# 102343358-Guide-LTA-Tunnel-Lining-Design.pdf

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### (Contributed by Goh Kok Hun)

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### personal work.

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### Checklist – Step by Step Design Procedure

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### carrying ground loads can be satisfied easily by many linings.

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### i) Bolts for joints : Steel bolts to joint segments

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LTA Civil Design Division Guidelines For Tunnel Lining Design

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### Yield strength of steel

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### The uniform distributed radial component will only produce hoop thrust and the lining

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### ring

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LTA Civil Design Division Guidelines For Tunnel Lining Design

2

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### Typically, Table 2 shows the load combination consider in the design of LTA tunnels.

ULS (crack width) SLS (deflection) SLS

1 2 3 4 5 6 7 8 9 10 11 12 Load Factor = 1.4 and

1.6 √ √ √ √ √

Load Factor = 1.0 √ √ √ √ √ √ √

75kN/m2 Uniform

Surcharge √ √ √ √ √ √ √ √

Water Table at Ground

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LTA Civil Design Division Guidelines For Tunnel Lining Design

Water Table 3m Below

Ground Surface √ √ √ √ √ √ √

Full Section Moment

of Inertia √ √ √ √ √ √ √ √

Reduced Section

Moment of Inertia √ √ √ √

Short Term Concrete

Young's Modulus √ √ √ √ √ √ √ √

Long Term Concrete

Young's Modulus √ √ √ √

of 15mm on Diameter √ √

### installed immediately after the tunnel is excavated tends to overestimate the loads and

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### rigid. In addition, by means of interface elements, a small number of discontinuities can

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### joints. High level contact stresses due to joint geometry and ring build may cause

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LTA Civil Design Division Guidelines For Tunnel Lining Design

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### of spalling.

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### the erection equipment.

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### of elasticity by using the volume loss due to the construction of the second tunnel.

x y ro p First tunnel Second tunnel a b

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LTA Civil Design Division Guidelines For Tunnel Lining Design

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### = 0, ∴A = 0, u = B/r

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LTA Civil Design Division Guidelines For Tunnel Lining Design

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### remains unchanged.

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### check on the main design method.

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LTA Civil Design Division Guidelines For Tunnel Lining Design

Planning Of Tunnel Project

Function / Capacity to be given to Tunnel Specification/Code/Standard to be used Survey/Geology Alignment Plan / Profile Cross Section

Conditions (Thickness, Width, etc) Inner Diameter Model to Compute Member Forces Computation Of Member Forces Check Of Safety of Lining Computation Of Member Forces

Safe and Economical

Approval Execution of Construction Works Yes Yes No No

### Lining Design

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### e) Tensile strength

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### b) Heave

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LTA Civil Design Division Guidelines For Tunnel Lining Design

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### Annex B Typical Applications of Instrumentation in tunnelling (Figure 8.1

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### possible after excavation. Two essential measures highlighted by the ICE guide are:-

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### ensuing discussions would focus on NATM design and construction in soft ground.

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### the method & duration of the works.

Concept – Initial overview, decisions on

final shape and size

Engineering Analysis

Observe and monitor support

behaviour Confirm original design or

redesign for strengthening based on monitored results Continue

Construction

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LTA Civil Design Division Guidelines For Tunnel Lining Design

z

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### considerable influence on the stability number at collapse.

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LTA Civil Design Division Guidelines For Tunnel Lining Design

2

### sufficient lag between the two excavation faces.

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### Below shows some of the commonly used support measures in soft ground tunnelling.

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### the in-tunnel deformations & convergence that are instrumental in the monitoring of

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### considerations such as multiple tunnel construction in close proximity.

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### credible values to design for the allowable deformations, bending moments and

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LTA Civil Design Division Guidelines For Tunnel Lining Design

### conditions and lining performance.

Concept – Initial

overview, decisions on final shape and size

Initial support selection based on experience and

empirical methods Commence construction Observe and monitor support behaviour Strengthen/Amend support based on monitoring results Continue Construction

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## References

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