tunnels concepts

TUNNELS

TERMINOLOGY for UNDERGROUNDSTRUCTURES

AditTunnelSubwayShaftChamberPortalPilot aditCentreFaceWall ~ siteFloorRoof

OverbreakExcavated profileNatural archlingLoadSupportFailureGentle failureRock burstSqueezing groundSwelling groundClay-filled jointLong term stabilityGround treatmentSupport before excavation

Jet grouted roof coverShotcrete initial liningJet grouted floor coverTop headingInvertBenchFinal concrete liningSHIELD tunnelling methodCUT & COVER tunnelling methodTBM (Full face ~ Total Boring Machine)

TERMINOLOGY for EXCAVATIONS ofROCKS & SOILS

DRILLINGHardnessToughnessAbrasivenessStructureDrilkling fluids

AUGERINGMACHINE BORING

Total Boring Machine (TBM)Full face excavation

BLASTING

SCRAPINGRIPPINGDIGGINGGROUND WATER

Control of groundwaterGroundwater flowRate of flowVolume of flowBoundaries

TUNNEL DESCRIPTION

1. Made into natural material (rocks)2. Empty inside3. Carry the loads itself4. Both ends are open to atmosphere5. Generally horizontal6. Thick walled structure looks like cylinder

1- Kilit (anahtar) ta ........................Key stone

2- Kemer...........................................Arch

3- Ayak (duvar)................................Wall

4- Taban...........................................Floor

5- Üzengi..........................................Bench

6- Üzengi çizgisi (düzeyi)...............Bench line or plane

7- Kalot............................................Top heading

8- Stros............................................Invert

9- Ano..............................................Ano (unit)

Tunnel Section for Swelling Ground

1- Digging section

2- Support

3- Swelling section

4- Pressurized area

5- Flow direction of water

SURFACE EXCAVATIONS

Deformation & failure

UNDERGROUND EXCAVATIONSIn RockIn Sediment

Stability & ArchingWater

Dry tunnel...............above water tableWet tunnel..............below water table

GasesCarbon dioxide (CO2)Carbon monoxide (CO)Methane (CH4)Hydrogen sulphide (H2S)Other gases

Gas bursts......................gaz patlamasRock falls........................kaya dü mesiRock bursts....................kaya f rlamasSqueezing ground.......... en – kabaran zeminTemperatureSubsidence

EXPLORATION & INVESTIGATIONSRELATED of SLOPE STABILITY

Geomorphologic maping and preparation oflongitudinal & cross sectionsGeological maping & surveyings (aerialphotographs)Geophysical surveyingsUnderground explorations, boreholesGround water surveyingsLaboratory testsModel studies

SURFACE EXCAVATIONS

PermanentShort term excavations

SUBSURFACE EXCAVATIONS

1. GEOLOGY1. Soil profile or hard rock geology2. Structure3. Ground water (hydrogeology)4. Stability

2. INVESTIGATIONS1. Mapping (Topographic, geologic, etc...)2. Geophysical surveying (especially seismic

velocity of rocks)3. Trial pits & boreholes4. General and local stability analysis5. Decide to excavation method

UNDERGROUND EXCAVATIONS

Adit, shaft, incline, large chamberTunnelSubway ~ metroUnderpassShelterPower houseWare house, store, mining ...etc

GASES(can be lethal or burst)

Carbon monoxide (CO) 0.97 of airCarbon dioxide (CO2) 1.53 of airMethane (CH4) 0.55 of air

(Highly explosive with air) marsh gas

Hydrogene sulphide (H2S) 1.19 of air(Highly toxic and explosive)

Sulphur dioxide (SO2)

ROCK FALL

SQUEEZING GROUND (sand, silt, shale, clay)

ROCK BURST

BULKING (Increase in volume, 10-40%)

FACTORS EFFECTINGEXCAVATION of ROCKS

Mineralogical composition of rocksTexture & fabricPetrographic featuresStructureRock massStrike & dip of beds in relation to face ofexcavationIntensity of tectonic disturbancesDegreee of weathering

RESISTANCE of ROCKS toEXCAVATION

Loose soilsSoil easy to spade (bel ile kazmak)Soil easy to digCrumbling weak rocks (ufalamak)Rocks easy to blastRocks difficult to blastRocks very difficult to blast

TUNNELLING METHODS

SHIELD TUNNELLING METHOD

This method involves the use of shield machine to drivethe tunnels below the ground.After completion of a work shaft, the shield machine islowered into the shaft and assembled there beforeexcavation and construction of the tunnels using precastconcrete lining segments of about 1.2 meter width.This construction method causes minimal disruption totraffic and the environment because all the work takesplace below ground and the ground level environment isunaffected.

CUT and COVER TUNNELLINGMETHOD

This construction method, whereby the site is fullyexcavated, the structure built and then covered over,uses diaphragm walls as temporary retaining walls withinthe site area.Step one :Construction of diaphragm walls, pin piles, anddecking.Step two :Excavation within the diaphragm walls,installing struts as work progresses.Step three :Construction of permanent floor slabs andwalls.Step four : Fitting out the internal structures, backfilling,and reinstating the surface structures.

TBM (Tunnel Boring Machine)

1. Mechanical-support TBM2. Compressed-air TBM3. Slurry shield TBM4. Earth pressure balance machine5. Mixed-face shield TBM

1- Mechanical Support TBM

A mechanical-support TBM has a full-facecutterhead which provides face support byconstantly pushing the excavated materialahead of the cutterhead against thesurrounding ground.

2- Compressed-Air TBM

A compressed-air TBM can have either afull-face cutterhead or excavating arms.Confinement is achieved by pressurizingthe air in the cutter chamber.

3- Slurry Shield TBM

A slurry shield TBM has a full-facecutterhead. Confinement is achieved bypressurizing boring fluid inside thecutterhead chamber.

4- Earth Pressure Balance Machine

An earth pressure balance machine has afull-face cutterhead. Confinement isachieved by pressurizing the excavatedmaterial in the cutterhead chamber.

5- Mix-Face Shield TBM

Mix-face shield TBMs have full-facecutterheads and can work inclosed oropen mode and with different confinementtechniques.

EFFECT of GEOLOGICAL STRUCTURESto TUNNEL EXCAVATION

Effect of soil layers: horizontal, vertical andinclined layers have different kinds of loadingconditions for tunnels.

Effect of faults: the relation between the faultslope direction and the tunnel direction, widthof the fault zone, type and thickness of the fillmaterial and the hydrostatic pressures in bothsides of the fault are some problems in thetunnelling.

Relation between the fault zone and the tunnel

Tunnel excavations in the slopes: thediscontinuities (layers, fissures) inclined insideor outside of the slope are very importantregarding the stress and strength of the tunnel.

Effect of the folds: While tunnel is excavated inan area that contains folded rocks, differentstresses and conditions may occur depending onthe fold type.

Fold axis and the tunnel direction is vertical

Fold axis and the tunnel direction is parallel

CLASSIFICATION ofROCKS for TUNNELING

PURPOSES

Classification of rocks for engineering purposesis needed in analyzing the project costs and toobtain an economic and reliable solution.

The classification of the rocks, that the tunnelwill be constructed in, is first done by Terzaghi.But, it is too general and gives qualitativeresults.

TUNNEL ROCK CLASSIFICATION by TERZAGHI

Laufer classified tunnel rocks to 7 groups according to stand-up time

Rock classification and determination of unsupported span

URFA IRRIGATIONTUNNEL

ONE of the LONGEST IRRIGATION TUNNELS inthe WORLD

Consist of two concrete lined tunnelseach of which is 7.62 m in diameter and

26.4 km in length discharging waterfrom the reservoir of Atatürk Dam.