rehbock kathmandu 2011 tbm workshop

TBM Tunnelling in the Himalayan Region, Kathmandu, Nepal, January 27, 2011

TBM TUNNELLING IN THE HIMALAYAN REGION

WORKSHOP KATHMANDU JANUARY 2011

Experiences in Long TBM and Drill & Blast Tunnels under Consideration of Risk Management Issues

presented by:

M.Sc. M. Rehbock-Sander

Amberg Engineering Ltd., Regensdorf, Switzerland


Introduction


Introduction

Challenges

Here at the Gotthard Basetunnel

Logistics via shafts and access tunnels


Sedrun shaft

Portal installationfield

Northern drives

Foot of shaft

Concrete plant, silos

Access tunnel

Pipeline for pneumatic cement conveying

Depth ~800 m

Trackbound transport

Counterweight

Gotthard Base Tunnel

Trackbound transport

Southern drives

Head of shaft

- carrying persons- excavated material

Cage for:

- construction material

Ventilation tunnel

Introduction


Introduction Main Challenges of Long and Deep Tunnels

Tunnel length leeds to long construction time

Automation of all procedures, trend to the use of TBM

Intermediate points of attack if possible

High overburden

Investigations

Not possible over the entire length

Higher remaining risks compared to other projects

Logistics

Long distances

Access shafts and galleries


Gotthard, Lötschberg and Vereina Tunnel, Switzerlandand Alborz Tunnel, Iran

Bern

Solothurn

Basel

Neuchâtel

Lausanne

Genève

Sion

Zermatt

Chur

St. Moritz

Bellinzona

Luzern

St. GallenZürichBaden

Schaffhausen

GBTGotthardBase Tunnel

LBTLötschberg Base Tunnel

F

D

F II

A

Lugano

Vereina


Technological ProgressTBM versus Drill and Blast

Clear tendency to the use of TBM in longer tunnels

On the other hand:

In Drill and Blast heading the possibilities to react to changing and difficult ground conditions are muchbigger

Drill and blast technology has developed and high advance rates are possible


Inrush of Water and Debris (Furka-Tunnel)


St. Bernadino Road Tunnel Vereina Tunnel

Technological Progress


Technological Progress


Vereina Tunnel, Back-up Installations

Suspended

back-upplatform


Lötschberg: Back- Up Installations, D&B Heading


Month

Contractor I Contractor II Contractor III Contractor IV

TBM

D&B

Gotthard, 12 km lot: Comparision of construction time


Offered Price Lot Faido, GBT

∆ 3 %

∆ 3 %

∆ 9 %∆ 0 %

Contractor I ContractorII

Contractor III Contractor IV

TBM

D&B

Gotthard, 12 km lot: Comparision of costs


Lötschberg Base Tunnel, length 34.6 km

(Source: www.bls.ch)


Lötschberg: Excavation Costs of TBM and D&B

0,7211520,-ET5a16090,-ESA5aV

1,037110,-No steelarches

0,687310,-ET4a10740,-ESA4aIV

0,945340,-ET3b5710,-ESA3bIII

0,894710,-ET3a5320,-ESA3a

1,183880,-ET23300,-ESA2II

1,223600,-ETA1a2960,-ESA1I

TBM / Drill&BlastCHF/mTBMCHF/mDrill & BlastSK


Lötschberg: Advance Rates of TBM and D&B

Minimum and maximum advancerates

0

5

10

15

20

25

30

35

PA 11 PA 12 PA 14 PA 15 PA 16 PA 18

m/d

ay

TBM max.TBM meanD&B max.D&B mean


1. Alborz Highway Tunnel, Iran

2. Gotthard Basetunnel, Railwaytunnel, Switzerland


Tehran Shomal Freeway

Total length: 121 km- Faster and safer connection- Reduction of fuel consumption

- largest structure: Alborz Tunnel- Length ~6‘300 m- Crossing the Elbrus Mountains

Alborz Tunnel, Overview


Alborz Tunnel Height: 2‘400 m strong winters


Alborz Tunnel, Overview


Alborz Tunnel, Investigations

Geoelectric survey + surface mapping

No drill holes

Service tunnel (diameter 5.4 m) = exploratory tunnel forthe main tunnels


Alborz Tunnel, Predicted Geology and HazardsHazards

Loose ground in fault zonesSwelling and karst in GypsumSqueezing in high overburdenUnknown water quantity, inrushGases: CH4 + H2S... others ...

GeologyComplex and heterogeneousFault zonesBig gypsum/anhydrite bodiesGypsum with massif karsticfeatures with unknownextend below surface


Alborz Tunnel: Open Gripper TBM

Service Tunnel

Open Gripper TBM

Short Shield

Anchors, steel arches and shotcrete directly behind cutter head


Alborz Tunnel, Exploration during Excavation


Alborz Tunnel, Exploration during Excavation: Seismic Prediction with TSP


Ingress of water (up to 1’000 l/s)

Alborz Tunnel, Challenges during Excavation


GasesMethane CH4 > explosiveHydrogen sulphide H2S > toxic and corrosiveCarbon monoxide CO > toxic



Excavation arround the TBM shieldto the front

- when cutter head or shield areblocked

- when they can not be releasedfrom inside or by other measures

Where:In crown or side wall ???

Bypasses


Bypasses

Blockage of Cutter head or Squeezing rock conditions

To free the TBM seven times bypasses had to be excavated mainly manually

Quick access to the face due to short shield



Bypass in crown pros and cons

Advantages:- in rather difficult conditions: better, more

chance for success- steel frames can use shield as foundation- no upward excavation required, crown

support can remain once installed- no interference with grippers, bypasscan be maintained together withTBM advance

Disadvantages:- for excavation down ahead of cutter

head: difficult mucking- eventually failures due to low horizontal

stress- more time consuming


Bypass measures ahead of cutter head


Open Gripper TBM was very flexible in difficult ground conditions

Excavation works were successfully completed. The contractor never used a TBM before

All described hazards and difficulties were overcome without anymajor accidents or even fatalities.

Average advance rate was almost 6.5 m/d

Improvement could have been achieved by better preparation for expected problems in advance in contrast to solving problems “on demand”

Alborz Tunnel, Conclusions


Gotthard Base Tunnel (GBT), Construction Sections

Total length: 57 km

Five construction sectionsErstfeld, Amsteg, Sedrun, Faido, Bodio

Three intermediate points of attack

Six heading directions


GBT, Tunnelsystem

access tunnelAmsteg

SedrunSedrunmultifunctionmultifunctionstationstation

shaft II

emergency stopstation

shaft I

shafts Sedrun

FaidoFaidomultifunctionmultifunctionstationstation

emergency stop station

access tunnel Faido

emergency stopin tunnel

fresh air, escape tube

waste air

single tracktube

150.4 km or 99 %

of access passages, shafts and maintunnels

have already been excavated


Gotthard Base Tunnel, TBM and Drill& Blast Sections

Drill and Blast


Range of Geological Risk 1992 and Accuracy of Cost Estimation +/- 25 %

Accuracy of Cost Astimation +/-25%


Investigations


Section Sedrun, Geological Investigation with Inclined Borings from the Surface


Tavetsch Intermediate Massif, Support Type SA4.4


Tavetsch Intermediate Massif, SedrunHeading in Squeezing Rock Conditions


Rock Support in Squeezing Rock Conditions

local 70 cm

Profil / Stahlbogen bei Tm 1171

Steel arches after installation

Steel arches after deformation

Acceptable deformation

AST 4.2


Excavation: 8.60 – 8.80 m Excavation: 9.20 – 13.08 m

Standard cross section Squeezing rock conditions (L > 1‘000 m !)

Cross Sections


Development of Deformations in TIM

Steel archeswith shotcreteapplication


Section Sedrun, Northern Tunnels

Full face excavation and installationof flexible steel arches with supportplacement rig

Radial Deformations up to 80 cm

Average advance rates of 90 cm/day


Piora Basin, Longitudinal Profile

Piora Basin: Triassic deposit of Dolomite in the Gotthard Massif, inserted between Lucomagno Gneiss and Medelser Granite


Piora Basin, Longitudinal Profile


Exploratory Gallery, Ingress of Water and Sugar Grained Dolomite, 31.03.1996

(Source: GBT, der längste Tunnel der Welt, Die Zukunft beginnt, Hrsg. R.E. Jeker Werd Verlag Zürich, 2002)


Exploratory Gallery, Ingress of Water

(GBT, der längste Tunnel der Welt, Die Zukunft beginnt, Hrsg. R.E. Jeker Werd Verlag Zürich, 2002)


Investigation of the Piora Basin

Piora - Basin

Profile parallel to GBT (Az N 346° E)

Gotthard - MassifLucomagno - gneiss

Medelsian - granite

Corandoni - zoneSolid dolomite todolomite marble

Lowest level of thegranular formation and thewater circulat ion

Quarten -serie

TriasRöti - serie

460.00Above sea level

500.00 a.s.l.

600.00 a.s.l.

700.00 a.s.l.


Kakirit

SSP

814.63Above sealevel

Projected

800.00

Lowest level of granular formationand the watercirculation

Gypsum cap

Sugar-grainDolomite

5 km long investigation gallery,

ingress of water,

wash in of TBM during investigation drillings

Investigation Drillings at GBT level:

solid Dolomite-Anhydrite formations

no water


Exploration - decision tree


Systematic exploration- Measure of temperature- Tunnel Seismic prediction- Percussion drilling- Protected with preventer

Depending on the results

excavation

Additional exploration- Borlog scanning- additional percussion drilling- Core drilling- Protected with preventer

Exploration - decision tree


Alborz Tunnel, Exploration during Excavation: Seismic Prediction with TSP


Piora Basin


Preventer:

Shear Preventer

Pipe Ram

Roto Pac

Piora Basin, Preventer


Piora Basin, Excavation


Range of Geological Risk 2000 and Accuracy of Cost Estimation +/- 10%

Accuracy of Cost Astimation +/-10%


Remaining Risks

More than 100 fault zones predicted

Deformations in TBM sections predicted (yielding support types necessary)

Squeezing ground conditions

Water inrush

Rock burst in D&B an TBM sections

Face stability



Remaining Risks countermeasures

Risk management process establishedFlexible rock support means and additional measures must be possibleInvestigations ahead of tunnel face necessary

Probe drilings, preventer protectedTSP

Open Gripper TBM was choosenDetailed prediction of intensity of hazards and necessary rock support and counter measures based on the geological predictionDetailed action plans for the existing hazards including all contractualaspects were prepared as auxiliary



Detaching of small blocks

Face instabilityPlastic deformationsRock burst

Wedges in the roofLoosening in the roof

[km]

500

3'000 m abore sea level

2'500

2'000

1'500

1'000

N

?+132

132

Borel-Zone

?

?

130 131

Tenelin-Zone

+++

+

? +130

+

+ +

++

+

+

++

?

++

+

Stripe gneiss

131

Stripe gneiss

?

62c

?

133

?

?

?

?

+?

+

?

++

++

?

+++

++ + +

+ +

+++

+++

+

++

?

? 1908?

+++

+

+

+++

++

+

+?

+

+

?

+

+

?

+

? ?

?

Water

S

Brittle failures

Hazards

\folie

n\am

berg

\gbt

-041

e.d w

g

Low intensity Medium intensity High intensity Extreme intensity

Ove

rbur

den

ca. 2

'000

m

Gotthard: Hazard Type and Intensity

Tunnel cross section

L = 3.0-4.0 m

ø 9.20

Bolt's grid1.5 x 1.5 m

14 Rock bolt

mesh supportSmal bolt for

Detail section L1*

Rock bolt

Wire mesh

10 cm Shotcrete

Wire mesh

10 cm Shotcrete

Detail section L2*

Tunnel longitudinal section

~ 20 m Section L1

L1*

Section L2

L2*

Gotthard: Rock Support Type FT5B/V


Gotthard: Distribution of Rock Support Types

0 % 5-10 % 11-20 % 21-30 % 31-40 % 41-50 %

[km] 132130 131

Detaching of small blocks

Face instabilityPlastic deformationsRock burst

Wedges in the roofLoosening in the roof

Water

Brittle failures

Hazards

Excavation support

FT 35 cm

Cast lining

7FT 6B 35 cmFT 6A 35 cmFT 5B 30 cmFT 5A 30 cmFT 4B 30 cmFT 4A 30 cmFT 3B 30 cmFT 3A 30 cmFT 2 30 cmFT 1 30 cmFT 0 30 cm

Support types

133

Low intensity Medium intensity High intensity Extreme intensity

Incr

easi

ng s

uppo

rt


Auxiliary Measure: Injection Gallery beside Tunnel Axis

Fault zone

Borings

Injection gallery

Excavation planned Alreadyexcavated


Auxiliary Measure: Injection Gallery beside Tunnel Axis, Intent: Improvement of Rock Conditions


Auxiliary Measure: Injection Gallery in Tunnel Axis, Intent: Improvement of Rock Conditions


Auxiliary Measure :Crown Gallery, Intent: Improvement of Rock Conditions


Auxiliary Measure: Top Heading, Intent: Supporting Vault


Auxiliary Measure: Access to TBM with Side Gallery


Action Plan Injections


Action Plan Spiles (15 m)


Gotthard: Sueezing Ground conditionsDestroyed Steel Arches


Principle of support in TBM Heading

L * L *1 2

ur

pa

DeformationDeformation

Support pressureSupport pressure

Resistance PrincipleResistance PrincipleYielding principleYielding principle


Vereina Tunnel, Steel Arch Setting


Steel Arches/horizontal Slots in Shotcrete Lining

Gottard Base-Tunnel


TH - Steel Arches, Yielding Support at the GotthardBeforeDeformation

After Deformation


Yielding Elements

Yielding elements before and after loading


TBM Switching by Low-Loading Truck


Increasingdiameter: 8.83 m > 9.43 m

TBM Assembly East Tube


Vereina Tunnel, Advance Rates Open TBM

692

0

100

200

300

400

500

600

700

800

Mai

95

Jun

95

Jul 9

5

Aug

95

Sep

95

Okt

95

Nov

95

Dez

95

Jan

96

Feb

96

Mrz

96

Apr

96

Mai

96

Jun

96

Jul 9

6

Aug

96

Sep

96

Okt

96

Nov

96

Dez

96

Jan

97

Feb

97

Mrz

97

Monat

Lfm

/Mon

at

Stö

rzon

e Tm

3'4

15

Die durchschnittliche Vortriebsleistung betrug 15.17 m/AT

month

m/m

onth

Steel Arch Support, Lot T4b


Yielding Steel Arches


- Rock support measures behind cutter head required

- Second possibility only 65 m behind the face

East tube

8-16 rock bolts

Steel arches every 100 cm

15 cm shotcrete

Mean advance about 6.5 m/day

Tunnel Faido, Rock Support Concept


Hazard Scenarios

TBM clambed in Fault zones


Hazard Scenarios

Rock burst


Hazard Scenarios

Damages of rock support due to deformations of the cross section


Gotthard Basetunnel: Breakthrough of the 57 km long tunnel


Advance rates in Drill and Blast Headings have increased in the last 10 yearsStill Drill and Blast gives more flexibility in difficult ground conditionsOpen gripper TBM have successfully been used also in squeezing ground conditions High demand of experienced staff for open gripper TBM (interpretation of geology, define necessary rock support, shotcreteing, logistics)All pieces within the puzzle of geology, TBM, logistics, have to fit

Conclusions


Detailed investigations over the entire tunnel length are impossibleConcentration of investigations on major risks is necessaryRisk management processDuring excavation additional investigations from the tunnel face are necessary Flexible Heading equipment is requiredDetailed preparation of counter measures for possible hazardsFair contract and Risk allocation

Conclusions


Thank you very much foryour kind attention!

Thank you very much foryour kind attention!

rehbock kathmandu 2011 tbm workshop

Documents