Professor Jian ZHAO EPFL ENAC LMR TOS Laboratoire de ... 2011...EPB and slurry machines Hybrid Shield ... provide pressure support to the excavation face. Excavated materials can be

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Tunnel Boring Machines (TBM) – an introduction

Professor Jian ZHAOEPFL−ENAC−LMR

Laboratoire de Mécanique des Roches − LMR Tunnelling 1

Conventional and TBM Tunnelling

TBM Tunnelling

Laboratoire de Mécanique des Roches − LMR Tunnelling

Conventional Tunnelling

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TBM

Length

D&

B

Tunnelling and Use of TBM in

Switzerland

Laboratoire de Mécanique des Roches − LMR

TBM

Volume

D&

B


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Mechanical Face Support

Open Face

Compressed Air Shield

Weak, soft rock Firm soil

Weathered, highlyfractured rock

Firm soil withgroundwater

Rock mixed with soilShield TBM

Gripper TBM

Roadheader

Reaming Machine

Non-Shield TBM

Competent rock

Competent rock

Competent rock

Firm soil

Digger Impact breaker, ripper, pick, and bucket for weak weathered rock and firm soilBoom Excavator

Rock TBM

Earth Pressure Balance Shield

Air Shield

Slurry / Hydro-Shield

Soft clayRock mixed with soil

groundwater

Loose sandysoil

Rock mixed with soil

Soil TBM

Double Shield Ground from competent rock to soil


EPB-Slurry Convertible

Varying ground conditions suitable for EPB and slurry machines

Hybrid Shield

Mix-Shield Mixed ground conditions of rock and soil

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Basic Functions

1. Excavation of the ground

Partial Face excavation Full Face excavation


Basic Functions

2. Support the ground


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Basic Functions

3. Mucking of Excavated Materials


Advantages and Risks

ADVANTAGES

Enhanced health and safety conditions for the workers.Industrialization of the tunnelling process, with ensuing reductions in cost and

RISKS

Lack of flexibility: Once the technique has been chosen it is virtually impossible to change it throughout the construction of the tunnel.


construction times.Possibility of crossing complex geological and hydrogeological conditions safely and economically.Good quality of finished product (surrounding ground less altered, precast segment lining).

Therefore, a correct analysis of different parameters is needed for the choice of the correct mechanized tunnelling technique

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Open Face






Gripper TBM

Roadheader

Reaming Machine

Non-Shield TBM

Competent rock

Competent rock

Competent rock

Firm soil




Air Shield



groundwater

Loose sandysoil





Hybrid Shield


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Roadheaders and Mobile Excavators

Rock excavation machine for moderate rock strength (up to 120 MPa), consisting of:

• Cutterhead

• Extension arm or


Extension arm or boom

• Muck conveyor

• Crawler chassis

• Loading apron

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Roadheaders and Mobile Excavators

Mobile Miner


Continuous Mining Machine

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Roadheaders

ADVANTAGES

Flexibility.Possibility of excavating tunnels of different sizes and shapes.Low capital investment

LIMITATIONS

No protection or support given to the rock while excavating. Limited to stable ground.Suitable to excavate rocks of UCS up to 120 MPa.


Low capital investment.No installation time needed.Relatively short time from order to delivery at the site.

Excavation coverage is limited by the size of the machine.

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Open Face




Shield TBM

Gripper TBM

Roadheader

Reaming Machine

Non-Shield TBM

Competent rock

Competent rock

Competent rock

Firm soil






Air Shield





Hybrid Shield



groundwater

Loose sandysoil


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Tunnel Reaming and Enlarge Machines

Reaming boring machine bores the final section from an axial pilot tunnel from which it pulls itself forward by means of a gripper unit.

Laboratoire de Mécanique des Roches − LMR Tunnelling14


Tunnel Bore Extender (TBE) used at Uetliberg Tunnel in Switzerland. Tunnel is enlarged from a 5 m pilot tunnel to 14.4 m.

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Open Face




Shield TBM

Gripper TBM

Roadheader

Reaming Machine

Non-Shield TBM

Competent rock

Competent rock

Competent rock

Firm soil






Air Shield





Hybrid Shield



groundwater

Loose sandysoil


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Gripper TBM

Rock excavation machine for competent and hard rocks. Movement of machine uses the grippers.


Gripper

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Double gripper TBM


Rock is fragmented by chipping between cutters.

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Gripper TBM

Single gripper TBM MOVIE


g g pp

Double gripper TBM

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ADVANTAGES

Rapid excavation rate in hard rocks.Capable to excavate hard rocks of UCS up to 300 MPa.For tunnels of diameter up to

LIMITATIONS

No protection or support given to the rock while excavating. Limited to stable ground.Gripper may have difficult in poor rock masses with low

Gripper TBM


For tunnels of diameter up to 14 m.Flexible rock support measure according to ground conditions.

strength.Dedusting is needed.

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Open Face




Shield TBM

Gripper TBM

Roadheader

Reaming Machine

Non-Shield TBM

Competent rock

Competent rock

Competent rock

Firm soil






Air Shield





Hybrid Shield



groundwater

Loose sandysoil


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Open Face Shield and TBMOpen Face Shield


Open Face Platform ShieldOpen Face Tunnelling Shield

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Open Face




Shield TBM

Gripper TBM

Roadheader

Reaming Machine

Non-Shield TBM

Competent rock

Competent rock

Competent rock

Firm soil






Air Shield





Hybrid Shield



groundwater

Loose sandysoil


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TBM with Mechanical Face Support

Open face TBM can be for rock and firm soil without the need of face pressure.


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It usually does not have a chamber to provide pressure support to the excavation face. Excavated materials can be transported directly from the cutterhead.However, it can often to be combined with pressurised TBM but to operate without pressure (open mode).

TBM with Mechanical Face Support

Fl d d l d


Flood doors closed

Flood doors open

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Open Face




Shield TBM

Gripper TBM

Roadheader

Reaming Machine

Non-Shield TBM

Competent rock

Competent rock

Competent rock

Firm soil






Air Shield





Hybrid Shield



groundwater

Loose sandysoil


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When open face shield excavating groundwater-bearing soil, water penetration can be prevented by having the shield and a section of the tunnel protected by a lock system using compressed air.

The required pressure is monitored continuously and adjusted automatically where


necessary by a compressed air system consisting of two control circuits.

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Open Face




Shield TBM

Gripper TBM

Roadheader

Reaming Machine

Non-Shield TBM

Competent rock

Competent rock

Competent rock

Firm soil






Air Shield





Hybrid Shield



groundwater

Loose sandysoil


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The largest slurry shield φ15.43m (2006), used for Shanghai Changjiang Under River Tunnel Project.


Slurry / Hydro-ShieldTBM excavation face is supported by pressurizing bentonite in cutterhead chamber. Circulation of the fluid flushes out the muck. Pressure is maintained by controlling discharge rates.

1. Cutting wheel2. Air bubble3. Bentonite suspension4. Drive unit5. Stone crusher


5. Stone crusher6. Push cylinder7. Air lock8. Steer cylinder/ shield tail9. Segment erector10. Segment conveyor

MOVIE

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ADVANTAGES

Equal distribution of pressures against mixed-face conditions.Good performance in sands and gravels.Gives better face stability

LIMITATIONS

Need of large separation plants for bentonite separation and treatment.Not suitable for clayey-silty grounds.



Gives better face stability (formation of mud-cake). Allows access to the face with compressed air.

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Open Face




Shield TBM

Gripper TBM

Roadheader

Reaming Machine

Non-Shield TBM

Competent rock

Competent rock

Competent rock

Firm soil






Air Shield





Hybrid Shield



groundwater

Loose sandysoil


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The largest EPB machine φ15.2 m (2006) for Madrid M-30 project.



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TBM excavation face is supported by pressurizing earth inside the cutterhead chamber. Earth pressure in the h b i l t d


chamber is regulated by the rate of earth discharge through the screw conveyer.

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Earth Pressure Balance ShieldFoams and chemical additives are used to conditioning soil for better control of pressure and muck discharge, in sandy


in sandy grounds.

MOVIE

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ADVANTAGES

Very well adapted for excavating silty and clayey grounds.No need of separation plant.The use of additives (foams)

LIMITATIONS

Irregular distribution of pressure against mixed face conditions.Problems when boulders are encountered: no possibility of



The use of additives (foams) enables EPB’s to be used with sandy-gravely soils.

fitting a rock crusher.Wearing of the screw can lead to bad pressure distribution.More difficult access to the face than for slurry shields (no mud-cake is formed).

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Selection of Shield Boring MachineBased on Soil Grain Size Distribution


EPBSlurry

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EPB

Selection of Shield Boring MachineIncrease of EPB Use in Gravelly Grounds


EPBSlurry

EPB used –Chengdu Metro

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Open Face




Shield TBM

Gripper TBM

Roadheader

Reaming Machine

Non-Shield TBM

Competent rock

Competent rock

Competent rock

Firm soil






Air Shield





Hybrid Shield



groundwater

Loose sandysoil


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Mix-Shield

The cutterhead has combined features for hard rock and soil excavation. It enables the shield TBM to excavate through both rocks and soils, and rock-soil mixed face. Mix-shield can be EPB or slurry based.


Mix-Shield Slurry Mix-Shield EPB

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ADVANTAGES

Flexible in excavation of rock, soil, and mixed ground.Face pressure features are maintained by either EPB or slurry.

LIMITATIONS

Maintaining face pressure may be difficult, particularly for EPB based machine.Cutter wear and damage is generally high.

Mix-Shield


Other advantages of EPB or slurry shields.

Muck discharge may be difficult due to mixing of rock and soil.Other limitations of EPB or slurry shields.

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Open Face




Shield TBM

Gripper TBM

Roadheader

Reaming Machine

Non-Shield TBM

Competent rock

Competent rock

Competent rock

Firm soil






Air Shield





Hybrid Shield



groundwater

Loose sandysoil


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Double Shield

It combines the features of gripper and shield in a TBM, and enables fast excavation even in varying rock formations.

Gripper


Double Shield

In poor ground condition, it works as a single shield machine. When in rocks, grippers are used for forward movement, so segment can be simultaneously installed while excavating.


MOVIE

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ADVANTAGES

Good flexibility for varying grounds.High advancement rates. The increase depends on operation.

LIMITATIONS

Maintenance problems of articulation between the shields.Long shield length: possible drawback for squeezing

Double Shield


Possibility to have different support measures, e.g., segmental lining, and bolts-SC.Possibility of ground treatment and/or probing through the gap between shields.

grounds.More expensive than conventional shields.

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Open Face




Shield TBM

Gripper TBM

Roadheader

Reaming Machine

Non-Shield TBM

Competent rock

Competent rock

Competent rock

Firm soil






Air Shield





Hybrid Shield



groundwater

Loose sandysoil


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EPB-Slurry Convertible Shield

It is a machine has both EPB and slurry system installed. It can convert between EPB mode and slurry mode, to cope with grounds suitable for both type of machines.


Slurry Mode EPB Mode

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EPB-Slurry Convertible Shield


OpenMode EPB Slurry EPB

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Open Face






Gripper TBM

Roadheader

Reaming Machine

Non-Shield TBM

Competent rock

Competent rock

Competent rock

Firm soil


Steel set, bolt, SC, CCBolt, SC

Bolt, SC

Bolt, SC

C segments

C segments

C segments



Air Shield



groundwater

Loose sandysoil





Hybrid Shield


C segments

C segments

C segments, bolt, SCC segments

C segments

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New TBM Technologies

Optimizing underground space



Optimizing advancement


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Optimizing machine with variable ground condition



Under Water Shield – TIMBY



Open Face Weak, soft rock Firm soil


Gripper TBM

Reaming Machine

Non-Shield TBMCompetent rock

Competent rock

Firm soil

Bolt, sprayed concrete, cast-in concrete, steel set

Machine Ground Condition Support

Roadheader Competent rock

Digger Impact breaker, ripper, pick, and bucket for weak rock and soilBoom Excavator

Steel set, bolt, sprayed concrete, cast-in concrete







Loose sandysoil

Shield TBM


Double Shield Varying from rock to soil


Varying soils from sands to clays

Hybrid Shield Mix-Shield Mixed ground of rock and soil

Concrete segmental lining

Segmental lining, bolt, sprayed concrete

Concrete segmental lining

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Documents

Professor Jian ZHAO EPFL ENAC LMR TOS Laboratoire de ... 2011...EPB and slurry machines Hybrid Shield ... provide pressure support to the excavation face. Excavated materials can be