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Pipe Jacking Design and Best Installation PracticePrepared by the
Pipe Jacking Association
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Key Considerations
Pipe Jacking is an integrated system linking:
soils
jacking shafts
pipes
shields
jacking loads
engineering
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Soils Investigation
Soils investigation is key:
This influences
excavation method
temporary works
length
pipes
ground stabilisation
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Differing ground needs to be assesed as appropriate:
Non-cohesive soils
Cohesive soils
Mixed soils
Fill
Rock
Water presence is a key factor
Soils Data Requirements
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Unstable Ground Conditions
Tunnelling methods depend on
the stability of the ground
Solutions to instability are
either geotechnical processesor physical constraint
Geotechnical options are extensive
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Excavation: Open Face
Hand shields
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Excavation: Open Face
Hand shields
Backacter
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Excavation: Open Face
Hand shields
Backacter
Cutter boom
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Excavation: Closed Face
Pressurised slurry
Compressed air
Earth pressure balance
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Temporary Works: Shafts and Shield Entry
Segmental
Precast or insitu
Piled
Sheeted or timbered
Battered
Anchorages
Shield entry and exit
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Temporary Works: Thrust Walls
The thrust wall takes the full jacking load
Spreaders distribute the load
Thrust wall failure key risk
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Temporary Works: Manholes
Manhole requirements vary
Shafts bases can be enlarged
Caissons can fulfil mutiple roles
Manhole utilisation impacts on
project costs
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Jacking Lengths and Friction Loads
Design variables include:
thrust walls
pipe design
interjacks
friction lubricants
spoil removal
engineering
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Jacking Loads
Jacking loads comprise:
face loads
pipe string weight
friction
misalignment
time delays
Frictional forces 0.5 to 2.5 tonnes per square metre
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Lubrication
Bentonite
Soil type dependent
Foams
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Pipe Jacking Pipes
Concrete jacking pipes: EN 14457
Installation forces are key
Follow manufacturers recommendations
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Best Installation Practice: Loading
Thrust load and anchorage
Load transfer
Control/failsafe
Interjacks
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Best Installation Practice: Steering
Tolerances: 75mm for line, 50mm for level
Setup and shield entry
Regular checks
Cautious realingment
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Best Installation Practice: Records
Monitoring
Main survey checks
Line and level
Shield position
Pipe rolling Main jacking load
Interjack load
Shield load
Total load
Surface checks
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Summary
Design: Ground
Excavation method
Temporary works
Jacking loads
Lubricants
Pipes and joints
Installation: Steering
Loading Records
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Pipe Jacking Association10 Greycoat Place, London SW1P 1SB
Tel: 0845 070 5201 Fax: 0845 070 5202
Email: [email protected]
Website: www.pipejacking.org
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