In This Article We Covers Needle Beam Method Of Tunneling In Soft Ground.
FACTOR AFFECTING THE CHOICE OF A METHOD
- SIZE OF TUNNEL
- TYPE OF GROUND
- AVAILABLE EQUIPMENT
- METHOD OF SEQUENCE OF EXCAVATION
NEEDLE BEAM METHOD
Needle Beam Method Suitable For Firm Ground And Brick Lining.
It Consist Of A Stout Timber Beam From Main Temporary Support.
Needle Beam Method Used When The Soil Roof Can Stand For A Few Minutes.
Length Of Needle Beam 5 m To 6 m.
SEQUENCE OF OPERATION Of NEEDLE BEAM METHOD OF TUNNELING
A Money Drift For Short Distance Of 900 mm Driven Beyond Day’s Work, On The Working Face.
The Roof Of Drift Supported By Lagging Carried On Wooden Segments, Which In Turn Supported By Two Trench Jacks In Front And 2 In Rare.
After This Drift Is Completed Needle Beam Is Slowly Skidded Forward Into Monkey Drift.
Front End Of Beam Rests On Plank While The Rare End Supported By Stout Post Resting On The Lining Of The Tunnel Floor.
A Trench Jack Is Now Placed On The Center-Line Of The Needle Beam To Support The Segment, Thus Transferring Roof Load To Needle Beam.
The Other Trench Jacks Removed And Widened Sideway (Drift) And Supported As Before Arrangement.
Segments At Crown As Well As Sides When Reach Up to Invert Level, They Complete Ring Of Segment To Get Arch Action Adjacent Segments Are Connected By Timber Wedges.
Now All Jacks Released As The Earth Load Transferred To The Arch Segments, Needle Beam Further Pushed And Complete Procedure Repeated.
*Large Number Of Jacks Required.
Advantages Of Needle Beam Method
Needle Beam Method Is Economical.
Works All Right On Brick Lining.
Disadvantages Of Needle Beam Method
Heavy Beam Pushed Forward By Hand.
Number Of Trench Jacks Required.
Needle Beam Method Difficulties In Concrete Lining With Machine.
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Founder Of “KPSTRUCTURES”