of schistosity and fractures

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ITA/AITESITA/AITES

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