Shield Tunneling: Air-Cushioned Slurry Balanced Shield Machine

Protect Tunneling:

A tunnel is an underground passageway, dug by means of the encompassing earth and enclosed apart from entrance and exit. The primary tunneling protect was developed by Marc Isambard Brunel in January 1818 beneath the Thames River in London. The Bangabandhu Tunnel Mission below the Karnaphuli river is designed as a single layer 4-lane dual-carriageway with two protect tunnels.

Tunnel Boring Machine(TBM):

The Tunnel Boring Machine (TB) used in the course of the excavation works for the Tunnel building below Karnaphuli River is air-cushion slurry stress balanced protect machine, manufactured by Tianhe

Mechanical Gear Manufacturing Firm Restricted (CCCCTH). The diameter of the Cutterhead was 12.12m with a 13.6m lengthy protect part.

The manufacturing of the TBM used for the tunnel was initiated in March 2017 by preparation of drawing of cutterhead, protect skins, erector, trolly construction, phase dealing with system and phase feeder and piping plan for the principle physique. The complete design was finalized on the finish of July 2017. The order for the manufacturing of this slurry protect TBM was positioned in April 2017 by CCCC in the course of the design stage of the Mission. The manufacturing stage was 120 days from the center of Could 2017 after the acquisition of plates for the principle physique. It took 100 days extra for the meeting, commissioning and manufacturing facility acceptance check as much as finish of December 2017

The principle parts of the TBM are the followings:

• Protect Physique (entrance, center and tail protect)
• Cutters & Copy cutter
• Drive System
• Grease & Lubrication System of Important Bearing
• Agitator
• Air Stress Management System of Air Chamber
• Propulsion System
• Section Erector
• Cooling Water System
• Waste Water Discharge System
• Slurry Transportation System
• Man-lock
• Pipeline extension System
• Synchronous Grouting System
• Section Storage & Transportation
• Secondary Grouting System
• Air Compressing System
• Industrial-Managed Compressor System
• Emergency Producing Set
• Important Air flow System
• Auxiliary Air flow System
• Steerage System

Protect Machine Meeting Scheme:

Every protect is split with 4 parts-Higher Block, Left and Proper Block and Decrease Block. For Protect Machine Lifting, 500t Tremendous Crawler Crane are used for Hoisting and assembling within the working effectively.

The sequence of set up of Protect Machine are as follows.

1.To begin with, the Decrease bracket of the metal sleeve is hoisted in place;
2.Entrance (F2) & Center Protect (B3) Decrease half is hoisted right down to the shaft;
3.Drive half is hoisted right down to the shaft and assembling;
4.Entrance Protect Left (F3) & Proper (F4) and Higher (F1) Block are hoisted right down to the shaft;

Cutter Head:

The Cutter head is assembled on the Floor. Two Crawler cranes are used to show over the cutterhead and decrease into the working shaft. The general lifting weight of the cutterhead is 220T.

There are two sorts of Cutter Head for Mushy Floor Protect Machine.

• Spoke Sort;
• Plate Sort;

The reducing wheel is supplied with totally different sorts of Slicing Instruments:

• Scrapers/Important Cutter-282 ;
• Previous/ Major Cutter-159;
• Shell Cutter-25;
• Put on Detector-2;
• Double Edge Heavy Responsibility Tearing Cutter-12
• Peripheral Safety Cutter-25;
• Fish Tail Cutter-1;

TBM Supporting Trolley Meeting Scheme:

After Protect assembling, the match trolley is assembled so as to the on-site meeting of 1# , 2#, 3# and 4# in response to the reserved lifting gap (Size 20mXWidth 7.5m) at C&C part.

Cutter Head:700mm

Trolley-1: 14.35m

Trolley-2: 17.65m

Trolley-3: 14.50m

Trolley-4: 16.80m

Previous Works of TBM Launch: Vertical Freezing Reinforcement:

Vertical Freezing Reinforcement is a option to bolstered soil which may help earlier than the TBM launch. The working shaft finish is consolidated by the use of Ø1200@800 triple-tube HP chemical churning piles. So as to keep away from cutter disc put on when the protect begins, vertical Freezing Reinforcement is used.The thickness of the freezing wall is 1.5 m, the width is 16.0 m, and the freezing depth is 25 m. The primary row of holes is 400 mm from the facet line of the concrete groove wall, the gap between the holes is 800 mm, together with 21 ones. The second row is 800 mm aside from the primary row, staggered with the primary row in plum blossom form in 20 holes.

On the again facet of the Cutter Head of this Protect Machine, a Protect Partition is put in. The Area between the Partition and the Cutter Head is called “SLURRY CABIN”. The slurry made from water, clay and components is pressed into the Slurry Cabin by means of the Pipeline and the slurry fills the complete Slurry Cabin with a sure stress to type a slurry stress chamber. When the Protect Machine advances, the earth and sand reduce by the cutters is blended by the stirring system to type high-density slurry which is distributed to the Slurry Therapy Plant on the bottom by the use of fluid transportation and the soil and water are separated after which again to the Slurry Cabin.

Previous Works of TBM Launch: Set up & Debugging of Slurry Station:

Earlier than Protect Tunneling begins, recent Slurry needs to be ready and saved within the slurry tank. Uncooked supplies of slurry are bentonite and water, and the proportion of bentonite and water (combine ratio) is 1/0.135.The uncooked supplies are blended with high-speed rotary mixer after being put into the preparation barrel. After mixing, the slurry is saved in a slurry storage pool for standby and shall be pumped into the slurry circulating pool after 24h to be used. The multi lane Highway Tunnel below the River Karnaphuli primarily passes by means of the cohesive soil and sand layer interbedded from shallow to deep and the entire part, advantageous sand layer is excavated. Add 45t Bentonite to every of the ten rings after tunneling. When mixing, add the clay slurry which is saved within the earlier interval to cut back the quantity of bentonite.

Previous Works TBM launch: Set up of Metal Sleeve:

Earlier than TBM Launch, the Protect Machine is sealed with the Metal sleeve. The Metal Sleeve is a 20mm thick Metal Plate on which is supplied with a rib plate to keep up its stiffness. A stress steadiness is constructed upfront inside the sleeve after which the TBM passes by means of the portal to complete launching. The Counterforce bracket supplies a counter-force for TBM throughout TBM launch. Sand is stuffed within the sleeve to offer pressure of friction and resist towards twisting. An Anti-torque Rib is welded on the TBM to withstand towards torque.

• The Outer Diameter of the Metal Sleeve=12924mm
• The Inside Diameter of the Metal Sleeve=12484mm
• The Clearance between the Metal Sleeve & the TBM physique =182mm

Tunneling Parameter Management Throughout TBM Advancing:

There are three vital Parameters needs to be monitoring throughout TBM Advancing and
mining. As an example:

Face Stress;

Major Grout Injection;

Grease & Lubricant Injection;

Other than that it needs to be additionally monitoring others parameters by means of Arigatawa View;

• Common Stroke(=Precise Stroke)=1760 mm;
• CHS: 0.99 rpm;
• Most Stroke(Out of 4 Values)=1800 mm;
• Advance Pace(NPR)=26mm/min(Restrict 20~30);
• Rotation Path: Clockwise/Anti-clockwise;
• PEN=(NPR/CHS)=15.99 mm
• Drive: 97131 KN
• Drive: 97131 KN
• Density Inlet D2 & Outlet D1
• Flowmeter F1 & F2

Face Stress:

Formation Stress on the Protect Machine together with Earth Stress and Water Stress is named Face Stress. Establishing and Sustaining Right Face Stress for the Floor and Groundwater Situations is essential to the protected operation of TBM. If insufficient face stress is utilized, this may result in extreme Floor Settlement and will end in collapse of the tunnel face.Over 100 incidents in final 10 years over EPB and Slurry Protect Drives. The cave-in may need been brought on by a mistaken calculation of goal Face Stress or extra seemingly an unforeseeable change in soil circumstances.

Major/Annular Grout Injection:

Face Stress not solely the consider settlement, want to think about loss at tail void. Synchronous grouting is a crucial measure to forestall stratum settlement. There are six Grout Injection Factors on the Protect Tail.

Two parameters are management to make sure the backfilling high quality of grout throughout Development:

Grout Stress;

Grout Quantity;

Grout Quantity: The theoretical quantity of the development hole between the cutter head and the phase is:

V = π/4 x (12.16²-11.80²) x2 m³/ring

The Injection Quantity Q of the Backfilling Grout can often be estimated by the next System:,

Q=Vα, the place, V= Theoretical Quantity
α= For Instance,

If the Soil is Mucky Silty Clay, the injection fee ought to be110%


=14.9 cum

If the Soil Stratum is Silt Nice Sand, the
Injection fee shall be 130%
=17.6 cum

Protect Tunneling Development

Protect Tunneling Development divided into 4 levels. For Occasion

• Launching Stage (-7 ~ +3 Ring):
• Preliminary Driving Stage (+4 ~ +22 Ring)
• Preliminary Driving Stage (+23 ~ +80 Ring)
• Ultimate Driving Stage (After Unfavourable Rings Eliminated)

After the completion of TBM and metal sleeve set up -7 and -6 have been assembled and related and pushed to the round ring on the metal sleeve finish.

2.Then dense sand filling inside the sleeve and slurry stress institution within the slurry pond. Then TBM breaks the underground diaphragm wall and enters the consolidated soil transferring ahead in the direction of the portal.
3.Begin Synchronous Grouting and Tail grease system.
4.After TBM development 2.0, Assembling -5 ring and set up of 1st Group of Splayed wheel by 1#lorry
5.After the 80 rings of tunneling have been completed, the locomotive shall be double marshaled, the Y-Swap and double monitor shall be put in within the connecting space between launching shaft and tunnel.
6.The momentary rings shall be eliminated.
7.Grout shall be transported by locomotive within the tunnel and eventually saved within the Major Grout tank in TBM.
Malfunction of TBM
Tunnel Boring Machine (TBM) tunneling initiatives are often hit with delays which may trigger opposed results, extending schedules and incurring extra prices.There are 4 causes that play instrumental behind the Malfunction of TBM Advancing.
• Hydraulic Malfunction
• Hydraulic Malfunction
• Electrical Malfunction.
• Others Malfunction.

Tunnel Lining:

There are 23 Factors in Complete and eight positions may be chosen for the important thing place of the following ring:
Hyperbaric Intervention of Cutter Head Substitute
Throughout Protect Tunneling, a CHI has been carried out attributable to Cutter Head Torque being lowered from 3500 KN.m to 5000 KN.m. The Diver museumbola eliminated and Changed of three Peripheral Scrapers on the proper facet of #1 Spoke, the left facet of three# spoke and the proper facet of #4 spoke. In consequence, the Thrust pressure of the Protect Machine has steadily elevated from 6000T to 13000T.
To sum up, protect tunneling building relies on groundwater circumstances, the size and diameter of the tunnel drive, depth of the tunnel and applicable danger administration. I do imagine that we ought to stay in contact with subtle strategies to construct a tunnel by air-cushioned slurry balanced Protect machine and it’ll foster and sturdy our life and usher in a brand new period of our regime as effectively.

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