Protect Tunneling:
A tunnel is an underground passageway, dug by way of the encompassing earth and enclosed aside 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 Challenge underneath 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 throughout the excavation works for the Tunnel building underneath Karnaphuli River is air-cushion slurry strain balanced protect machine, manufactured by Tianhe Mechanical Tools 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, section dealing with system and section feeder and piping plan for the primary physique. The total 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 throughout the design stage of the Challenge. The manufacturing stage was 120 days from the center of Could 2017 after the acquisition of plates for the primary physique. It took 100 days extra for the meeting, commissioning and manufacturing unit 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 Major 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
• Major Air flow System
• Auxiliary Air flow System
• Steering 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 properly.
The sequence of set up of Protect Machine are as follows.
1.To start with, the Decrease bracket of the metal sleeve is hoisted in place;
2.Entrance (F2) & Center Protect (B3) Decrease half is hoisted all the way down to the shaft;
3.Drive half is hoisted all the way down to the shaft and assembling;
4.Entrance Protect Left (F3) & Proper (F4) and Higher (F1) Block are hoisted all the way 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 Delicate Floor Protect Machine.
• Spoke Sort;
• Plate Sort;
The reducing wheel is provided with totally different sorts of Reducing Instruments:
• Scrapers/Major Cutter-282 ;
• Previous/ Major Cutter-159;
• Shell Cutter-25;
• Put on Detector-2;
• Double Edge Heavy Obligation Tearing Cutter-12
• Peripheral Safety Cutter-25;
• Fish Tail Cutter-1;
TBM Supporting Trolley Meeting Scheme:
After Protect assembling, the match trolley is assembled as a way 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 strengthened soil which might help earlier than the TBM launch. The working shaft finish is consolidated by way of Ø1200@800 triple-tube HP chemical churning piles. To be able 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 space 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 House between the Partition and the Cutter Head is known as “SLURRY CABIN”. The slurry made from water, clay and components is pressed into the Slurry Cabin by way of the Pipeline and the slurry fills all the Slurry Cabin with a sure strain to type a slurry strain chamber. When the Protect Machine advances, the earth and sand minimize by the cutters is combined by the stirring gadget to type high-density slurry which is distributed to the Slurry Remedy Plant on the bottom by way 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, contemporary Slurry ought 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 combined 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 can be pumped into the slurry circulating pool after 24h to be used. The multi lane Highway Tunnel underneath the River Karnaphuli primarily passes by way of the cohesive soil and sand layer interbedded from shallow to deep and the entire part, positive 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 take care of its stiffness. A strain steadiness is constructed upfront throughout the sleeve after which the TBM passes by way of the portal to complete launching. The Counterforce bracket supplies a counter-force for TBM throughout TBM launch. Sand is crammed within the sleeve to supply drive 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 Interior 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 essential Parameters ought to be monitoring throughout TBM Advancing and
mining. For example:
Face Stress;
Major Grout Injection;
Grease & Lubricant Injection;
Aside from that it ought to be additionally monitoring others parameters by way of Arigatawa View;
• Common Stroke(=Precise Stroke)=1760 mm;
• CHS: 0.99 rpm;
• Most Stroke(Out of 4 Values)=1800 mm;
• Advance Velocity(NPR)=26mm/min(Restrict 20~30);
• Rotation Course: Clockwise/Anti-clockwise;
• PEN=(NPR/CHS)=15.99 mm
• Power: 97131 KN
• Power: 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 strain is utilized, it will 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 might need been brought on by a mistaken calculation of goal Face Stress or extra possible an unforeseeable change in soil situations.
Major/Annular Grout Injection:
Face Stress not solely the think about settlement, want to contemplate loss at tail void. Synchronous grouting is a vital measure to stop 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 Building:
Grout Stress;
Grout Quantity;
Grout Quantity: The theoretical quantity of the development hole between the cutter head and the section 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%
Therefore,
Q=Vα
=13.55X1.1
=14.9 cum
Or,
If the Soil Stratum is Silt Tremendous Sand, the
Injection fee can be 130%
Therefore,
Q=Vα
=13.55X1.3
=17.6 cum
Protect Tunneling Building
Protect Tunneling Building divided into 4 levels. For Occasion
• Launching Stage (-7 ~ +3 Ring):
• Preliminary Driving Stage (+4 ~ +22 Ring)
• Preliminary Driving Stage (+23 ~ +80 Ring)
• Closing Driving Stage (After Unfavorable 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 throughout the sleeve and slurry strain institution within the slurry pond. Then TBM breaks the underground diaphragm wall and enters the consolidated soil shifting ahead in 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 can be double marshaled, the Y-Swap and double monitor can be put in within the connecting space between launching shaft and tunnel.
6.The momentary rings can be eliminated.
7.Grout can be transported by locomotive within the tunnel and at last saved within the Major Grout tank in TBM.
Malfunction of TBM
Tunnel Boring Machine (TBM) tunneling tasks are continuously hit with delays which might trigger antagonistic 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 could 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 as a result of Cutter Head Torque being lowered from 3500 KN.m to 5000 KN.m. The Diver eliminated and Changed of three Peripheral Scrapers on the correct facet of #1 Spoke, the left facet of three# spoke and the correct facet of #4 spoke. Consequently, the Thrust drive of the Protect Machine has step by step elevated from 6000T to 13000T.
To sum up, protect tunneling building will depend on groundwater situations, 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 refined methods 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 properly.