Conventional Tunnelling in Urban Areas - General face bolts etc.) Subdivision of cross section usually depends on ground conditions, size of excavation and surface settlements control

1/1/4747Conventional TunneConventional Tunnellling in Urban Areas ling in Urban Areas -- GeneralGeneral

The 3rd Training course TUNNELLING IN URBAN AREA

Prague, 4-5th May 2007

Conventional TunneConventional Tunnellling in Urban ling in Urban Areas Areas -- GeneralGeneral

Miloslav Miloslav FrankovskyFrankovsky, , TerraprojektTerraprojekt a.s., a.s., SlovakiaSlovakiaPeter Stefko, Skanska Peter Stefko, Skanska –– BS a.s., SlovakiaBS a.s., Slovakia

ITA - AITES WORLD TUNNEL CONGRESS 2007 PRAGUE

TRAINING MATERIAL PREPARED BY


5Conclusions Conclusions and and referencesreferences

ConventionalConventional tunnellingtunnelling

SpecialSpecial measuresmeasures duringduring tunneltunnel drivingdriving

IntroductionIntroduction

Waterproofing and finalWaterproofing and final lininglining

Index

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Conventional TunneConventional Tunnellling in Urban Areas ling in Urban Areas -- GeneralGeneral


Introduction

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Definition of conventional tunnelling:

Any method of underground construction exceptmethods using full profile TBM could beconsidered as conventional tunnelling

Representatives:

• New Austrian Tunelling Method (NATM)• Shotcrete Lining Method (SLM)• ADECO method• Prevault method



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Conventional tunnelling:

• Ground around the tunnel is considered to be loadbearing element

• Type and quantity of support elements is adjustedin combination with development of groundreaction

• Stability is confirmed by frequent monitoring ofground reactions mainly by deformationmeasurement

• Depending on the conditions the requirement ofstiff or light deformable support is identified



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Typical support elements:

• Shotcrete lining reinforced by steel mesh or steelfibres

• Rock anchors of various types (SN, frictional, selftapping etc.)

• Steel ribs or lattice girders• Special measures ahead of the face (pipe roofs,

forepoling, face bolts etc.)

Subdivision of cross section usually depends on ground conditions, size of excavation and surfacesettlements control



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11Hard rock conditions:

• Drill and blast excavation, partially mechanizedexcavation

• Subdivision into top heading and bench• Invert in case of poor rock conditions• Support classes framework defines advance

lengths, type and quantity of support elements• Waterproofing system from membrane and

drainage pipes on side of tunnel walls (umbrellasystem)

• Final lining from unreinforced or reinforcedconcrete



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11Soft ground conditions without special requirements:

• Without buildings on surface above tunnel• Mechanized excavation• Subdivision into top heading, bench and invert• Special measures (e.g. pipe roofs, temporary invert,

elephant foot)• Shorter length of advance• Waterproofing system from membrane and drainage

pipes on side of tunnel walls (umbrella system)• Final lining from reinforced concrete usually adjusted

for full load of overburden



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11Soft ground conditions with special requirements:

• Settlements on surface are to be restricted – urbanareas with buildings or communications

• Subdivision of cross section with rapid ring closure• Excavation of small sections of face with immediate

support• Short length of advance• Fully tanked lining system with or without membrane

without permanent drainage • Final lining from watertight reinforced concrete

designed for the full water pressure



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ExampleExample ofof tunnelling in poor rock conditions, Sitina tunnelling in poor rock conditions, Sitina tunnel, Slovakiatunnel, Slovakia



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ExampleExample ofof tunnelling in soft groundtunnelling in soft ground conditionsconditions withwithdeformationdeformation restriction, Sitina tunnel, Slovakiarestriction, Sitina tunnel, Slovakia


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11 Interrelationships of tunnel design philosophiesInterrelationships of tunnel design philosophies


SpecialSpecial measuresmeasures duringduring tunneltunnel drivingdriving

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11The choosen Special Measures should make provision for:

Engineering and geological conditions - usualy soft groundconditionsHydrogeological conditionsThickness of overburdenLocation and distance to built up areaRestrictions – noise, vibration, working hours etc.Requirements – deformation limitations, settlement controlmeasures The size and geometry of excavating profile


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11 TheThe selection and design of properselection and design of proper excavationexcavation sequencessequencesdepends on severaldepends on several parametersparameters:

• Size of tunnel

• Type of rock or soil

• Deformation limitations

• Vibration (blasting) limitations

• Equipment types and capacities

• Experience of contractor – client

• Construction time, schedule


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11 SprayedSprayed concreteconcrete liningslinings


SpecialSpecial measures measures –– division of excavation facedivision of excavation face

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Typical horizontal face division• Top heading – Bench – Invert (done with or without shotcrete)

Combination of horizontal and vertical face division• Top heading – vertical division with or without temporary invert

• Face division into sidewall or multiple drift technique

Special cases• Exploration gallery (location in profile)

• Excavation in very small steps with subsequent immediate instalation of at least a part of the support (ex. shotcrete sealing)


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Profile with quick ring closure Designed profile

Tunnel Lainz, Construction Lot 31, AustriaRailway link between western and southern railway line in Vienna, double

track railway tunnel. Length: 1.800 m, Cross Section 130 m².

ProfilesProfiles comparison comparison –– surfacesurface settlementsettlement reductionreduction


SpecialSpecial measures measures –– CentralCentral GalleryGallery

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Tunnel Valík, Czech RepublicMotorwayMotorway D5 D5 PrPragueague –– Norimberk, Norimberk, bypassbypass PPlzeňlzeň


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11 Excavation by single driftExcavation by single drift techniquetechnique

Cross section Longitudinal section

Plan Excavation sequence


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11 Excavation by multipleExcavation by multiple driftdrift techniquetechnique

Cross section Longitudinal section

Plan Excavation sequence


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11 ExcavationExcavation sequencesequence forfor escalatorescalator tunneltunnel

Vertical position of lattice girders


SpecialSpecial measures measures –– Driving and Main ConstructionDriving and Main Construction StagesStages

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Example – Underground Station

Excavation and support of crown of centre drift

Excavation and support of bench of centre drift

Construction of supportframes

Excavation and support of the two side drifts

Excavation and support of the two middle drifts

Lining construction


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11 ExcavationExcavation SequenceSequence usingusing pillarpillar driftsdrifts


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11 ExcavationExcavation SequenceSequence usingusing PillarPillar DriftsDrifts


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11 SpecialSpecial measures measures –– supportsupport elementselementsMost frequently used:

• Wire Mesh – additional layer• Shotcrete plain or reinforced - additional layer• Steel rib – reduced spacing, stronger profiles• Rock bolts – change type (expansion, fully embedded,

injection, self drilling etc.) and/or additional rock bolting

• Cable anchors• Forepoling pipes or bars• Lagging sheets, made from 3 – 4 mm steel sheets used

in cohesionless material


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11 SubsurfaceSubsurface measuresmeasures duringduring excavationexcavation

• Shotcrete sealing – temporary support• Supporting core• Face bolting• Forepoling• Ring closure• Strengthening - applying immediately (shotcrete, wire mesh, rock

bolts)• Shortening of length round – acc. actual conditions encountered up tu

0,8 – 0,6 m• Lagging sheets – auxiliary support (used in cohesionless material)• Lining stress controller LSC - yielding support (used in squeezing rock)• Compensation and permeate grouting


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11 SubsurfaceSubsurface measuresmeasures

Supporting core

Shotcrete sealing

Face bolting

Large anchor plates for betterload distribution


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Method Area of utilization

Description Plants & equipme

nt

Driven-inrebars

Strongly weathered ground,consistent non-cohesive soils

Steel bars for ex. Ø 25mm, length 2,5 to 6m, driven-inSteel pipes for ex. Ø 40mm, length 2,5 to 6m, driven-in

Drilled rebars

Slightly weathered ground

Steel bars for ex. Ø 25mm, length 2,5 to 6m-plugged-in to pre-drilled holes- plugged-in to pre-drilled holes filled with groutSteel pipes for ex. Ø 40mm, length 2,5 to 6m, plugged-in to pre-drilled holes filled with grout

Drilljumbo, groutpump

CrownCrown support support –– ForepolingForepoling withoutwithout groutinggrouting


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11 CrownCrown support support –– ForepolingForepoling withoutwithout groutinggrouting

Method Area of utilization

Description Plants & equipm.

Grouted driven-in rebars

grout able soilsand rocks

Threaded steel bars Ø 25, 32, 38mm with head adjustment for driving-in. Grouting from the rebar´s head

Grout pump

Self drilled rebars

non-cohesivesoils, unstable drilled holes

Threaded steel bars Ø 25, 32, 38mm with drilling bitGrouting via rebar´s head.Drilling bit is screwed onto rebar external threading

Drill jumbo, grout pump

Grouted pipe rebars

grout able soilsand rocksnon-cohesivesoils, unstable drilled holes

Threaded steel bars Ø 25, 32, 38mm with drilling bit. Grouting via rebar´s head with valve enabling secondary grouting. Drilling crown is screwed into pipe internal threading.

Drill jumbo, grout pump, pressure valve


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11 SubsurfaceSubsurface measures measures -- ForepolingForepoling1. Shotcrete sealing with or without

wire mesh2. Erection of steel rib3. Shotcrete to nominal thickness4. Forepoling pipes or bars5. Second layer of wire mesh and

shotcrete

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SpecialSpecial measures measures -- ForepolingForepoling

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Rock bolts, length 6m

Rock bolts, length 4m Forepoling bars, length 6m, ø 25mm

Top Heading

BenchInvert Top Heading min. 25m ahead

Max. depends on ground conditions


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11 CrownCrown support support –– ForepoledForepoled umbrella (pipeumbrella (pipe roofroof))Method Area of

utilizationDescription Plants &

equipmentPipe roof without grouting

soils and rocks hardly grout able up to non-grout able

Horizontal predrilling, steel pipes driving-in Ø60-200mm, length up to30mPipes inner concreting

Drill jumbo, driving equipment

Pipe roof with grouting

soils and rocks easily grout able up to non-grout able

Horizontal predrilling, iron pipes driving-in Ø60-200mm, length till30m

Drill jumbo, driving equipment, grouting unit

Pipe roof with Jet Grouting

heterogeneticsoils with various distribution ofgrains

Horizontal predrilling, high-pressure grouting simultaneouslyexecuted with pullingout drilling rod Ø 0,5m to 1,0m, length up to15m, overlap 3 to 5m

Drill jumbo, drilling platform, high-pressure equipment(pump, mixer, feeder), datamonitoring equipment


SpecialSpecial measures measures –– PipePipe RoofRoof

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Rock bolts, length 6m

Length up to 30m, overlap 3 - 5m

Pipe RoofAngle app. 120º

Top Heading

BenchInvert

Driving direction


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11 JetJet Grouting Grouting –– exampleexampleinjectioninjection length 9m, length 9m, ØØ 60cm60cm

Top Heading – sand

Bench – silt

Invert - sandAdditionallysprayedshotcrete

Minnimum shotcrete thickness 20 cm under Jet Grouting piles


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11 JetJet Grouting Grouting –– exampleexampleinjectioninjection length 9m, length 9m, ØØ 60cm60cm

Minimum shotcrete thickness 20 cm under jet grouting piles

Top Heading – sand

Bench – silt

Invert - sand


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11 TunnelTunnel settlementsettlement troughtrough

Key:Key:aa-- tunneltunnel excavatedexcavatedradiusradius

Smax Smax -- tunnel tunnel maximum settlementsmaximum settlements

i i -- distance to point of distance to point of inflexioninflexion


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11 CompensationCompensation groutinggrouting

StationStation constructed in Vienna constructed in Vienna (compensation(compensation grouting used to controlgrouting used to control settlementsettlement))


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11 Geotechnical MonitoringGeotechnical MonitoringInstrumentation and measurement programs are an integral

part of tunnelling especially with NATM.

The objectives of measurements may comprise thefollowing:

• Verification of the design assumptions including the design model and design parameters

• Adjustment of the construction methods, supportsystems, and supplementary measures to the actualground conditions

• Minimization of construction hazards• Prevention of harmful impact to the environment


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11 Geotechnical Monitoring Geotechnical Monitoring -- ParametersParameters

Considering the specific requirements and stages of construction the following fields with parameters must beobserved:

• Ground water• Ground deformation• Soil – structure interaction• Observation of environment (adjacent buildings and

structures)• Progress monitoring


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11 Geotechnical Monitoring in Urban AreasGeotechnical Monitoring in Urban Areas

• Survey of building conditions before start of construction

• Measurement of settlements and heave

• Horizontal displacement

• Tilt measurement

• Vibration due to blasting

• Noise due to blasting, ventilation etc.


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11 Geotechnical Monitoring in Urban AreasGeotechnical Monitoring in Urban AreasLocation of Tunnelling Face relative to Instrumentation Cross Section

Instrument Monitoring Frequency

InstrumentationCross Section

d


e

Surface settlement reference points

Extensometer

Inclinometer

Piezometer

d > 50m Initial reading

d < 30m Once a day

e < 30m Once a day

e > 30m Once a week


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11 Geotechnical Monitoring in Urban AreasGeotechnical Monitoring in Urban AreasLocation of Tunnelling Face relative to Instrumentation Cross Section

Instrument Monitoring Frequency


e InstrumentationCross Section

3D-Monitoring Pins

Pressure Cells (real time)

Initial reading immediately after installation at each subheading

e < 30m Once a day

e > 30m Once a week

Notes:The monitoring frequencies may be adjusted as requiredacc. to actual ground conditionsMonitoring frequency for real time pressure cells mustbe adjusted to the compensation grouting programme (if applied) as required


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11 Geotechnical ReportGeotechnical Report

Must include at least:

• Introduction

• Site information provided at the time of tender

• Ground conditions encountered during excavation

• Comparison between the expected and encountered ground conditions

• Conclusions



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Protection against groundwater – waterproofing

• Open (umbrella system) – waterproofing membranefrom PE or PVC protected with geotextile with pipedrainage (usually on sides of tunnel walls)

• Fully tanked system – waterproofing layer withoutpermanent pipe drainage in case when groundwaterlevel should not be affected by tunnel

• Double waterproofing divided into the sections by cross and longitudinal waterstop profiles especially fortunnels under groundwater level



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Final (secondary) lining

• Unreinforced concrete – usually for hard rock conditions and for vault shape and circular crosssections

• Reinforced concrete – for soft ground conditions, poor rock conditions and for special shape cross section (niches, laybies etc.)

• Reinforced watertight concrete with protection ofworking joints (e.g. waterstops) – for tunnels undergroundwater level



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ExampleExample ofof roadroad tunneltunnel withwithunreinforcedunreinforced finalfinal lining and openlining and openwaterproofingwaterproofing systemsystem withwith sidesidedrainagedrainage pipes (Branisko Tunnel, pipes (Branisko Tunnel, Slovakia)Slovakia)

ExampleExample ofof railrail tunneltunnel withwithreinforcedreinforced finalfinal lining (Zurich lining (Zurich --ThalwillThalwill Tunnel, Switzerland)Tunnel, Switzerland)



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• surface protection of lining using special plates• sufficient cover of steel reinforcement• polyprophylene fibres added to the concrete

mixture

Final lining from the fire protection point of view

Final lining is load – bearing element with permanentfunction. Fire in tunnel with very high temperaturescould cause collapse of lining. This could be verydangerous in case when buildings are situated abovethe tunnel.Various protective measures should be done for liningprotection:


Conclusions and references

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• Excavation stages must be sufficiently short, both in terms of dimensions and duration.

• Completion of primary support - in particular, closure of the shotcrete ring must not be delayed

Conventional tunnelling methods are widely usedvirtually in all types of ground conditions.The application of sprayed concrete primary support in soft ground tunnelling is relatively recent comparedwith its use in hard rock tunnelling. For tunnels in urban areas limiting settlements is of high importance to avoid damage to overlying structures. To achievethe essential limitation of settlement, the followingprincipal measures must be undertaken:

Documents

Conventional Tunnelling in Urban Areas - General face bolts etc.) Subdivision of cross section usually depends on ground conditions, size of excavation and surface settlements control