CIVE 1105 – ROCK MECHANICS The Northern Sewerage Project

CIVE 1105 – ROCK MECHANICS
The Northern Sewerage Project (NSP)

Course Coordinator: Dr. Gang Ren
NAME :LAU ZHI XIANSTUDENT ID :S3481975REPORT DUE : /05/2018
Table of Contents
Introduction………………………………………………………………………………………………3
Project Brief………………………………………………………………………………………………3
Factual Information Review..……………………………………..…………………………….4
Relevant Boreholes…………………………………………………….…………………………4
Area of interest..……………………………………………………….…………………………..4
Interpretation of the Borehole logs..……………………….……………………………4
Rock Mass Classification……………..……………………………..……………………………..8
RMR Classification System……………………………….……………………………………8
RMR Classification – Key assumptions………………………………………………9
Summary of RMR Rating.…………………………………………………..……………10
Rock Tunnelling Quality Index (Q-system).…………………….……………….…11
Q-system – Key assumptions..…………………………………………………………11
Summary of Q-System Rating………………………………………………………….12
Discussions of results…………………..……………………………….…………………………13
Recommendation from RMR Classification System………..……………..……13
Recommendation from RMR Q-System ……………………….……………..………15
Discussion………………….……………………………………………………………………………16
Deformation Modulus of Rock Mass……………………………………………………16
Final Recommendation……………………………………………………………………….17
References………………………………………………………………………………………………18
Appendixes………….……………………………………………………………………………………19
Appendix A – RQD Calculation…………………………………………………………….19
Appendix B – Calculation of Rating Adjustment….………………………………20
Appendix C – RQD Calculation ………………………………….…………..…………….22
Appendix D – Application of Result from Q-System……………………….……23
Introduction
Project Brief
The Northern Sewerage Project (NSP) is one of the largest, most complex wastewater tunning projects carried out in Australia, with the joint efforts of the two largest Victorian water authorities, Melbourne Water and Yarra Valley Water.

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With Melbourne experience unprecedented growth, the goal of this project is to provide a fully functioning metropolitan sewerage network that will contribute to overall public health system. The new sewer, once fully commissioned, will greatly increase the capacity of the existing system and provides capacity for the additional 70000 new homes across the Melbourne’s Northern growth corridor.

The project is particularly complex in location of the proposed tunnel alignment, which is situated in a challenging geological and site conditions, and in a dense urban environment. Running through eight suburbs, the project needs to work in close proximity of approximately 2500 private properties. One of the key challenges of this project is the unpredictable geological condition and the identification of suitable technology to perform excavation.

This assignment is mainly focused on the northern end of the tunnel alignment, with project area defined by borehole NIS-P3-214 and NIS-P3-219, located between Fawkner and Reservoir. The sewer tunnel is to be 2.2 metre in depth and has a 1:500 towards the North. The section of the tunnel alignment runs through residential properties and parkland. To understand the geological features of this site, a total of 9 boreholes were obtained and 4 boreholes analysed for the purposed for this project. These boreholes were chosen for their relevance in physical location and completeness of data.

The data obtained from four borehole logs along the tunnel alignment are used to perform the ground of the geological features using the Rock Mass Rating System (RMR) and the Rock Quality Tunnelling Index (Q-system).

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Figure SEQ Figure * ARABIC 1.1 : Location of all available boreholesFigure SEQ Figure * ARABIC 1.2: Boreholes in the section of interest
Factual Information Review
Relevant Boreholes
The boreholes initially selected for their idea geological locations were boreholes 214, 112, 220, 227 and 219. However, due to a lack of data for boreholes 112 and 227, they were omitted from the analysis. Borehole 181 was later adopted to substitute for 227. As borehole 181 is in close proximity with 227, this report reasonably assumed that the data can be used as an estimate in place for the lack of data for borehole 227.

The boreholes adopted for the final analysis included 214, 220, 181 and 219. The potential geological cross-section was developed using data obtained from the phase 3 Borehole logs report developed by Sinclair Knight Merz (SKM). The geological features of the cross-section along the tunnel alignment were interpolated from the borehole data. For the purpose of this analysis, borehole NIS-P3-214 is treated as the point zero (0) at chainage 0m; and the rest of the boreholes are relative distance from it. Due to the uneven surface level of where each borehole was taken, the cross-section features were developed taken into consideration the elevation of the surface level as well as the depth of the borehole. Table 2.1 summarises the chainage and surface level information regarding each of the relevant borehole.

Area of Interest
The tunnel to be constructed will be 2.2m in depth, with a gradient of 1:500 from borehole 214 to 219. The analysis of the tunnel construction project takes into consideration the ground condition 5m above the crown of the tunnel and 2.2m below the invert of the tunnel, making a total interest depth of 9.4m. Figure 2.1 is a schematic illustration of the arrangement.
Interpretation of the Borehole Logs
For the purpose of this analysis, borehole NIS-P3-214 is treated as the point zero (0) at chainage 0m; and the rest of the boreholes are relative distance from it. Due to the uneven surface level of where each borehole was taken, the cross-section features were developed taken into consideration the elevation of the surface level as well as the depth of the borehole. Table 2.1 summarises the chainage and surface level information regarding each of the relevant borehole.
As illustrated in Figure 2.2, the location where the tunnel alignment sits features 9 types of materials. These include top soil, silty clay, basalt, sandy clay, clay, siltstone, clayey sand, sandstone and sand. The topsoil occupies the first one to three metres, basalt occupied most of the 30m depth that the boreholes were drilled to. In fact, the area of interest sits in only one material, basalt, which is desirable as a main material.
Water table is assumed to be at the elevation of 75.9m, as specified in the factual information provided for NIS-P3-181. There are no water table information available in other borehole logs therefore water table is assumed to be at the same elevation for the entire section. For the purpose of this analysis, the purposed tunnel is situated completely below the water table.

The information compiled from the borehole logs are used in the ratings of the ground condition in the RMR and Q-systems.

Borehole Number Chainage (m) Approximate Elevation (m)
NIS-P3-214 0 76.6
NIS-P1-112 195.05 82.30
NIS-P3-220 305.09 82.33
NIS-P3-181 464.00 82.35
NIS-P3-219 698.89 85.12
Figure 2.1: Relevant Boreholes
Chainage 0 (NIS-P3-214)
195.05 (NIS-P1-112) 305.09 (NIS-P3-220) 464.00 (NIS-P3-181) 698.89 (NIS-P3-219)
Elev Depth* Elev Depth* Elev Depth* Elev Depth* Elev Depth*
Surface Level 76.6 0 82.3 0 82.3 0 83.4 0 85.1 0
Interest Level (top) 61.6 15 62.0 20.3 62.2 20.1 62.5 20.8 63.0 22.1
Crown Level 56.6 20 57.0 25.3 57.2 25.1 57.5 25.8 58.0 27.1
Invert Level 54.4 22.20 54.8 27.5 55.0 55.0 27.3 28.0 55.8 29.3
Interest Level Bottom 52.2 24.4 52.6 29.7 52.8 29.5 53.1 30.2 53.6 31.5
Table 2.2: Points of interest in elevation (m) and depth (m) Depth* is relative to surface level
Figure 2.1: Schematic illustration of the alignment cross-section
Figure 2.2: Geological cross-section derived from borehole logs
Rock Mass Classification
This assignment will utilise two types of rick mass classification system to assess the condition of the rock within the area of interest (5m above the tunnel, 2.2m of the tunnel and 2.2m below below the tunnel). The two types of systems deployed are Rock Mass Rating (RMR) system and the Rock Tunnelling Quality Index (Q-system).

RMR Classification System
The RMR system was first introduced by Bieniawski in 1976 as a means to generate a single rock mass classification. The system takes into consideration 5 basic parameters of rock characteristics, weighted by their magnitude of effects on the rock strength. The sum of the ratings for the five parameters is then adjusted for orientation of joints with respect to the tunnel.

The five basic input of the system are:
Intact Rock Strength UCS (15pts)
The strength of the intact rock measured as the uniaxial compressive strength (UCS) obtained from an uniaxial compressive test; or the point load strength index. This property of rock has the lowest contribution of 15% to the overall rating.

Drill core quality RQD (20pts)
The rock quality designation index (RQD) is a quantitative estimate of rock mass quality, defined as the percentage of intact core pieces longer than 100mm in the total length of core. This property of rock contributes 20% to the overall rating.
Spacing of discontinuities (20pts)
The spacing of discontinuities is a measure of the distance between one joint in the rock to another. The property of rock contributes 20% to the overall rating.

Groundwater Conditions (15pts)
Groundwater condition takes into consideration the effects of the presence of water on the overall strength of the rock mass, more specifically how it reduces the overall strength. This property contributes 15% to the overall rating.

The RMR system is used to provide a rough guideline on a number of engineering properties including:
Average stand-up time
Cohesion of rock mass
Deformation modulus
Internal Friction angle of rock mass

RMR Classification – Key Assumptions
Due to a lack of data from some relevant boreholes and unattainavle information, many assumptions had to be made during the process for calculating RMR values for the Northern Sewerage Project. Following outline some of the key assumptions taken:
The rating of the strength of rock takes into account the average strength of each test carried on the borehole sections. This may not be the best approach as some borehole had high level of varying strength, such as borehole 181 which had a UCS range of 32-240 MPa. However, to simplify the analysis process, this assignment took an average strength of UCS and point load index data.

The RQD is calculated by inspecting the borehole photos for pieces over 10cm, the summing those pieces to find the percentage of that over the total length of the core runs. The inspection process includes scaling the photos of borehole logs in AutoCad, the measure the pieces were physically measured. A summary of this calculation can be found in Appendix A.

The condition of discontinuities of each borehole was rated only according to the roughness of the joints as the others features such as persistence, aperture, gogue and the weathering condition were not available.

The groundwater information was not available for each borehole logs. Therefore, it is assumed that water table is at the elevation of 75.9m, as specified in the factual information provided for NIS-P3-181. The condition then assumed to be as “Wet” for whole of the interest area of excavation.

The calculation for the rating adjustment for joint orientation assumes that the strike was perpendicular to the dip direction for all the boreholes; the direction of drive for the tunnel was Northeast at an angle of 45o from the North. To work out the data for rating, the data of all joint orientation were collated to obtain the average dip direction. A full calculation can be found in Appendix B. Using Bieniawski (1989) Table that summarise the effects of joint strike and dip in tunnelling, a rating adjustment was obtained for each boreholes.

Summary of RMR Rating
Borehole NIS-P3-214 NIS-P3-220 NIS-P3-181 NIS-P3-219 Condition Rating Condition Rating Condition Rating Condition Rating
Strength of Rock Point Load Index (MPa) 0.9-1.5 3 1.85-2.02 5 2.44-7.68 7 1.58-3.5 4
UCS (MPa) 24.33-47 45-55 32-240 29-52 RQD (%) 88.44% 17 75% 13 80.52% 17 99.67% 20
Spacing of Discontinuities (m) 0.29% 9 0.483 10 1.166 10 0.486% 10
Conditions of discontinuities Slightly rough, slightly weathered 25 Slightly rough, slightly weathered 25 Slightly rough, slightly weathered 25 Slightly rough, slightly weathered 25
Groundwater Conditions* Wet 7 Wet 7 Wet 7 Wet 7
Rating Adjustment for Joint** Orientations Favourable -2 Favourable -2 Very favourable 0 Very favourable 0
RMR 59 58 66 66
Description Fair Fair Good Good
Average stand-up time 1 week for 5m span 1 week for 5m soan 1 year for 10m span 1 year for 10m span
Cohesion of rock mass (MPa) 0.2-0.3 0.2-0.3 0.3-0.4 0.3-0.4
Internal Friction angle of rock mass (o) 25-35 25-35 35-45 35-45
Deformation modulus (GPa) 18-5.6 18-5.6 56-18 56-18
*The condition is then assumed to be as “Wet” for whole of the interest area of excavation**Assuming that the strike is perpendicular to the tunnel axis, and the drive is with the dip.

Rock Tunnelling Quality Index (Q-system)
Proposed by Barton et al (1974), the rock tunnel quality index, Q-system was developed specifically to determine the rock mas characteristics and tunnel support requirement for underground excavation. The Q-rating is defined by the following equation:
Q=RQDJn×JrJa×JwSRFWhere RQD = Rock Quality Designation
Jn = Joint set number
Jr = Joint roughness number
Ja = Joint alteration number
Jw = Joint reduction factor
SRF = Stress reduction factor
RQDJn, the first quotient of the equation represents the structure of the rock mass.

JrJa, the second quotient of the equation represents the roughness and frictional characteristics of the joint wall or filling materials. Rougher surface with higher shear capacity is favourable in tunnel stability.

JwSRF, the third quotient is a complicated empirical factor describing the “active stress”.

Q-system – Key Assumptions
Due to a lack of data from some relevant boreholes and unattainable information, many assumptions had to be made during the process for calculating Q system values for the Northern Sewerage Project. Following outline some of the key assumptions taken:
RQD values were obtained from RMR. See Appendix A
The number of joint set was counted by visually inspecting the borehole logs. The estimation is based on the proximity of the discontinuities, the orientation (dip/dir) of discontinuities. For example, discontinuities that are similar orientation were considered to be part of the same joint set.

All joint wall were assumed to be “rough” for this analysis.

All joint wall were assumed to be unaltered, with surface staining only.

For joint water reduction, it is assumed that there is medium flow pressure, resulting in occasional outwash of joint fillings. This assumption was made as the whole of the interest are is below the water table.

The SRF was calculated for competent rock, using the formula?c?1, where ?c is the uniaxial compressive stress and ?1is the major principle stress. See Apendix C for full calculation.

Summary of Q-System Rating
Borehole NIS-P3-214 NIS-P3-220 NIS-P3-181 NIS-P3-219 Condition Rating Condition Rating Condition Rating Condition Rating
RQD Good 88.4 Fair 75 Good 80.5 Excellent 99.7
Joint Set Number (Jn)3 9 3 9 3 9 4 15
Joint Roughness Number (Jr)Rough 3 Rough 3 Rough 3 Rough 3
Joint Alternation number (Jw)*Unaltered 1 Unaltered 1 Unaltered 1 Unaltered 1
Joint Water Reduction factor (Jw)*Medium inflow or pressure occasional outwash of joint fillings 0.66 Medium inflow or pressure occasional outwash of joint fillings 0.66 Medium inflow or pressure occasional outwash of joint fillings 0.66 Medium inflow or pressure occasional outwash of joint fillings 0.66
Stress Reduction Factor Medium Stress 1 Medium Stress 1 Medium Stress 1 Medium Stress 1
Q- Value Good 19.45 Good 16.5 Good 17.71 Good 13.2
*The same assumption was made in the Q-system as the Bieniawaski’s RMR system, which is that ground is wet.

Discussions of Results
Recommendation from RMR Classification System
A total of 4 borehole logs were analysed and rated using the RMR classification system. Out of the four, two boreholes, 214 and 220 were rated “fair” and two others, 181 and 219, were rated “Good”. Each rating category indicates a set of important engineering properties in relation to average stand up time, a prediction for the cohesion of rock mass (MPa), internal friction angle of rock mass and the deformation modulus. Table 4.1 summarises the important engineering properties for the tunnel cross section determined from using the RMR rating system.

The following support recommendation is based on the assumption that the rock mass rating is fairly consistent across the whole length of the tunnel. To be more conservative in the support requirement, the support should be designed for fair rock along the whole length of the tunnel. The recommendation from this report is taken from the guidelines for excavation and support of 10m span rick tunnel by Bienawksi, 1989. However, it is important to note the tunnel for the Northern Sewerage project is only 2.2m in diameter, so the guideline could be more exhaustive than actually required.

According to the RMR rating system, and Bieniawski (1989) guidelines of excavation and support, the excavation will need to be benched 1.5-3m in advance before heading. The support system needs to commence immediately after each blast due to the low capacity in average stand-up time. A complete support system is to be adopted 10m from the face. The recommended rock bolts are 4m systematic bolts spaced at 1.5m-2m at both the crown and walls of excavation, paired with wire mesh at the crown. The crown will be reinforced with 50-100mm shotcrete and 30mm shotcrete to the sides. No steel sets are required. A summary of the recommendation is outlined in Table 4.2.

RMR Rating System
Rating Fair Good
Average stand-up time 1 week for 5m span 1 year for 10m span
Cohesion of rock mass (MPa) 0.2 – 0.3 0.3 – 0.4
Internal Friction angle of rock mass (o) 25 – 35 35 – 45
Deformation modulus (GPa) 18 – 5.6 56 – 18
Rock mass class Excavation Rock bolts Shotcrete Steel sets
II Good Rock Full face, 1-1.5m advance. Complete support 20m from face Locally, bolts in crown 3m long, spaced 2.5m with occasuibak wire mesh 50mm in crown where required None
III Fair Rock Top heading and bench 1.5-3m advance. Complete support 20m fro face. Systematic bolts 4m long, spaced 1.5-2m in crown and walls with wire mesh in crown. 50-100mm in crown and 30mm in sides None
Table 4.1 Rock mass classes and corresponding engineering properties (Bieniasksi,1989)Table 4.2 Summary of recommendations
Recommendation from Q-System
Of the four boreholes that were analysed, all boreholes had similar Q values, ranging from 13.2 to 19.4, and all fell in the rating “Good”. Borehole 219 had the lowest rating of 13.2. Therefore, the support requirement for the tunnel excavation will be designed using the rating of borehole 219.

Using the Estimated support categories based on the Q values, support requirement can be determined. Assuming that the tunnel had a consistent worst rating of 13.2, the tunnel is considered an excavation category and would also be assigned an excavation support ratio (ESR) value of 1.3. According to the estimated support categories, using the Q value of 13.2. See appendix D for more detailed breakdown of this derivation.

It is very unlikely that the tunnel could be excavated without any external support at all. The reason for such result from the Q-system could be due to that the chart is not suitable to provide very accurate information for small span tunnel such as the one in this project.

Alternatively, necessary support can also be found from the following:
L=2+0.15BESR(Barton et al. 1974)
Where L Length of rock bolts B Excavation width Max Span (unsupported) = 2 × ESR × Q0.4
Using the method above, the Northern Sewerage tunnel spanning 2.2m with an ESR value of 1.3 and with the lowest Q value of 13.2, will required rock bolts in length of at least 2.3m, and has a maximum unsupported span of 7.3m.

Discussions of Results
In 2001, Hudson and Harrison developed a formula that correlated the RMR and the Q-system using the following formula:
RMR = 9logeQ + 44
A calculation was conduction to compare the results between the three different systems. A summary of the results is outline in Table 5.1. Overall, the rating derived from the RMR system and the Q system was fairly consistent, with the Q system slightly more optimistic and the RMR system. Using the correlation formula it is revealed that the difference in RMR rating and Q system reduces as the rating increases. However, in general, it is observable that the RMR could be underestimating the rock strength characteristic while the Q-system overestimates it.

Borehole NIS-P3-214 NIS-P3-220 NIS-P3-181 NIS-P3-219
RMR Rating 59 58 66 66
RMR class Fair Fair Good Good
Q-value 19.4 16.5 17.1 13.2
Q-system class Good Good Good Good
RMR Rating (Hudson & Harrison) 70.6 69.2 69.55 67.22
RMR Class Good Good Good Good
Table 5.1
Deformation Modulus of Rock Mass
Borehole NIS-P3-214 NIS-P3-220 NIS-P3-181 NIS-P3-219
RMR 59 58 66 66
Q Value 19.4 16.5 17.1 13.2
Deformation Modulus (Bieniawksi, 1989) 18 16 32 32
Deformation Modulus (Serafim & Pereira, 1983) 16.79 15.85 25.12 25.12
Deformation Modulus (Grimstad & Brton, 1993) 32.20 30.44 30.82 28.01
Bienawski E = 2 × RMR – 100 GPa (for RMR > 50)Serafim & Pereira E = 10(RMR-10)/40 GPaGrimstad & Barton E = 25log10Q
Final Recommendation
After analysis using two rating system and comparison of results using correlation formulas, it is recommended that the excavation being performed using a tunnel boring machines rather than other excavation method such as blasting. Blasting is likely to result in damage in the rock mass and further reduces stability. Since the rating of the ground was “fair” and “good”, and additional to the tunnel being small in span (2.2m only), minimal support is required during the tunnelling process. However, to increase safety, it is recommended that rock bolts and wire cage are installed around the crown and the wall of tunnel, both surfaces of which should also be reinforced with shotcrete as specified in section 4.0.

Reference
Barton, N. a. L. J., 1974. Engineering classification of rock masses for the design of tunnel support. Rock Mech, 6(4), pp. 189-239.
Bieniawski, Z. T., 1989. Engineering rock mass classifications. New York: Wiley.

Filby, M. & lliott, D., 2013. Northern Sewerage Project: The Quiet Achiever. Online Available at: http://www.acaa.net.au/wp-content/uploads/2015/05/Northern-Sewerage-Technical-Paper 1.pdf Accessed 12 May 2018.

Grimstad, E. & Barton, N., 1993. Updating the Q-system for NMT. Proc. Int. Symp. On Sprayed Concrete. Norway: Norwegian Concrete Association.

Hartman, W. & Handley, M., 2001. The application of the q tunnelling quality index to rock mass assessment at impala platinum mine, s.1,: GeoHart Consultant.

Hudson, J. & Harrison, J., 1997. Engineering rock Mechanics: An introduction to the principles. Oxford: Pargamon.

Loset, F., 1992. Support needs compared at the Svartisen Road Tunnel. S.l.: Tunnels and Tunnelling.
Palmstrom, A. & Broch, E., 2006. Use and misuse of rock mechanics classification systems with particular reference to the Q-system. Tunnels and Underground Space Technology, 21 (1), pp. 575-593.

RocScience, n.d. Hoek E. Rock Mass Classification. Online Available at: https://www.rocscience.com/documents/hoek/corner/04 Rock mass classification Accessed 15 May 2018.

Serafim, J. & J.P., 1983. Consideration of the geomechanics classification of Beniawski. S.l.:s.n.

Appendixes
Appendix A – RQD Calculation
214 220 181 219
Depth Length Depth Length Depth Length Depth Length
15-15.75 0.275 14.9-15.75 0.21 14.05-15 0.127 13.80-14.50 0.428
0.258 0.69 0.112 0.312
15.75-16.65 0.105 15.75-16.5 0.116 0.265 14.50-15.43 0.407
0.832 0.66 0.402 0.526
16.66-17.25 0.163 16.50-17.25 0.244 15-15.95 0.877 15.43-16.00 0.204
0.142 0.23 0.119 0.404
0.138 0.15 0.386 16.00-16.88 0.89
17.25-18.00 0.109 0.199 16.85-17.8 0.479 16.88-17.50 0.315
0.602 17.25-17.95 0.625 0.149 0.398
18-18.75 0.433 17.95-18.75 0.376 17.8-18.7 0.453 17.50-18.45 0.262
0.344 0.345 0.475 0.735
18.75-19.65 0.361 19.35-20.25 0.628 18.7-19.7 0.421 18.45-19 0.212
0.266 0.294 0.438 0.262
20.25-20.95 0.497 20.25-20.95 0.148 0.14 0.119
0.256 0.153 19.7-20.6 0.258 19-19.99 0.345
20.95-21.75 0.428 21.75-22.6 0.26 0.554 0.65
0.236 0.602 20.6-21.55 0.899 19.99-20.5 0.263
0.187 22.6-23.35 0.222 21.55-22.45 0.278 20.5-21.19 0.141
21.75-22.4 0.345 0.182 0.334 0.557
0.292 0.218 0.328 21.19-22 0.363
22.40-23.25 0.23 23.35-23.9 0.455 23.45-24.35 0.183 0.405
0.23 0.239 0.629 0.12
0.21 23.9-25.75 0.691 24.35-25.25 0.175 22.0-22.93 0.557
23.25-23.85 0.152 0.2 0.122 0.395
0.13 0.174 22.93-23.5 0.39
0.342 0.233 23.5-24.25 0.206
23.85-24.75 0.607 0.447
0.106 24.25-25 0.216
0.218 0.579
24.75-25.5 0.257 25-25.83 0.196
0.306 0.686
0.148 25.5-26.25 0.131 0.243 0.181 0.189 Total length of core run 11.25 10.85 11.19 12.03
Sum of pieces over 10cm 9.949 8.137 9.01 11.99
RQD 88.44% 75.00% 80.52% 99.67%
Rating 16 13 16 20
Description Good Fair/Good Good Excellent
Appendix B – Calculation of Rating Adjustment
No. Depth (m) Difference (m) Dir Av Dir Dip Av Dip
Borehole 214
8 15.378 0.283 327 155.1 12 29.53
9 15.661 0.324 248 84 10 15.985 0.36 344 20 11 16.345 0.021 346 22 12 16.366 0.142 355 16 13 16.508 0.47 12 11 14 16.978 0.45 140 20 15 17.428 0.233 23 4 16 17.661 0.271 330 5 17 17.932 1.145 171 62 18 19.077 0.116 21 21 19 19.193 0.071 37 19 20 19.264 0.176 32 31 21 19.44 0.037 34 31 22 19.477 0.082 24 34 23 19.559 0.145 54 40 24 19.704 0.089 32 49 25 19.793 0.372 206 48 26 20.165 0.101 1 66 27 20.266 0.121 8 53 28 20.387 0.469 39 22 29 20.856 0.252 169 34 30 21.108 0.411 70 16 31 21.519 0.158 162 26 32 21.677 0.185 184 15 33 21.862 0.657 164 10 34 22.519 0.267 142 14 35 22.786 0.341 300 21 36 23.127 0.421 276 17 37 23.548 0.132 244 20 38 23.68 0.7 291 28 39 24.38 178 74 No. Depth (m) Difference (m) Dir Av Dir Dip Av Dip
Borehole 181
21 27.098 1.112 86 129.3 40 57.5
22 28.21 2.059 230 54 23 30.269 0.326 21 65 24 30.595 180 71 No. Depth (m) Difference (m) Dir Av Dir Dip Av Dip
Borehole 220
5 20.424 0.868 271 195.7 15 27.4
6 21.292 0.284 285 30 7 21.576 1.582 76 6 8 23.158 0.564 11 15 9 23.722 0.182 106 8 10 23.904 0.652 305 21 11 24.556 0.497 328 14 12 25.053 0.091 267 13 13 25.144 0.307 184 3 14 25.451 1.274 20 49 15 26.725 0.75 225 6 16 27.475 0.383 263 62 17 27.858 0.566 76 39 18 28.424 0.124 221 45 19 28.548 0.435 226 56 20 28.983 0.046 254 42 21 29.029 0.148 167 20 22 29.177 0.107 178 14 23 29.284 0.324 214 59 24 29.608 237 31 No. Depth (m) Difference (m) Dir Av Dir Dip Av Dip
Borehole 219
58 21.716 0.43 136 194.6 60 54.4
59 22.146 0.036 211 51 60 22.182 0.668 130 61 61 22.85 0.709 300 84 62 23.559 0.012 273 23 63 23.571 1.039 295 81 64 24.61 0.712 149 53 65 25.322 0.517 185 10 66 25.839 0.268 238 20 67 26.107 0.119 224 22 68 26.226 0.78 1 72 69 27.006 0.044 50 53 70 27.05 0.57 249 36 71 27.62 0.725 190 86 72 28.345 0.109 159 45 73 28.454 0.525 209 17 74 28.979 1.111 156 31 75 30.09 0.771 329 69 76 30.861 0.065 249 71 77 30.926 0.109 222 82 78 31.035 0.889 216 86 79 31.924 111 84 Strike perpendicular to tunnel axis Strike parallel to tunnel axis
Drive with dip Drive against dip Dip 45o-90o Dip 20o-45o Dip 45o-90o Dip 20o-45o Dip 45o-90o Dip 20o-45o Dip 0o-20o irrespective of strike
Very Favourable Favourable Fair Unfavourable Very Unfavourable Fair Fair
Table 3.6 The effects joint strike and dip in tunnelling (after Bieniawski, 1989)
Appendix C – Calculation of SRF
Boreholes 214 220 181 219
Uniaxial Compressive Stress (?c) (MPa)* 30.9 50 82.3 44
Depth to the base of the tunnel (m) 22.2 27.3 28 29.3
Unit Weight (kN/m3)** 24 24 24 24
Major Principle Stress (?1) (MPa) 0.53 0.66 0.67 0.70
?c?158.00 76.31 122.47 62.57
SRF*** 1 1 1 1
*Taken the average UCS of each borehole log**Assume Unit Weight of 24kN/m3***SRF values are obtained using the following table

Table 6: (cont’d.) Classification of individual parameters in the Tunnelling Quality Index Q (After Barton et al 1974)
Appendix D – Application of result from Q-system
Table D1 Estimated support categories
Rock Mass Quality, Q=RQDJn×JrJa×JwSRFREINFORCEMENT CATEGORIES:
Unsupported
Spot Bolting
Systematic Bolting
Systematic Bolting, (and unreinforced shotcrete, 4-10 cm)
Fibre reinforced shotcrete, 5-9 cm
Fibre reinforced shotcrete and bolting, 9-12 cm
Fibre reinforced shotcrete and bolting, 12-15 cm
Fibre reinforced shotcrete, ; 15 cm, reinforced ribs of shotcrete and bolting
Cast concrete lining
Excavation Category ESR
A Temporary mine openings. 3-5
B Permanent mine openings, water tunnels for hydro power (excluding high pressure penstocks), pilot tunnels, drifts and headings for large excavations. 1.6
C Storage rooms, water treatment plants, minor road and railway tunnels, surge chambers, access tunnels. 1.3
D Power stations, major road and railway tunnels, civil defence chambers, portal intersections. 1.0
E Underground nuclear power stations, railway stations, sports and public facilities, factories 0.8
Q Value 13.2
ESR 1.3
Span of tunnel 2.2
Span/ESR 1.69