TUNNEL CONSTRUCTION

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TUNNELCONSTRUCTION

• KYLE DENNY

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History

• Dates back for centuries
• Aztec, Inca, Babylonian,
• Egyptian, and Persian
• Wide Range of Applications
• Extremely Slow
• Incredible Advancement
• Length 33.5 miles Seikan Rail Tunnel
• Cross Section 1700 ft2 Uetliberg Tunnel
• Depth 787 feet Seikan Rail Tunnel

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Function of Tunnels

• Mining
• Utilities
• Water Supply
• Sewage Transport
• Transportation
• Automobile
• Train

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Methods of Construction

• Cut and Cover
• Mountain Tunneling Method
• Boring
• Blasting

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New Urban Tunneling MethodBaikoh Tunnel
Excavation

• Introduction
• Site Conditions
• Design
• Construction
• Measurement Results
• Conclusions

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Introduction

• Mito City, Ibaraki Prefecture
• Highly Congested
• Located below NHR 349
• Three
• methods
• considered

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Tunnel Characteristics

• Total Length 607 m
• Large Cross Section 102 104 m2
• Shallow Overburden 6 11 m
• Close proximity to utilities and structures
• Unconsolidated ground
• High groundwater

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Site Conditions

• Geology
• Upper gravel layer (Dg1)
• Lower clay layer (Dc2)
• Lower gravel layer (Dg2)

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Upper Gravel Layer

• Dg1
• Lies along top heading
• Two types
• Gravel Stratum with clay
• Gravel Stratum
• Groundwater 2-4 m above bottom of layer

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Lower Clay Layer

• Dc2
• Main part of tunnel
• Overconsolidated soft clay
• Two problems
• Surface settlement
• Impervious

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Lower Gravel Layer

• Dg2
• Invert of Tunnel
• Dense Gravel
• Solid Foundation

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Surrounding Environment

• Busy Traffic Area
• Many Utilities
• Water
• Sewer
• Gas
• Electrical
• Telecommunications
• Tunnel and Private
• Premises 10 cm

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Design

• Tunnel Stability Surface Settlement Prevention
• Groundwater Measures
• New Urban Tunneling Method

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Tunnel Stability Surface Settlement Prevention

• Stabilization of Crown
• Stabilization of Cutting Face
• Foot Settlement

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Stabilization of Crown

• Forepiling
• Long Steel Pipe
• Jet Grouting
• Prevent collapse of face
• Restrict displacement ahead of face
• Steel Pipe Selected

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Stabilization of Cutting Face

• Shotcrete
• Jet Grouted Face piling
• Prevents collapse of cutting face

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Foot Settlement

• Establish Bottom Structure
• Anchor into Strong Stratum
• Transfer load from Crown Support

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Groundwater Measures

• Could cause blowout
• Two Methods
• Cutoff
• Drainage
• Horizontal Piping
• Extended Footpiles

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New Urban Tunneling Method
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Comparison to Alternative Method
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Comparison to Alternative Method
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Construction
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Measurement Results

• Ground Surface Settlement
• Building Tilt
• Groundwater

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Ground Surface Settlement
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Ground Surface Settlement
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Building Tilt

• Allowable Tilt 1.0/1000 rad
• Observed Tilt 0.5/1000 ? 0.8/1000 rad
• No building damage

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Groundwater
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Groundwater
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Groundwater
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Summary

• Ground Settlement Minimized
• Building Tilt Prevented
• Groundwater Drained

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Conclusions

• Tunneling has come a long way
• Continuously Evolving
• New Methods
• What will the future bring?

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Questions