This is a theses project done by Rodney Chiabi, 2019. It deals with "Optimization of tunnel reconstruction: case of a railway guage conversion". This theses had as aim the answer the questions: (1) How to efficiently execute tunnel reconstruction procedures; (2) How to maintain train circulation in the CAMRAIL tunnel; (3) How to reduce cost and construction time.

1. OPTIMISATION OF TUNNEL RECONSTRUCTION: CASE OF A
RAILWAY GAUGE CONVERSION
End of course thesis presented and defended by
RODNEY CHIABI NUH MIH
In partial fulfillment of the requirements for the award of a
MASTERS OF ENGINEERING IN CIVIL ENGINEERING
President : Pr. TAMO TATIETSE Thomas, Professeur titulaire des universités
Supervisor : Pr. LEZIN SEBA MINSILI, Maître de Conférences
Examiner : Pr. MANJIA MARCELINE, Maître de conférences UY1
Mémoire de fin d’études d’Ingénieur de
Conception de Génie Civil et Urbain
Before the Jury composed of:
10/10/2019 1

2. Présenté par RODNEY CHIABI NUH MIH 2
APPLICATION OF METHODOLOGY
METHODOLOGY
CONCLUSION AND PERSPECTIVES
PLAN DE L’EXPOSE
INTRODUCTION
CONTEXT AND PROBLEM STATEMENT
OPTIMISATION OF RETAINED SOLUTION

3. Présenté par RODNEY CHIABI NUH MIH 3
PLAN DE L’EXPOSE
INTRODUCTION

4. 4
GENERALITIES ON RAILWAY SYSTEMS
INTRODUCTION
The Railway Transport System is a key factor for the socio-
economic development of a nation, permitting the
traversing of distances that a too long to drive and too
short to fly.
A railway system is mainly characterized by its
• gauge which is the spacing that exists between the inner
faces of two parallel rail heads.
• Mode of operation which is the number of simultaneous
railway track between two locations.

5. 5
GENERALITIES ON RAILWAY SYSTEMS
INTRODUCTION
The Railway Gauge
The different gauges can broadly be divided into the following four
categories
 Broad Gauge: width 1676 mm to 1524 mm;
 Standard Gauge: width 1435 mm and 1451 mm;
 Metre Gauge: width 1067 mm, 1000 mm and 915 mm;
 Narrow Gauge: width 762 mm and 610 mm.

6. 6
GENERALITIES ON RAILWAY SYSTEMS
INTRODUCTION
Mode of Operation of a Railway
Here we distinguish single track and dual track.
• A single-track railway is a railway where trains traveling in both
directions between two locations share the same track.
• A double-track railway consists of a pair of tracks for both directions,
between two locations.

7. 7
GENERALITIES ON TUNNELING
INTRODUCTION
TUNNELING
At times tunnels may be necessary to allow the
railway line to overcome certain natural obstacles
along the railway axis such as mountains or water
bodies.

8. 8
GENERALITIES ON TUNNELING
INTRODUCTION
TUNNEL DESIGN APPROACHES
TUNNEL
DESIGN
EMPIRICAL
DESIGN
APPROACH
NUMERICAL
DESIGN
APPROACH
ANALYTICAL
DESIGN
APPROACH

9. 9
GENERALITIES ON TUNNELING
INTRODUCTION
TUNNEL EXCAVATION METHODS
TUNNEL
EXCAVATIO
N
TUNNEL BORING
MACHINE
MECHANISED
METHODS WITH
ROADHEADERS
DRILL AND BLAST For Hard rocks
For medium
Strength rocks
For Soft
Grounds

10. Présenté par RODNEY CHIABI NUH MIH
1
0
PLAN
CONTEXT AND PROBLEM STATEMENT

11. 1
1
CONTEXT AND PROBLEM
OVERVIEW
THE CAMEROON RAILWAY NETWORK
The Cameroon Railway network is a single-track system, built on
the metric gauge (1000 mm) which is the fruit of Cameroon’s
colonial heritage.
With the increase in the passenger and freight traffic, there has
been a growing need to modernize and expand the existing railway
network to meet the growing demand.
It is this light that the Cameroon National Railway Master Plan
(CNRMP) was proposed; which contains recommendations on the
modernization of the existing railway network.

12. 1
2
CONTEXT AND PROBLEM
CAMEROON NATIONAL RAILWAY MASTER PLAN
(CNRMP)
THE CAMEROON RAILWAY NETWORK
CNRMP
1. Conversion from
metric gauge to
standard gauge
2. Conversion from
Single Track to Dual
Track mode

13. 1
3
CONTEXT AND PROBLEM
PROBLEM STATEMENT
THE CAMEROON RAILWAY NETWORK
In this context the following questions arise:
 How To Efficiently Execute Tunnel
Reconstruction Procedures
 Maintaining Train Circulation In The
Tunnel
 Minimizing Interruptions
 Reduced Cost and Construction Time
With a change from metric to standard gauge,
and from single track to dual track mode, all
tunnels on the railway network would need to
be enlarged to allow for the new type of rolling
stock.

14. Présenté par RODNEY CHIABI NUH MIH
1
4
METHODOLOGY
PLAN DE L’EXPOSE

15. 15
METHODOLOGY
METHODOLO
GY
1. GENERAL SITE
SURVEY
2. OBSERVATION
3. TUNNEL DESIGN
PROPER

16. 16
METHODOLOGY
DATA
COLLECTION
Geometric Data
Morphology of the existing tunnel
• diameter,
• height,
• length
• shape
Topographic Data
• Longitudinal profile
• plane profile
• cross-section profile of the railway.
Geologic Data
• Color,
• texture,
• General state of fracture of the rock mass.
• Ground water inflow into the tunnel

17. 17
METHODOLOGY
METHOD ADOPTED FOR DESIGNING THE NEW
TUNNEL
EMPIRICAL
DESIGN
APPROACH
Based on :
 Uniaxial Compressive Strength (UCS), Point
Load Index and Schmidt Hardness
 Rock Quality Designation (RQD)
 Rock Mass Quality (Q)
 Rock Mass Rating (RMR)

18. 18
METHODOLOGY
1. UNIAXIAL COMPRESSIVE STRENGTH (UCS), POINT LOAD INDEX AND
SCHMIDT HARDNESS
Field Estimates of Uniaxial
Compressive Strength are
determined from the table below:

19. 19
METHODOLOGY
2. ROCK QUALITY DESIGNATION (RQD)
Rock quality designation (RQD) is a
rough measure of the degree of
jointing or fracture in a rock mass;
deduced from qualitative
observation of the rock mass.

20. 20
METHODOLOGY
3. ROCK MASS QUALITY (Q)
The rock mass quality (Q) is a very sensitive index whose numerical value
of Q varies on a logarithmic scale from 0.001 to a maximum of 1000. On the
basis of the value, nine categories exist for the classification of rock
masses

21. 21
METHODOLOGY
4. ROCK MASS RATING (RMR)
The Rock Mass Rating value is the sum of the values of the six parameters
as in the Equation below.
𝐑𝐌𝐑 = 𝐉𝐀𝟏 + 𝐉𝐀𝟐 + 𝐉𝐀𝟑 + 𝐉𝐀𝟒 + 𝐉𝐀𝟓 + 𝐉𝐁

22. 22
METHODOLOGY
Determination
of Rock Mass
Rating (RMR)

23. 23
METHODOLOGY
Determination
of Rock Mass
Rating (RMR)

24. 24
METHODOLOGY
Determination
of Rock Mass
Rating (RMR)

25. 25
METHODOLOGY
AVERAGE STAND-UP
TIME
The average stand-up time of the rock
mass was then deduced from the
graph below which gives the average
stand-up time of the rock mass
depending on the roof span and RMR
value.

26. 26
METHODOLOGY
1. Shape
1. Excavation Method
2. Structure Gauge
2. Size
GEOMETRIC DESIGN OF NEW
TUNNEL
CROSS-SECTION

27. 27
METHODOLOGY
1. Amount of Work to
be done
2. Construction
Cost
3. Construction
Duration
EVALUATION OF
QUANTITIES
EVALUATION

28. 28
METHODOLOGY
OPTIMAL
SOLUTION
SELECTION OF SOLUTION
EVALUATION
MULTI-
CRITERIA
COMPARISON

29. Présenté par RODNEY CHIABI NUH MIH
2
9
APPLICATION TO CASE STUDY
PLAN DE L’EXPOSE

30. 30
APPLICATION
CASE STUDY: SOUHE
TUNNEL
The SOUHE
tunnel found
along the Eseka
– Minloh
Maloume
segment of the
Transcam I
railway axis;
precisely
between PK 159
+ 375 to PK
161 + 395.

31. 31
METHODOLOGY
CASE STUDY: SOUHE
TUNNEL
GEOLOGIC
CHARACTERISATION

32. 32
APPLICATION
CASE STUDY: SOUHE
TUNNEL
POSSIBLE SOLUTIONS
1. Reconstruction And
Enlargement Of The Existing
Tunnel into dual track
2. Construction of an
adjacent Dual-Track
tunnel
3. Construction of an
adjacent Single-Track
tunnel
OPTIONS

33. 33
APPLICATION
CASE STUDY: SOUHE
TUNNEL
OPTION 1: RECONSTRUCTION AND ENLARGEMENT OF THE SOUHE
TUNNEL

34. 34
APPLICATION
CASE STUDY: SOUHE
TUNNEL
OPTION 2: CONSTRUCTION OF A NEW DUAL-TRACK TUNNEL
ADJACENT TO THE OLD TUNNEL

35. 35
APPLICATION
CASE STUDY: SOUHE
TUNNEL
OPTION 2: CONSTRUCTION OF A NEW SINGLE-TRACK TUNNEL
ADJACENT TO THE OLD TUNNEL

36. 36
APPLICATION
CASE STUDY: SOUHE
TUNNEL
EVALUATION OF OPTIONS
CONSTRUCTION COST
CONSTRUCTION
DURATION

37. 37
APPLICATION
CASE STUDY: SOUHE
TUNNEL
MULTI-CRITERIA
COMPARISON
Comparison By:
 Construction Cost
 Construction Duration
 Future Benefits
 Technical Feasibility

38. 38
APPLICATION
CASE STUDY: SOUHE
TUNNEL
OPTIMAL SOLUTION
OPTION 1

39. 39
APPLICATION
CASE STUDY: SOUHE
TUNNEL
OPTIMISATION OF THE
TUNNELING PROCEDURE

40. 40
APPLICATION
CASE STUDY: SOUHE
TUNNEL
OPTIMISATION OF THE
TUNNELING PROCEDURE
STAGE 1

41. 41
APPLICATION
CASE STUDY: SOUHE
TUNNEL
OPTIMISATION OF THE
TUNNELING PROCEDURE
STAGE 2

42. 42
APPLICATION
CASE STUDY: SOUHE
TUNNEL
OPTIMISATION OF THE
TUNNELING PROCEDURE
STAGE 3

43. 43
APPLICATION
CASE STUDY: SOUHE
TUNNEL
OPTIMISATION OF THE
TUNNELING PROCEDURE
STAGE 3

44. 44
APPLICATION
CASE STUDY: SOUHE
TUNNEL
OPTIMISATION OF THE
TUNNELING PROCEDURE
STAGE 4

45. 45
APPLICATION
CASE STUDY: SOUHE
TUNNEL
OPTIMISATION OF THE
TUNNELING PROCEDURE
STAGE 5

46. 46
APPLICATION
CASE STUDY: SOUHE
TUNNEL
OPTIMISATION OF THE
TUNNELING PROCEDURE
STAGE 6

47. 47
APPLICATION
CASE STUDY: SOUHE
TUNNEL
OPTIMISATION OF THE
TUNNELING PROCEDURE
STAGE 7

48. 48
APPLICATION
CASE STUDY: SOUHE
TUNNEL
OPTIMISATION OF THE
TUNNELING PROCEDURE
PROJECT DELIVERY

49. 49
APPLICATION
CASE STUDY: SOUHE
TUNNEL
ANALYSIS
New Austrian Tunnelling
Method (NATM):
 25,85 % savings in volume
of concrete required in the
support system.
10,28% reduction in
construction time

50. Présenté par RODNEY CHIABI NUH MIH
5
0
CONCLUSION AND PERSPECTIVES
PLAN DE L’EXPOSE

51. 51
CONCLUSION & PERSPECTIVES
CONCLUSION
This study demonstrated that the optimization of tunnel
enlargement, was practical, technically feasible and
economically viable solution for tunnel reconstruction.

52. 52
CONCLUSION & PERSPECTIVES
PERSPECTIVES
The in-depth analysis of a solution for a cost effective and
durable slab-track system,
that would be suitable for the railway tunnels in Cameroon.
The adaptation of the solution presented in this work to the
various tunnels on the
Cameroon railway network.
The numerical simulation of the proposed solution with
geotechnical data from a real
project to test actual performance of the system.
The actual implementation of this method on an actual
tunneling project.

53. Présenté par RODNEY CHIABI NUH MIH 53
Généralité : protections des
bétons
CONCLUSION