Comprehensive report on Tunneling @ Abu Hamour Project_Qatar

A COMPREHENSIVE REPORT ON TUNNELING AT ABU HAMOUR SURFACE & GROUND WATER PROJECT PHASE – 1. DOHA, QATAR

By,

Faraj M. Fawzi, S.R.E

Ravinder Singh Sason, R.E – Tunnel

Pallav Sharma, Tunnel Engineer

A COMPREHENSIVE REPORT ON TUNNELING AT ABU HAMOUR SURFACE & GROUND WATER

PROJECT PHASE – 1. DOHA,QATAR

This report comprises of the general description about the different components/ parts of an EPB TBM.

The functioning of an EPB TBM is described. The lowering and assembling sequence of TBM is explained.

The template of the commissioning reports, required prior to the initial drive, for the TBM and backup

equipment’s/ machines is also provided for ready reference.

The procedures described in this report are limited to AHSO project viz., the component description, the

lowering sequence, assembling procedure, initial drive etc. The procedures are different for different projects

depending upon the geological conditions, site conditions, and availability of the space for lowering, erection

and assembling of a TBM.

The special feature of Earth Pressure Balance TBM is that it uses the excavated soil directly as the support medium.

The cutterhead excavates the material from the face; this soil enters the excavation chamber, where it is mixed with the

additives / soil paste. Mixing arms on the cutterhead and bulkhead mix the soil so that it comes in a conveyable form.

The bulkhead transfers the pressure of the thrust cylinders onto the excavated soil/ soil paste in the excavation

chamber. When the pressure of the soil paste in the excavation chamber equals the pressure of the surrounding soil

and ground water, the necessary balance is achieved.

The screw conveyor transports the excavated material from the base of the excavation chamber onto the belt conveyor.

A balance has to be maintained between the TBM’s advance rate and the screwing out of the material.

The screwing out of the material must ensure that support pressure in the chamber is maintained. The earth pressure is

continuously monitored with the help of Earth pressure Sensors in the chamber and in the screw conveyor, by the TBM

Operator

Cutter head

Screw conveyor

Excavation chamber

Mixing arms

Bulkhead Thrust cylinders Manlock Tailskin Backfill grouting

Segment lining Segment erector

Above figure demonstrates the working of an EPB TBM.

As the cutterhead turns, it cuts the face, the buckets on the cutterhead guide the material into the excavation chamber.

Where it is mixed, mixing arms do the work, with additive viz., foam and water, to make a conveyable spoil. The spoil is

moved out of the chamber by the screw conveyor, which in turn drops the material over the belt conveyor. The belt

conveyor carries the spoil all the way long from top of the backup gantries to the load out point.

System/ component description: -

Cutter Head -

It has variety of tasks:

Holding the excavation tools

Crushing stones to a conveyable grain size

Transporting the excavated material to the excavation chamber

Ground conditioning by injecting additives

Mixing the slurry via the mixing arms mounted on the rear

It comprises of a steel body which is equipped with various cutting tools depending upon the design, it also

consists of sprinklers for additives viz., water & foam, wear detectors & over cutter.

In order to achieve a longer service life, the cutterhead body, screw conveyor and cutting tools have been

provided with special wear protection.

Using back loading systems to change the cutting tools allows for the safe tool changing from the rear of the

cutterhead.

Depending upon the geology, the cutterhead is designed as a standard, mixed or rock cutting head.

The cutterhead of the TBM at ASHO project, is designed for mixed geology.

The cutter head of the TBM at AHSO project comprises of the following cutting tools: -

Scrapers/ Slab cutters: -

Remove cohesive and non-cohesive material by scraping/ scratching.

Disc cutters: –

Are installed on the cutter head into disc housings. They are so arranged that they touch the entire tunnel face

in concentric profile when the cutter head rotates. The cutting profile spacing and the diameter of the disc

cutter are selected to match the geological conditions and the achievable cutting capability.

The disc cutters start to rotate due to the contact pressure on the rock and the rotation of the cutterhead. In

doing so they breakdown hard rock by local overstressing. Ideally, this causes longish, plate like rock pieces of

rock or chips to break off.

Buckets: –

These collect the excavated material and guide them into the excavation chamber.

Tunneling machine: -

It comprises of a cylindrical body which is divided into several segments. The tunneling machine mainly

comprises of:

Front shield/ Shield

Middle shield/ Thrust pipe

Tailskin

The diameters of the individual segments continually decrease from head to tail. The rotating cutter head

thus creates an overcut between the geology and the tunneling machine. This cavity/ annulus gives machine

sufficient clearance during tunneling.

The steel structure of TBM is designed for the specified earth, water, traffic loads and the operational loads

that occur.

Front Shield -

It forms the front part of the TBM. The bulkhead is located on the front side of the shield, the area between the

cutterhead and bulkhead is known as the excavation chamber. The bulkhead transfers the thrust force to the

geology in front of the cutterhead.

It consists of the following parts: -

Compressed air lock: –

It is a compressed air lock for locking staff in or out for maintenance and repair work on the cutterhead and the

TBM.

The air lock is equipped with bulkheads and integrated air lock doors.

The air lock mainly comprises of the pre-chamber, main chamber and working chamber.

Main drive: –

It is designed as an annulus drive with a free center. It mainly consists of the following components –

i) Sealing system –

The drive is sealed against the soiling and water penetration by a combination of seals. The sealing system is

designed as a lip seal system with a total loss lubrication system and is continuously supplied with grease by a

grease pump.

ii) Rotary coupling –

It supplies the operating fluid and additives to the systems in the cutterhead viz., sprinklers, over cutter, wear

detector.

iii) Main bearing –

It absorbs the axial and radial forces that occur during excavation.

iv) Motor and Gearbox –

Electrical motors (06 no) are used as drive motors. They generate the required torque to operate the

cutterhead.

v) Lubrication system –

The bearing and gearbox are part-filled with lub oil and are splash lubricated.

Middle Shield -

It forms the middle part of the machine. It consists of the following components: -

Thrust cylinder –

These are required to advance the machine. They push the machine forward, transferring force to the bulkhead

which in turn transfers the force to the geology in front of the cutterhead, thus building face pressure.

Foam generator –

Liquid surfactant is mixed with water prior to entry into the generator. After that air is mixed with the

surfactant to create foam.

Drilling equipment –

It is used for surveying the geology and ground conditioning actions.

When needed, the drilling equipment is installed on the erector. That way the holes can be drilled through 360o

via the drill ducts on the tunneling machine.

It mainly consists of the following components:

Probe drill rig

Travel unit

Drilling hammer

Drilling lock

Hydraulic power unit

Control unit

Segment erector –

It is used for segment erection. Its kinematics is especially designed for the prevailing conditions and support

precise handling of the segments.

It mainly comprises of:

Steering –

Hydraulic cylinders known as steering articulation cylinders connect Front Shied to the Middle Shield. The thrust

cylinders in turn are connected to the tail skin via tail skin articulation cylinders. This means that all the

components are free to move with respect to the other, thus allowing tunnel radii to be followed even in sharp

curves.

The tunneling machine is steered by a combination of the shield articulation cylinders and thrust cylinders,

where the thrust cylinders are actuated in groups by means of pressure control. Individual shield articulation

cylinders and thrust cylinders are equipped with stroke measurement system.

Shield articulation seal –

It is located on the front side of the middle shield; it seals the connection between the front shield and the

middle shield.

The seal is built up as follows:

Sealing profile can be retroactively tightened

Replaceable sealing profile

Flushing

Screw conveyor –

It is a conveying system based on the working principle of Archimedes screw and comprising a series of several

pipes in which auger runs.

When the auger rotates, the screw conveyor transports the excavated material from the excavation chamber to

the belt conveyor. The feed rate is defined by the rotational speed of the screw conveyor and the degree of

opening of the screw discharge gate.

To avoid friction and clogging of the screw conveyor, additives can be directly injected into the screw conveyor.

Crusher function -

When the screw conveyor is running, rocks are broken down between the wear pipe and the screw conveyor

until they reach the conveyable grain size that will fit through the screw conveyor.

Telescopic function-

The screw conveyor is retracted in case of extended interruptions to tunneling operations, or for maintenance

and repair work. For this, a telescopic pipe is built into the screw conveyor, it is used to completely pull the

screw conveyor out of the excavation chamber.

The remaining opening is sealed by the screw conveyor front closing gate.

Screw conveyor front closing gate -

It separates the screw conveyor from the excavation chamber. It comprises of two flaps which are horizontal

displaceable via hydraulic cylinders.

Tailskin -

It forms the rear part of the tunneling machine. After each advance stroke, the tunnel is extended by

adding a newly built segment ring in the Tailskin.

Tailskin articulation seal –

It is located on the front side of the Tailskin; it seals the connection between the middle shield and the Tailskin.

Tailskin seal –

It is located at the end of the Tailskin. It is built up as a circumferential wire brush seal with grease loss

lubrication. At our project, it has three layers of wire brush seal with two grease chambers.

During mining, tail skin grease is pressed through the wire brush seals into the grease chambers via pipes. This

provides a seal against water, soil and filler material ingress.

Description of Backup gantries: -

Gantry 1 consists of: -

Bridge

Segment feeder

Ventilation duct

Extendable platform

Foam pump

Hydraulic tank (750 L)

TBM Operator Cabin


Grout tank (3.8 m3)

Grout transfer pump (04 nos.)

Ventilation duct


Accelerator tank (1.1 m3)

Storage & pump for Tail skin grease

Storage & pump for Lubrication grease

Membrane pumps


VFD (variable frequency drives)


Electrical distribution panels


1300 KVA Dry type Transformer

Switch cabinet MV


Waste water tank (2.7 m3)

Toilet cabin


Air receiver tank (750 L)

Air compressor

Diesel generator set (44 KW)


Cooling circuit pump

Cable drum 15 V


Man rescue chamber (10 persons max.)


Man rescue chamber (10 persons max.)


Hose drums (03 nos.)


Ventilation cassette

Work bench

Process technology: -

Ground conditioning:

The use of foam as a conditioning material is particularly suited to extremely heterogeneous soil

conditions with a high level of consistency in earth-pressure balance tunneling operations.

A foam-conditioned soil must fulfill the following process-related requirements:

Transferring the face support pressure to the tunnel face

Adequate ductility

Low water permeability

Distinctive resilience properties

Reduced clogging on the tunnel boring machine

Reduction of wear

Reduction of driving power

The principle of foam generation for earth-pressure balance tunneling is based on eddying of air with

foamable surfactant. For this, surfactant and water are mixed in configurable doses to create a liquid.

Mechanical eddying of air and liquid in a foam generator then produces the actual foam. For this, both

components are dosed via flow controllers and fed to the foam generator.

The dose is modified to reflect the soil characteristics, tunneling speed and face support pressure.

Foam can be injected via ball valves at the following points -

Cutterhead face side

Stators on the shield

Screw conveyor

Compressed air control unit:-

General description -

The compressed air regulating system uses an air bubble control the face support pressure in the

excavation chamber. The air pocket is adjusted to configure positive pressure by the compressed air

regulating system and kept constant. This compensates for influences such as pressure loss at the tunnel face.

During normal mining, the compressed air regulating system is inactive. It is only activated during

maintenance work, when the excavation chamber is emptied by drawing the soil in the chamber.

For safety reasons, there are two such circuits. This means that switchover to the standby occurs immediately,

when one system fails.

The system mainly consists of the following components:

Pressure transducers

Control units

Supply air control valves

Excavated material conveyor: -

General description –

The excavated material conveying system consists of the following components:

Screw conveyor

Belt conveyor.

Screw conveyor -

When the auger rotates, the screw conveyor transports the excavated material from the excavation chamber to a

belt conveyor. The feed rate is defined by the rotational speed of the screw conveyor and the degree of opening of the

screw conveyor discharge gate.

To avoid excessive friction and improve the material flow, additives can be injected into the screw conveyor pipe via

the injection holes.

The earth pressure is measured by pressure transducers known as earth pressure sensors and displayed to the

TBM operator in the control cabin.

Belt conveyor -

The belt conveyor transports the excavated material from the screw conveyor transfer point/ discharge point to

the transfer point in the back-up area, which is known as the muck discharge.

Depending upon the design, the excavated material is then transported onward via a rail-mounted logistics system

or a tunnel belt conveyor system.

Ring building: -

In ASHO project, a ring is composed of 7 segments i.e., 6+1. The rings are erected as per the guidance of VMT system.

The rings can be erected as per the following details in to 19 key positions: -

For ring erection the following ring sequence matrix is referred:

Backfilling:-

General description –

Because the excavated diameter of the tunnel is greater than the external diameter of the built rings, a cavity known

as annular gap is created during tunneling. To prevent settlement at the surface and stabilize the tunnel, this annular

gap needs to be backfilled.

Backfilling material –

Two component grout system

A two component grout system is used a filler material in backfilling.

The two component grout system comprises the grout (component A) and the accelerator (component B).

Both components are fed to the injection points through separate pipes. The accelerator is added to the grout

at the injection points via a valve.

Injection points –

Tailskin

The backfilling material is injected through the pipes in sync with the TBM advance. The pipes are distributed along

the circumference of the Tailskin.

Technical Specifications: -

Tunneling Machine -

Bore diameter 4520 mm

Cutting edge diameter 4490 mm

Front Shield diameter 4460 mm

Nominal cutterhead torque 2167 kNm

Intermittent cutterhead torque 2817 kNm

Continuously variable cutterhead rotational speed 0 - 4.5 min-1

Shield articulation cylinder -

Total cylinders 8 units

Number of cylinders with stroke 4 units

Measurement system

Number of cylinders without stroke 4 units

Measurement system

Maximum push force 14475 kN @ 400 bar

Maximum stroke length 300 mm

Main thrust cylinders -



Measurement system


Measurement system

Maximum push force 20891 kN @ 350 bar


Maximum extension rate 100 mm/min

Tailskin articulation cylinder -



Measurement system


Measurement system

Maximum push force


Erector -

Rotational speed 0-2 min-1

Nominal torque 160 kNm

Intermittent torque 175 kNm

Rotary angle + / - 200 degrees

Maximum permissible segment weight 1600 kg

Axial stroke 1050 mm

Radial stroke 664 mm

Screw conveyor -

Nominal diameter 600 mm

Installed power 110 kW

Nominal torque 59 kNm

Intermittent torque 74 kNm

Continuously variable rotational speed 0-46 min-1

Belt conveyor -


Continuously variable rotational speed 0-2.5 m/s

Belt width 650 mm

Theoretical capacity 450 m3/ h

Segment feeder -

Capacity 1 Ring (6+1)

Process technology: -

Hydraulics –

Power pack


Rotational speed 1500 min-1

Hydraulic tank capacity 750 L

Industrial water connection/ cooling circuit: -

Flow 40 m3/ h

Temperature 21 0C (max)

Pressure 10 bar (min)

16 bar (max)

Waste water pump –

Pump capacity 10 m3/ h

Waste water tank –

Capacity 2.7 m3

Backfilling: -

Number of injection lines 4+4 units

Number of pumps 4 units

Grout injection pumps –

Pump capacity 115 l/min

Grout tank –

Tank capacity 3.8 m3

Injection pump accelerator –

Pump capacity 10 l/min (max.)

Accelerator container -

Tank capacity 1.1 m3

Foam: -

Number of foam generators 4 units

Number of pumps 1 unit

Pump –

Pump capacity 1.4 m3/ h (max)

Installed power 1.1 kW

Surfactant tank –

Capacity 1100 L (max)

Polymer container –

Capacity 500 L (max)

Compressed air: -

Compressor –

Number 1 unit

Flow rate 5.78 m3/ min

Pressure max. 8 bar


Compressor air tank –

Number 1 unit

Capacity 750 L

Pressure max. 11 bar

Transport data: -

Cutterhead –

Length 1217 mm

Width 4396 mm

Height 4396 mm

Front shield –

Length 3910 mm

Width 4490 mm

Height 4490 mm

Middle shield –

Length 6853 mm

Width 4455 mm

Height 4455 mm

Tailskin –

Length 3798.6 mm

Width 4707.7 mm

Height 4707.7 mm

Screw conveyor

Length 13312 mm

Width 1186 mm

Height 1540 mm

Back-up area: -

Segment feeder –

Length 13826 mm

Width 2804.4 mm

Height 707.7 mm

Gantry 1 –

Length 16571.5 mm

Width 3365.5 mm

Height 3506 mm

Gantry 2 –

Length 7725 mm

Width 3131 mm

Height 3101 mm

Gantry 3 –

Length 7950 mm

Width 3105 mm

Height 3109 mm

Gantry 4 –

Length 7950 mm

Width 2945 mm

Height 3110 mm

Gantry 5 –

Length 7950 mm

Width 2945 mm

Height 3110 mm

Gantry 6 –

Length 6950 mm

Width 3239 mm

Height 3031 mm

Gantry 7 –

Length 7200 mm

Width 3255 mm

Height 2741 mm

Gantry 8 –

Length 6950 mm

Width 3190 mm

Height 2897 mm

Gantry 9 –

Length 8567 mm

Width 3180 mm

Height 3014 mm

Gantry 10 –

Length 8510 mm

Width 3255 mm

Height 2797 mm

Gantry 11 –

Length 8510 mm

Width 3255 mm

Height 2797 mm

Gantry 12 –

Length 7950 mm

Width 3238 mm

Height 2991 mm

Gantry 13 –

Length 9882 mm

Width 3148 mm

Height 3129 mm

Segment crane –

Length 24760 mm

Width 1165 mm

Height 1105 mm

Bridge –

Length 9969 mm

Width 2208.5 mm

Height 1104 mm

Lowering & Assembling of TBM:-

Different components of TBM are lowered using Cranes, of different lifting capacities, into the shaft

bottom.

Two types of cranes used are: -

500 MT variable boom length hydraulic crane; Make: - Liebherr

50 MT Gantry Crane; Make: - Demag

Heavy parts of TBM viz., Front Shield, Middle Shield and Cutter Head were lowered using 500 MT hydraulic

crane. Rest of the parts /components were lowered using 50 MT Gantry Crane.

The weight of different parts of TBM: -

Cutter Head - 28.0 T

Front Shield - 74.0 T

Middle Shield - 75.0 T

Tail Skin - 18.0 T

Gantry 1 Bridge - 5.0 T

Gantry 1 Platform - 15.0 T

Erector Head - 4.0 T

Gantry 2 - 11.5 T

Gantry 3 - 8.5 T

Gantry 4 - 9.0 T

Gantry 5 - 8.5 T

Gantry 6 - 10.0 T

Gantry 7 - 6.8 T

Gantry 8 - 8.8 T

Gantry 9 - 8.5 T

Gantry 10 - 8.7 T

Gantry 11 - 8.0 T

Gantry 12 - 9.3 T

Gantry 13 - 6.4 T

Selection of crane: -

A crane is selected based on the following calculations –

Weight of component/ part to be lifted, x

Weight of the lifting accessories viz., D-shackles, wire rope slings, lifting beam etc., y

Total weight to be lifted, z = x + y

The distance of point of lowering from the point of lifting is calculated, load chart of the crane is

referred for this calculation. Then the lifting capacity of the crane, the boom length required & the safe

working radius is found out from the load chart.

The max. Weight, z to be lifted should never be more than 85% of the lifting capacity of the crane at

that particular radius & boom length.

The crane fulfilling the above criteria is selected.

Lowering sequence: -

Lowering of Cutter head, Front shield and Middle shield shall be lowered by 500 MT Hydraulic crane. The tail

skin, Erector head, Screw conveyor, backup gantries and other components, parts & materials will be lowered

by 50 Mt Gantry crane.

All backup gantries are shifted to the place of lifting using a 70 MT mobile Hydraulic crane and trailer.

Front shield was lowered using 500 MT hydraulic crane. It was rested at the shaft bottom on the Skid

beam. It was then centered to the Tunnel alignment using Spirit Level, Measuring Tape and Steel Scale

(1 m).

It was followed by lowering of Middle Shield. It was rested at the shaft bottom on the Skid beam. It was

then centered to the Tunnel alignment using Spirit Level, Measuring Tape and Steel Scale (1 m).

Shield articulation seal was filled with grease.

O-rings were put in place in Front shield (Bull Gear) and the mating parts were thoroughly greased, to

minimize friction.

Then Cutter head was lowered and was assembled to the Front Shield.

Lowering of the erector head and assembling with Middle shield.

It was followed by lowering and assembling / fitting of Screw conveyor into the shields.

Then the bridge was fitted / assembled into the Middle Shield.

It was followed by assembling of tail skin with the Middle shield. Articulation seal was filled with grease.

The location of all the TBM components to be lowered is marked by he surveyor.

Lowering of Front Shield

Centering of shield:

Lowering of Middle Shield:

Preparation of Front shield for Cutterhead installation:

Lowering of Cutterhead:

Assembling of Cutterhead with shield:

Cutterhead assembled with front shield & middle shield connected:

Segment erector assembled with middle shield:

Lowering of Screw conveyor:

Lowering of Tailskin:

Assembling of front shield and middle shield:

Assembling of screw conveyor, Tailskin and gantry 1 bridge:

a

Assembling of Tailskin, middle shield and front shield:

The assembled machine is now pushed forward towards the concrete saddle, using the following procedure: -

Three thrust cylinders (invert) and two D-type segments along with the fastening / tying arrangements, thrust

arc, thrust beam, and an external power pack were used. The two D-type segments are so placed that the

shorter side of the segments touch each other. One side of the one D-type segment is in contact with the three

thrust cylinders, and the other side is in contact with the one side of the second D-type segment. The thrust ring

is installed on the outer side of the second D-type segment. The thrust arc in turn is in contact with the two

Thrust beam one on each side. The Thrust beam is mounted on skid beam with nuts & bolts. As the machine is

pushed forward using the combination, the position of Thrust beam is changed after every push of 1600-1800

mm. (see photos). This process is continued till enough space for lowering of Backup gantry -1 is available. The

thrust cylinders used for pushing the machine forward are operated by external hydraulic power pack.

The rail track for backup gantries is setup / installed.

Backup gantry -1 is lowered and connected to the shield and Gantry -1 Bridge.

The shield pushing continues in the same fashion, and special steel supports for the backup gantries are

lowered.

The pushing continues in the same fashion, till enough space for lowering of Backup gantry -2 is

available.

Backup gantry-2 is lowered and pushed towards opposite side Non-TBM tunnel till enough space is

available for the lowering of Bridge.

The Bridge is lowered and is connected to Gantry-1 and Gantry-2.

Same procedure as mentioned in 2) and 3) is followed for all backup gantries i.e., gantry -3 to gantry -

13.

While pushing the machine forwards, lowering and installation of single rail track for rolling stock is

carried out in parallel. The complete train is parked in the opposite Non-TBM tunnel.

As soon as the TBM reaches the launching area / Initial drive position inside the Non-TBM tunnel, the

erection of thrust frame is done.

Backup gantries -1 to 7 are used for initial drive up to ring # 57. Till that ring backup gantries 8 – 13,

which are lowered in parallel, are parked in the opposite tunnel.

After ring # 57, all backup gantries are connected to the machine and the TBM in all sense is completely

assembled, starting from cutter head to backup gantry-13.

After assembly of the TBM and backup gantries, conveyor belt is installed on the frame.

Machine pushing setup:

D - TYPE SEGMENT

THRUST BEAM THRUST ARC SKID BEAM

THRUST CYLINDERS

TYING ARRANGEMENT VIZ., WEB BELT, RACHET

LEVER HOIST,D-SHACKLE ETC.

Hydraulic power pack used:

Initial drive of TBM: -

After the TBM machine part assembled till backup gantry-7 is pushed at the launching frame. The following

procedure for the Initial drive will be followed: -

Excavation for Rings 3 to 10.

Excavation of Rings 11 to 57.

Excavation of Rings 58 to 115.

Prior to the excavation for ring no 3, following activities to be executed: -

Erection of ring 1 & 2. The key selection for them is done based on the Tail Skin clearance, considering the Ring

Rose & Ring Matrix. A Thrust ring is installed in the open periphery of ring 1 i.e., Non-TBM tunnel face.

Ring 1 & 2 are pushed towards the thrust frame, by the thrust cylinders. The thrust ring installed is rested

against the thrust frame, which provides the necessary reaction force required pushing the TBM forward, as the

mining for ring 3 progresses and thrust cylinders are pushed against ring 2.

During the first stage of mining the TBM will break through the steel fibers reinforced shotcrete wall. The

TBM shall be started in “Open Mode” with the advance rate less than 20 mm/min. Low advance rate is

recommended to

Limit the TBM roll due to absence of limited friction between the concrete saddle & shields.

Limit the thrust force to max. of 25 % of maximum thrust force capacity of 20500 KN.

Limit displacements and cracking / damage of ring 1 to 9.

During the TBM initial drive the last 13m section of the rails in the Non-TBM tunnel will be raised using temporary

steel supports to reach the invert level of the segmental lining. This raised rail track is used to travel a special trolley

and transporting initial segments inside tail skin to feed the segment erector. For Ring 1, it is preferable to select

a combination in which segment D is installed first, in invert level to ease the installation. Ring combination “U

18” shall be followed.

This procedure is adopted for transportation and handling of ring 3 to 9, until there is enough space to erect segment

feeder in the Tail skin.

The first 9 rings will be installed in the concrete saddle and will not be grouted. To limit their displacement during the

initial drive, they shall be wrapped using steel cables which shall be secured to the anchor plates embedded into stage

III of concrete saddle. Steel plates and brackets shall be installed in some of the rings across radial and circumferential

joints, to secure the blind/ false rings. Hydraulic pulling cylinders are used to pull and tension the steel cables, to apply

uniform hoop force along the ring extrados. This will prevent he birdsmouth opening and cracks in the false rings.

The ropes are tensioned to a max of 150 KN. In addition, props are used to hold the false rings from both sides. The

props are held against the ring extrados and the Non-TBM tunnel wall inner face. Pea gravel (size 3-5 mm) is injected

from both sides to fill the gap between the concrete saddle and the ring extrados. A temporary stop-end is used in

order to seal the gap between first ring and the concrete saddle preventing pea gravel flowing out in the Non-TBM

tunnel.

Ring 10, will be first ring erected entirely inside the mined tunnel. The gap between the ring extrados and the mined

tunnel shall be filled completely with dry shotcrete, preventing the flow of grout in the Non-TBM tunnel.

Upon completion of ring 10, once the segment feeder is completely installed, the horizontal track installed shall be

removed and joined with 1.5 % ramp joining the rail level in the TBM tunnel to the rail level in the AS 11, bottom.

This configuration will remain unchanged till the completion of ring 115. The rail track extension for the rolling stock

and the backup gantries shall be continuously extended according to the advance of the TBM. The ramp will enable the

train to reach the segment feeder where the segments will be lowered. The feeder shall deliver the segments to the tail

skin area providing feed to the segment erector for its erection.

Rings shall be installed according to the combination provided by the VMT system. The key position provided by the

VMT system, shall be cross checked with Ring Rose and sequence shall be checked using Ring matrix.

During this stage backup gantry 8-13 are parked in the opposite side Non-TBM tunnel. All hydraulic and electrical

connections between gantry 7 and shaft for the operation of TBM shall consist of flexible hoses laid along the tunnel

and continuously extended as the TBM advances.

Upon completion of first 57 rings (i.e., 74 m) gantry 8 to 13 shall be shifted from the Non-TBM tunnel to the launching

Non-TBM tunnel and connected to gantry 7. The 74 m of excavation will ensure that gantries 1-7 are completely

inside mined Tunnel. At this stage the TBM is in complete configuration and excavation/ mining shall continue in the

same manner till the completion of ring 115.

Mucking Out: -

During mining the face is excavated by the cutter head, the excavated material is pushed inside the excavation chamber

by the buckets installed on the cutter head. Additives viz., foam and water are added during excavation and in the

excavation chamber to condition the excavated muck and make a transportable spoil. The spoil from the excavation

chamber is screwed out by the screw conveyor and the feed is provided to the belt conveyor, which in turn carries the

excavated muck / spoil to the muck out point at gantry 7. The spoil is offloaded into muck skips (cap. 8 m3) which is

mounted on flat cars and driven by Diesel Locomotives. The Loco will travel to the bottom of AS 11 carrying the loaded

muck skips. The muck skips are lifted to the shaft surface by 50 T gantry crane and are offloaded at the designated area.

A tilting frame is used to tilt the skip for offloading. The empty muck skips re lowered back to the flat car the bottom of

AS 11.

The muck/ spoil collected on the surface is loaded by a wheel loader on to dumpers, which is then carried out and

dumped at the designated area.

Backfill Grout Injection: -

Starting from ring 10, backfill/ primary grout shall be injected from the tail skin , to fill the annulus between

the ring extrados and the excavated tunnel.

The backfill grout shall consist of the following components: -

Component A – mix of cement, bentonite, water and retarder.

Component B – sodium silicate – accelerator.

Component A shall be mixed and batched at surface using the grout plant installed at AS 11 and shall be

transferred to the TBM grout tank through the 2.5” line installed all along the tunnel. Component B shall be

stored in silos at surface and shall be transferred to the TBM in 1 m3 IBC’s (Intermediate Bulk Container).

Component A and Component B shall be transferred separately from the surface to TBM and will only be

mixed only at the time of injection, in the rear end of the tail skin.

Injection of grout is carried out simultaneously as the mining advances. The injection ports are equally

distributed along the tail skin in order to allow for the uniform distribution of grout and complete filling of

the annulus.

Supply of Construction Materials: -

The foam agent is separately supplied in liquid form in IBC’s (Intermediate Bulk Container). These are lowered

on flat car and are carried into the TBM by the Loco and pumped into the foam tank at gantry 1.

The tail skin grease (TSG) shall be supplied in 250 kgs, and are transported into TBM on flat car. They are

unloaded at gantry 3 and it is connected to the grease pump for its intended use.

The TBM lubricant grease is transported as in 2) and is connected to the grease pump at gantry 3.

All other materials viz., rails, sleepers etc., are transported into TBM using flat car.

Commissioning of TBM

TBM as a whole, its different components and the supporting equipment’s/ machines viz., grout plant, rolling stock

(diesel locomotive, flat car, segment car, passenger car & muck car), diesel generators, chiller, 50 T gantry crane are

commissioned based on the parameters & guide lines laid down by the OEM.

TBM: -

Workshop acceptance report –

Grout plant: -

Commissioning check list

Rolling stock: -


Chiller: -


50 T Gantry crane: -


1250 KVA diesel generator: -


Documents

Comprehensive report on Tunneling @ Abu Hamour Project_Qatar