tunnel lining may be permanent or temporary based upon their use and requirement. design of lining is done in two parts one is temporary or initial lining design and other is permanent design of the lining. empirical and theoretical methods are major design methods.

1. STRUCTURAL DESIGN OF
TUNNEL LINING
PRESENTED BY:
Mahesh Raj Bhatt
M.E. In Structural Engineering
Kathmandu University
31th march-2017

2. Content outline:
Team work in tunnel design
Fundamental approach of design
Lining in tunnel
Mode of failure in lining
Design of lining
Initial design
Final design
Conclusion

3. Team work in tunnel design:
i. Engineering Geologist: geo-exploration
ii. Hydraulics engineer: tunnel pressure, profile
iii. Structural engineer: lining type and material selection
iv. Geotechnical engineer: ground support requirement
v. Civil engineer: construction, location, layout
vi. Surveyor: maps, geometric frameworks
vii. Environmentalist: Environmental issues
viii.Construction engineer: construction issue
ix. Other experts: estimation, costing, quality expert etc.

4. Fundamental approach of design:
• Engineers promise that the structure will
neither suffer structurally nor collapse during
its projected lifetime.
• Design must be
• Safe
• Stable
• functional
• Possible failure modes should be analyzed.

5. Lining in tunneling:
Steps in structural design construction
• Excavation: Blasting / mechanical tools
• Initial ground support: safety during work
• Final ground support: structural safety
what is tunnel lining?
• timber, brick, concrete, or steel
supports erected in a tunnel to
maintain dimensions and safe
working conditions.
• And finally for permanent safety
of the system.

6. Mode of failure in tunnel
Can be categorized
i. Failure due to discontinuity: fault, joint, fold
ii. due to stratified rocks
iii. Rock fail by stress: squeezing, in fault zone, weak
and expansive soil in deeper zone.
iv. Fail by mineral control
v. Water pressure control: swalling
vi. Seismic effects
vii. Other permanent soil land displacement
viii.Failure in shortcrete
ix. Failure in rock bolt and dowel system etc.

7. Fig: tunneling in Rock stratification:

11. Design of lining
Types:
a) Design of initial support
 installed after excavation to support the
opening safely.
b) Design of final lining:
 to make the structural safety and stability

12. a) Design of initial support:
Based upon: how to select material for support
i. empirical method: Terzaghi (1946)
ii.Theoritical method/ analysis method
iii.Fundamental approach: based on potential
failure mode
i) Imperical method: (design of steel ribs)
-based on the experience
-terzagi (1946) gave written rule for selection based
on Rock loads and RQD-index of the rock.
(RQD=rock quality designation)=degree of joint in rock mass

13. •Skinner , Wickman, Tiedeman (1972)
• Gave Rock structure rating (RSR)
Rock type
Joint
Discontinuity
Fault
Fold
Orientation based

16. ii) Theoretical method:
It deals with design of
• rock bolts
•Dowels
•Shortcrete
•Steel ribs design
•Rock bolts: based on 3-D wedge analysis
•Shortcrete: to make immediate stiffness to excavated rocks
•Dowel: to support mass / and reduce deflection

18. Design of steel ribs:
• Bent I-section or H-section made circular (steel)
Ribs are
oriented to act
as arch action
which reduces
moment in the
section.

19. b) Design of final lining:
• Common options are:
•Un reinforced concrete
•Reinforced concrete
•Segmental concrete
•Steel backfill with concrete
•Concrete pipe with backfill
•Steel backfill with grout
Note: interaction between rock and lining material is
important to design the lining in tunneling.

20. • Unlined tunnel: water excess to rock
• Shot-crete: to provide ground support, hydraulics
• Un reinforced line : to protect rock exposure,
smoothen
• Reinforced line:
1-layer:temperature stress and shrinkage
Multi layer: swelling, squeezing, high stress
• Steel lining: when internal pressure > external pressure/
ground or ground water

23. Load cases for design:

24. Design requirements:
• Lining thickness: tmin>300 mm
Min cover>100mm
Guideline EM-1110-2-2104 for concrete cover
• concrete mix design:
•Most cases=M21 (21 mpa)
•Thin line =M35
•Segmental line=M42
•Reinforcement: 0.28% of X-section of line
0.4% for blast type tunneling
note: reinforce for crack control due to temperature/pressure
etc.

25. Lining for external water pressure:
• If P external water< P internal water
Than take
P ex=Pin ( because leakage increases
external pressure)
•if Tlining< R/10 (R-radius of tunnel)

26. •If T lining>R/10

27. Circular tunnel with internal pressure:
Concerns are mainly on
1)Rock lining interaction
2) estimation of lining leakage
1) Rock lining interaction
-thin shell equation ( radial displacement of lining)
-cylinder theory for thick lining

28. To find
radial
displacem
ent of
lining:

29. 2) Lining leakage estimation:

30. Lining for bending and distortion:

31. Note: moment and forces analysis must be done
using Finite element analysis tools

33. Design of steel liners:
• Amstutz (1970)
• Jacobson(1974)
• Vaughan (1956)
• Moore (1960) computer solution:
•To find the critical buckling
pressure .

35. Linear ring lining design: basic approach
• A liner ring is statically indeterminate.
• A one pass lining is designed for transport and erection
loads, loads during grouting, and ground loads
• For a circular ring of constant cross section
symmetrically loaded
the thrust at the crown C is

39. • Note: in ring segmental design all the analysis
procedure is same as like as parabolic/circular
arch.
• Based upon the fined analysis result rebar
must be designed .
(horizontal thrust/ shear / and moment are
governing parameters for the lining rebar
design)

40. CONCLUSIONS:
• Lining design should be safe , stable and
functional
• Lining type depend upon the property of the
interior rock or soil.
• To save the rock portion to be exposure, lining is
done.
• To give additional support to rock mass lining is
needed.
• There are various methods for lining design these
may be not structural sometime these may be
only based upon the constructional approach.

41. Thank you!!
THANK YOU!!
Tunnel spillway in
Kanogawa dam Japan

42. References:
• Engineering and design tunnel and shaft in rock, CECW-EG
Engineer Manual1110-2-2901 Department of the Army U.S. Army
Corps of Engineers Washington, DC 20314-1000
• TUNNEL ENGINEERING, 20 Lars Christian F. Ingerslev , Arthur
G. Bendelius Parsons Brinckerhoff New York, New York
• PRACTICAL TUNNEL, CONSTRUCTION Gary B. Hemphill PhD,
PE, JOHN WILEY & SONS, INC.