TBM IN SOFT GROUND

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejTBM IN SOFT GROUNDLecture: Eng. Marco Barbanti – Astaldi S.p.A.13.10.2011

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejEARTH PRESSURE BALANCE SHIELD 1. Tunnel face 2. Cutting wheel 3. Excavation chamber 4. Pressure bulkhead 5. Thrust cylinders 6. Screw conveyor 7. Segment erector 8. Segmental Lining

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejEPB PRINCIPLEThe face support is provided by the excavated ground that is kept under pressureinside the excavation chamber by balancing the volume of the extracted andexcavated material and by the thrust jacks on the shield.Excavation debris is removed from the excavation chamber by a screw conveyor thatallows the pressure control by variation of its rotation speed.increasing / debasing thrust forceincreasing / debasing advance ratewaterpressureearthpressure

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejEPB-SHIELD.FOUR MODI: OPEN TO CLOSED.slurryslurry modeclosed modeclosed(compressed air)modeopen modedecreasing face stabilitydecreasing water pressure

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejEPB-SHIELD.MODE: SLURRY / CLOSED.slurry

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejEPB-SHIELD.MODE: CLOSED (compressed air) / OPEN.

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejEPB-SHIELD: THE SCREW CONVEYOR

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejEPB-SHIELD: SCREW CONVEYOR

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejEPB-SHIELD.SCREW CONVEYOR. PRESSURE DISTIBUTION.3,00,52,7pressure screw conveyor inletearth pressure screw conveyor [bar]Erddruck Schneckenförderer [bar]2,42,11,81,51,20,90,60,3decreasing pressure per helixpressure screw conveyor outlet0,40,30,20,1decreasing pressure per helix [bar]Druckabbau pro Wendel [bar]0,00

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejSCREW CONVEYOR DETAILSGAUILLOTTINE – SAFETY GATEThe lower part of the bulkhead in the frontshield of an EPBS must be equipped with asafety gate, which can be closed when thescrew conveyor is retracted formaintenance. This allows the completeinsulation of the plenum, avoiding water/material inflow during maintenance.

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejEPB-SHIELD:APPLICATION RANGE AND CONDITIONING.claysiltsandgravelopen shieldpossiblecoarse soilfoam + polymersconditioning necessaryfoam and additives(clogging - adhesionof soil)silty sandfoamvery coarse soilfoam, polymersand fullersieve size [mm]

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejGEOTECHNICS: SOIL RECOMMENDATION

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejFOAM: CLOGGING-ADHESIONON STEEL SURFACE1,50Consistency Index I C1,401,301,201,101,000,900,800,700,600,500,40hardhardstiffstiffsoftpulpyMedium clogging riskLow clogging riskHigh clogging risk0,300 10 20 30 40 50 60 70Plasticity Index I P[%]

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejGEOTECHNICS.SOIL RECOMMENDATION.Soil recommendation for EPB-mode:cohesive and plasticsoft stiff consistencysmall inner angle of frictionlow permeability

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejCONDITIONING AND FOAM GENERATIONPressurebulkheadTensidewaterCutting wheelScrew conveyorAirWaterLiquidTensideAdditivePolymer

FOAM: PROPERTIESProperties of foaming:plasticshort term cohesionlower angle of frictionlower permeabilityDifferent foams have different:foaming capacitystabilityCourse in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejAnti-clay capacityAdvantages of foaming in softsoil:reduction of friction angle ofsoilshort term cohesion of soilplasticity and lowerpermeability of soillower wearlower torqueshort term stabilistation of facelower cloggingsoil structuringrheological impact (liquefaction / stiffening)drying-up capacity

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejFOAM: CONDITIONING IN SOFT SOILLow cohesive sandShort-term cohesion via foam

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejFOAM: FOAM INJECTION RATEfoamFoam Injection Rate (FIR):screw conveyorFIR regulates amount of foamFIR correlates with pore volumeFIR = volume foam / volume soilFIR correlates with advance ratebelt conveyor

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejFOAM:FOAM EXPANSION RATEAdditive (2 - 5%)Foam Expansion Rate (FER):FER regulates qualityWater (95 - 98%)FER 14:11 Liquidlow FER = wet foamhigh FER = dry foamFER = volume foam/volume liquid13 air

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejFOAM: CLOGGING,ANTI – CLAY – ADDITIVE.Use of Anti-clay-Additives in clay as well as in silt & sand:Problem- adhesion on steel surface- cohesion of greater clay lumpsConclusion- clogging of cutting wheel- clogging of screw conveyor or excavation chamber

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejFOAM CONTROL AND FOAM GENERATOR.Foam generatorAutomatic ModeSemi-Automatic Mode (FER)Manual Mode (FIR/FER)short distance totunnel face

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejEPB TBM vs. SLURRY TBM

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejTBM DESIGN CONSIDERATIONCRITERIA FOR SELECTION OF EPB OR SPBGeological conditionsGrain size distributionWater level and pressurePresence of boulders or obstructions along the alignmentAvailability of use of conditioning agents and /or bentoniteFeasibility and space for treatment plantFinal use and discharge of excavated muckExperience of contractorCapital cost

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejSIMILARITIES OF DESIGNThe basic design of an EP TBM and a SPB TBM are quite similar.The overall appearance and many systems from one type are useddirectly on the other.These similarities include:Main structuresPropulsionTrailing gantry StructureSegment Erector and handling

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejEPB vs. SLURRYEPB TBM•Overall simpler system to learn,operate and maintain•Applicable to a wider range ofgrounds•Requires limited addition ofconditioning materials (lowerconsumption of additives – noslurry circuit)• Incase of face collapse amountof ground loss is limitedSLURRY TBM•Overall a more complicatedsystem (to learn, operate andmaintain)•Applicable to a restricted range ofgrounds•Requires extensive addition ofmaterials• In case of face collapse amount ofground loss is considerable

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejEPB vs. SLURRYEPB TBM•Muck is immediately ready fordisposal•Able to take advantages ofselfsupporting grounds (i.e.open mode)•Higher overall production rates•Requires a limited space forassembly and launching•Low environment impactSLURRY TBM•Requires a sophisticated slurryseparation plant•Cannot take advantage ofselfsupportinggrounds (i.e. no open mode)•Advance rate of TBM directlyaffects all aspects of slurryperformance•Requires a large size job site

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejEPB vs. SLURRYEPB TBMSLURRY TBM•Lower capital cost•Required confinement pressuremust be calculated in advance oftunnelling•Requires higher torque•Requires greater Cuttingheadpower•High environmental impact•Higher capital costs•Required confinement pressure isdetected and controlled by thesystem•Requires lower torque•Requires less Cuttinghead Power

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejEPB vs. SLURRYEPB TBM•Muck is exposed into tunnel,contaminated grounds canpresent problems•Able to process a largerdiameter boulderSLURRY TBM•Contaminated muck is notexposed until it reaches thesurface•Requires a sophisticatedextraction system• Insulation of pipes from weather•Higher accuracy in pressureconfinement•Higher power requirement

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejEPB vs. SLURRYEPB TBMSLURRY TBM•High usage of energy on site, theslurry pumps must continuouslyfunction•Constant monitoring andadjustment of slurry parametersare required to achieve productionand muck removal requirements•Requires a overburden of at leastone TBM diameter as a minimum•Difficult to maintain slurry pressureat constant level when theextracting pipe clogs - up•Able to integrate rock crusher

CRITERIACourse in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejTYPE OF FACE SUPPORTEPBSLURRYCuttinghead Power/TorqueOverall site Power RequirementsUse of AdditivesCapitol CostRequired Site SizeDisposal excavated MaterialSpeed of ExcavationCleanliness of TunnelCalculation of Required PressureHighModerateRequiredLowModerateEasyFastPoorPredeterminedLowHighRequiredHighLargeComplexModerateGoodAutomatic

Course in Tunnelling and Tunnel Boring MachineKurs w zakresie drążenia tuneli oraz maszyny drążącejTHANK YOU FOR YOUR ATTENTION!!Eng. Marco Barbanti – Astaldi S.p.A.