guidlines on the excavation process & support measures of

International Journal of Engineering Technology, Management and Applied Sciences

www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476

158 Dr. Hamed M. Jassim, Dr. Aomed A. Moh. Tokmachy,Hemn M. Omar

Guidlines On The Excavation Process & Support Measures Of

The Abandoned Haibat-Sultan Tunnel, Koya City, NE. Iraq

Professor, Dr. Hamed M. Jassim

#1, Assist. Prof. Dr. Aomed A. Moh. Tokmachy

## 2,

Assist. Lecturer Hemn M. Omar#3

#Koya University-Faculty of Engineering, Geotechnical Engineering Department

##Kirkuk University, College of Science, Applied Geology Department

ABSTRACT It is intended in this paper to use all the outcomes and results which were obtained from a previous paper which was

published by the same authors under the title of “ Characterization of rock mass units along the abandoned Haibat -

Sultan Tunnel “ for giving the guidelines of the tunnel excavation method and to predict the outlines of its support

measures and requirements.

The quality of the different rock mass units, selecting the excavation method and estimating the tunnel support

requirements were outlined by application of the two international rock mass classification and design systems, namely:

Rock Mass Rating (RMR) method and the Tunneling Quality Index (Q-system). According to these rock mass

classification systems and designs, the rock mass quality is classified to three categories: Category (I); very poor to

exceptionally poor rocks, Category (II); poor to fair rocks and Category (III); fair to good rocks, whereby about 75% of

the proposed tunnel length will go through very poor to exceptionally poor rocks, 18% will go through fair to good

rocks, and 7% will go through poor to fair rocks, so that the big percentage of the proposed tunnel length will go through

the bad quality rocks. Some relevant Conclusions and Recommendations for the most suitable tunnel excavation method ,

average stand-up time and the necessary support requirements for each rock mass units were outlined in this study.

Keywords

Rock mass classification systems, Rock Mass Rating (RMR), Tunneling quality index (Q-system), Excavation method,

Stand-up time, Rock mass units (RMU).

INTRODUCTION The previously proposed, and later abandoned Haibat-Sultan tunnel is located (4) km northeast of Koya city within Erbil governorate, Northern Iraq. It represents a part of Haibat Sultan Mountain series that is crossed by the Erbil – Sulaimania main road. It lies between latitudes (36° 06′ 00″– 36° 06′ 30″) North and longitudes (44° 39′ 31″ – 44° 40′ 12″) East, Fig. 1. The present road crossing Haibat Sultan Area represents a winding and curly state road with possible failures and rock falls along the road cut slopes, especially at the bedding planes on the southwestern side of the Mountain which have more possibility for sliding (Hamasur, 1991; Al-Saadi and Al-Jassar, 1993). These failures resulted in repeated closure of the road for hours, sometimes days, leading to major traffic jams and affecting road-based traffic. The proposed tunnel reduces all the driving dangers caused by rock falls, overturns and slippages in which the entry point (inlet) of this tunnel, with (730) m height above mean sea level, is located at the foot (SW side) of Haibat Sultan Mountain facing to Koya town but the exit point (outlet), with (760) m height, is located at the foot (NE side) of Haibat Sultan Mountain near Chnarok resort. This proposed tunnel has also an economic benefit in shortening the existing 4500 m long road in the area which represents the risky driving distance to only 900 m safe driving distance, whereby it will shorten the traveling time from Koya to Raniya, Sulaimania and other surrounding places considerably. In addition to these benefits, it has environmental advantages protecting and keeping resort's area compared to the old road. The aims of this study are to use the results and outcomes of the engineering geological and geotechnical studies, (Hamed, et. al., 2015), in order to assess the suitability of rock masses in the mountain for excavation of the tunnel by applications of both international rock mass classification systems; Rock Mass Rating (RMR) (Bieniawski, 1989) and Tunneling quality index (Q-system) (Grimstad and Barton, 1993; Barton, 2002).




Figure 1: Location and simplified topographic map of the study area (from Yilmazer, 2003)

1- BRIEF GEOLOGICAL SETTING The study area is located in the High Folded Zone of the Unstable Shelf Area. The high folded zone characterized by strong folding, orogenic uplift and possesses box-shape like and asymmetrical anticlines where some of them are associated with visible longitudinal faults and reverse faults are present along the steep limbs (Buday and Jassim, 1987; Jassim and Goff, 2006). The Haibat Sultan Mountain represents a homoclinal double plunging structure whereby the bedding planes are inclined regularly to the Southwest. The exposed formations along and around the section of the study area from older to younger are Kolosh, Khurmala, Gercus, Pilaspi and Fatha Formations, with approximate maximum thicknesses at the study area which are 290, 44, 114, 85 & 62 m, respectively, Fig. 2. Kolosh Formation (Paleocene – Lower Eocene) comprises the foot part at NE side of Haibat Sultan Mountain. The formation consists of very soft clastic rocks of green to dark grey coloured; marls, shales and thin horizons of sandstones. The upper contact of the formation with the overlying Gercus Formation is conformable, based on the first appearance of red mudstone which belongs to Gercus Formation. Khurmala Formation (Lower Eocene) forms small ridges at the foot NE side of Haibat Sultan Mountain. The formation consists of light grey colour, well bedded and hard fossiliferous limestone and dolomitic limestone. Some of them are interbedded with dark grey and soft clastic rocks of shale (Youkhana and Sissakian, 1986). Gercus Formation (Middle Eocene) forms steep slopes below the rocks of Pilaspi Formation at the upper part; NE side of Haibat Sultan Mountain. The formation consists of red to reddish brown clastic rocks which are mainly of mudstones (claystone & siltstones) and sandstones with some rare thin lenses of conglomerate. The upper contact of Gercus Formation with the overlying Pilaspi Formation is unconformable and marked by a conglomerate bed with (6) m thickness. Pilaspi Formation Upper Eocene forms continuous steep ridges at the crest of Haibat Sultan Mountain. The formation consists mainly of light grey and yellowish white colour, well-bedded and very hard limestones & dolostones. The upper contact of this formation with the overlying Fatha Formation is unconformable and is




marked by a conglomerate bed or may take the first appearance of mudstone belonging to the Fatha Formation. Fatha (Lower Fars) Formation Middle Miocene forms a continuous belt at the foot SW side of Haibat Sultan Mountain. The formation consists of cyclic deposits of (Mudstones and Limestones), with gypsum beds in the lower cycles.

Figure 2: A Geological map indicating the study area (from Sissakian, et al. 1993, 1997).

[

2- ASSESSMENT OF ROCK MASS UNITS ALONG THE TUNNEL AXIS As it was outlined and detailed in our previous research paper, ( Jassim, et al., 2015), 19 surface rock mass units were distinguished along the proposed tunnel axis and its surrounding area in Haibat Sultan Mountain, based on their engineering geological and geotechnical studies. These are presented here again in Figures 3 and 4. The RMR and Q values of each of the rock mass units are determined which indicate the quality of the rock masses. These systems were calculated by measuring the rating of the most abundant rock material, joint characteristics (parameters) and RQD-value of the rock masses with groundwater condition of the study area. Because of not having enough information about the groundwater of the study area, dry to wet as a general condition has been used to calculate the two systems. Also for applying these classification systems in highly fractured rock masses at the study area, the worst condition of non-applicable parameters (joint properties) have been used for calculation, Table 6 and Table 7. Also the excavation method and the stand-up time of the rock masses according to the RMR-system are determined. At last, support requirements of each of the rock masses are recommended. The D-shape and the 15 m diameter of the proposed tunnel with the value of (1.0) of the Excavation Support Ratio (ESR) for railway tunnels have been used to calculate the Q-value and determine the support requirements in the support chart related to the Q-system.




Figure 3: Geological cross-section of Haibat Sultan Mountain along the proposed tunnel axis

Figure 4: Geological cross-section and rock mass categories of Haibat Sultan Mountain along the

proposed tunnel axis

3- THEORETICAL BACKGROUND OF APPLIED GEOTECHNICAL CLASSIFICATION SYSTEMS Rock mass classifications are the means used extensively to quantitatively describe the quality of the rock mass and to estimate rock support requirements at pre-construction phases. There is a large number of rock mass classification systems developed for general purposes but also for specific applications, as listed in (Table 1). These different classification systems place different emphases on the various engineering geological and geotechnical parameters, and it is recommended that at least two methods must be used at any site during the early stages of a project (Hoek, 2007).




Table 1: Major rock mass classification systems (summarized from Edelbro, 2004; Palmstrom, 1995)

Remarks Form and Type

*) Applications

Country

of origin

Author and

First version

Name of

Classification

Unsuitable

for modern

tunneling

Description F

Behavior F,

Function T

Tunnels with

steel supports USA

Terzaghi,

1946 Rock Load Theory

Conservati

ve

Description F

General T Tunneling Austria Lauffer, 1958 Stand-up time

Utilized in

squeezing

ground

conditions

Descriptive F

Behaviouristic F,

Tunneling

concept

Tunneling in

incompetent

(overstressed)

ground

Austria

Rabcewicz,

1964/65 and

1975

The New Austrian

Tunneling

Method(NATM)

Unpublish

ed base

case

records

Numerical F,

Functional T

Tunnels, mines,

foundations etc.

South

Africa

Bieniawaski,

1974

Rock mass rating

(RMR-system)

Numerical F,

Functional T

Tunnels, large

chambers Norway

Barton et al.,

1974

Tunnelling quality

index (Q-system)

Descriptive F,

General T

For use in

communicat ion

Matula and

Holzer, 1978

The typological

classification

Descriptive F,

General T For general use - ISRM, 1981

Basic geotechnical

description (BGD)

Modified

RMR

Numerical F,

Functional T Sweden

Stille et al.,

1982

Rock mass strength

(RMS)

Numerical F,

Functional T Mines, tunnels -

Hoek et al.,

1995

Geological St rength

Index (GSI)

Stress-

free Q-

system

Numerical F,

Functional T India

Goel et al.,

1995

Rock mass Number

(N)

Numerical F,

Functional T

Rock

engineering,

communicat ion,

characterizat ion

Norway

Arild

Palmstrom,

1995

Rock mass index

(RMi)

*)Definit ion of the following expressions (Palmstrom, 1995)

Descriptive F = Descriptive Form: the input to the system is mainly based on descriptions.

Numerical F = Numerical Form: the input parameters are giving numerical ratings according to their

character.

Behaviouristic F = Behaviouristic Form: the input is based on the behaviour of the rock mass in a tunnel

General T = General Type: the system is worked out to serve as a general characterizat ion

Function T = Function Type: the system is structural for a special applicat ion (for example for rock support)

The following geotechnical classification systems are adopted in this work:

3.1- Rock Mass Rating (RMR) system ( or Bieniawsky’s system ) (or Geomechanics

Classification system) Bieniawaski in 1974 introduced the rock mass rating (RMR) system (also known as Geomechanics classification). This classification system has been modified and the last modification was made in 1989 (Bieniawaski, 1989). The following six parameters are used to classify a rock mass using the RMR system • Uniaxial compressive strength of rock material, UCS. • Rock quality designation (RQD). • Spacing of discontinuities. • Condition of discontinuities. • Groundwater conditions. • Orientation of discontinuities.




Applying this classification system, the rock mass is divided into a number of structural regions and each region is classified separately. The parameters above are rated according to (Table A-1) in Appendix. The summation of these parameters gives the RMR value between 0 and 100, where 100 is high quality intact rock and 0 is very poor rock. The RMR values are classified in five different classes in Table 2.

Table 2: Classification of RMR values Class no. RMR Rock Quality

I 81 – 100 Very good II 60 – 80 Good

III 41 – 60 Fair IV 21 – 40 Poor

V ˂ 20 Very poor

3.1.1- Stand-up time and RMR-classification system The stand-up time or bridging capacity is the time of remaining unsupported in a rock mass in a tunnel after excavation that it mainly depends on the magnitude of the stresses within the unsupported rock mass, which in their turn depend on its span, strength and discontinuities pattern. Bieniawaski has related his RMR-system to the stand-up time of an active unsupported span (Fig. 5).

Figure 5: RMR in relation to roof span and stand up time for tunnels (Bieniawski, 1989)

3.1.2-Using RMR-systems to select tunnel excavation methods and support requirements The conventional method of advancing a tunnel in hard rock is by full-face driving, in which the complete face is drilled and blasted as a unit. However, full-face driving should be used with caution where the rocks are variable. The usual alternatives are the top heading and bench method or the top heading method, whereby the tunnel is worked on an upper and lower section or heading (Bell, 2007). The sequence of operations in these three methods is illustrated in (Fig. 6).

Figure 6: Tunnelling by drilling and blasting, (a) Full-face, (b) top heading and bench, and (c) top heading. Bench

drilled horizontally. Phases: d = drilling; b = blasting; m = mucking; s = scraping (Bell, 2007)




The term support is widely used to describe the procedures and materials used to improve the stability and maintain the load-carrying capability of rock near the boundaries of underground excavations (Brady & Brown, 2005). Bieniawaski (1989) published a set of guidelines for the selection of excavation and support in tunnels in rock for which the value of RMR has been determined, (Table 3).

Table 3: Guidelines for excavation and support of 10 m s pan rock tunnels in accordance with the RMR

system (Bieniawski, 1989)

Steel sets Shotcrete

Rock bolts (20 mm

diameter, fully

grouted)

Excavation

Rock mass

class

Generally no support required except spot bolting Full face, 3 m advance.

I -Very good rock RMR: 81 – 100

None. 50 mm in crown where required.

Locally both in crown 3 m long spaced 2.5 m with occasional wire mesh.

Full face, 1 – 1.5 m advance. Complete support 20 m from face.

II- Good rock RMR: 61 – 80

None.

50 – 100 mm in crown and 3o mm in sides.

Systematic bolts 4 m long spaced 1.5 – 2 m in crown and walls with wire mesh in crown.

Top heading and bench 1.5 – 3 m advance in top heading. Commence support after each blast. Complete support 10 m from face.

III- Fair rock RMR:41 – 60

Light to medium ribs spaced 1.5 m where required.

100 – 150 mm in crown and 100 mm in sides.

Systematic bolts 4 – 5 m long, spaced 1 – 1.5 m in crown and walls with wire mesh.

Top heading and bench 1.0 – 1.5 m advance in top heading. Install support concurrently with excavation, 10 m from face.

IV- Poor rock RMR: 21 – 40

Medium to heavy ribs spaced 0.75 m with steel lagging and forepoling if required. Close invert.

150-200mm in crown and 150 mm in sides, and 50 mm on face.

Systematic bolts 5-6 m long, spaced 1-1.5 m in crown and walls with wire mesh. Bolt invert.

Multiple drifts 0.5 – 1.5 m advance in top heading. Install support concurrently with excavation. Shotcrete as soon as possible after blasting.

V-Very poor rock RMR: < 20

3.2- Tunneling quality index (Q-system) (or Barton’s system) (or N.G.I. system) The NGI tunnel quality index also known as the Q method is a numerical description of the rock mass quality with respect to tunnel stability. On the basis of an evaluation of large number of case histories of underground excavations Barton, Lien and Lunde developed the Q method. The Q value is defined by a function consisting of six parameters which may be estimated either from geological mapping or from in situ measurements. The Q method is used internationally for general description of the rock mass quality and as a guide for estimating tunnel support requirement (Løset, 1983). The Q value is a numerical description of the rock mass quality with regards to tunnel stability. The value varies on a logarithmic scale from 0,001 to a maximum of 1000. On the basis of the Q-value, the rock mass has been classified into nine categories, (Table 4).




Table 4: Classification of rock mass based on Q-values (Barton, et al., 1974)

Q- value Rock Quality Class 400 – 1000 Exceptionally good

A 100 – 400 Extremely good 40 – 100 Very good

10 – 40 Good B

4 – 10 Fair C 1 – 4 Poor D

0.1 – 1 Very poor E 0.01 – 0.1 Extremely poor F

0.001 – 0.1 Exceptionally poor G

The Q value is expressed as following: SRF

Jw

Ja

Jr

Jn

RQDQ , where the parameters are:

RQD is rock quality designation, is an index to assess rock quality quantitatively from drill core logs which are related to the degree of joints. It is defined as the percentage of intact core pieces longer than 100 mm in the total length of core (Deer, 1963). RQD has values from zero to 100. The Q function specifies that the value 10 is the lowest RQD value used. Jn is the joint set number. The joint set number takes values from 0,5 for massive rocks with no or few jo ints, to 20 for crushed rocks. Jr is the joint roughness number. The joint roughness number varies from 0,5 for slickenside, planar joints to 4 for discontinuous joints. Usually the value for the weakest significant joint is used in the Q function. Ja express the joint alteration number. The alteration number varies from 0,75 for unaltered joint walls to 20 for rock with thick, continuous zones of swelling clay. In the Q function the weakest or most unfavourable joint set is generally used. Jw stands for the joint water reduction factor. The joint water reduction factor takes the values from 1 for dry excavations to 0,05 for excavations with exceptionally high inflow. SRF is the stress reduction factor. The stress reduction factor has values from 1 for medium rock pressure to 20 for heavy rock pressure. The values are taken relative to the rock strength. The Q function may be considered as the product of the three quotients. The first quotient, RQD/Jn, is a measure for the relative block size. The second quotient, Jr/Ja, is a fair approximation to the actual inter block shear strength. The third quotient, Jw/SRF, describes the active stress. It is generally agreed that these three quotients represent three major parameters affecting the tunnel stability (Løset, 1983). In Appendix (Table A-2) the rating of the parameters is clarified.

3-2-1- Using the Q-system to evaluate support requirements In order to relate the Q-value to the support requirements of underground excavation, (Barton, et al. , 1974) defined an additional parameter, which they called the Equivalent Dimension, De, of the excavation. This dimension is obtained by: dividing the span, diameter or wall height of the excavation by a quantity called the excavation support ratio, ESR.

Hence: (ESR) RatioSupport Excavation

(m)height or diameter span, ExcavationDe The excavation support ratio (ESR) reflects the

degree of safety and support required for the underground opening, while safety considerations will depend on how the underground opening will be used. According to NGI (1997) the value of ESR varies from 5 to 0.5 depending upon the type of underground excavation, a low ESR-value indicates the need for a high level of safety while higher values indicate that a lower level of safety will be acceptable. Table (5) shows the values of ESR.




Table 5: The various values of ESR according to NGI (1997)

ESR Type of Excavation 3 – 5 Temporary mine openings, etc. A

2.5 2.0

Vertical shafts: i)circular sections ii) rectangular/square section

B

1.6 Permanent mine openings, water tunnels for hydro power (exclude high pressure penstocks), pilot tunnels, drifts and headings for large openings

C

1.3 Storage rooms, water treatment plants, minor road and railway tunnels, surge chambers, access tunnels, etc.

D

1.0 Power stations, major road and railway tunnels civil defense chambers, portals, intersections, etc.

E

0.8 Underground nuclear power stations, railway stations, sports and public facilitates, factories, etc.

F

0.5 Very important caverns and tunnels with a long lifetime, tunnels for gas pipe lines.

G

The equivalent dimension, De, together with the Q-values is used to define a number of support categories by plotting them in a chart published in the original paper by (Barton, et al. , 1974). This chart was updated by (Grimstad & Barton, 1993). Figure (7) shows this updated chart.

Figure 7: Estimated support categories based on the tunneling quality index Q (Grimstad & Barton, 1993)

As a result of processing the collected data and the available information, elaborated engineering geological descriptions of rock masses at the surface outcrops of the proposed tunnel axis, RMR and (Q) classification systems have been implemented whose results are shown in Table 6 and Table 7, respectively. Accordingly, and based on such details, the rock mass quality is classified to three categories: Category (I); very poor to exceptionally poor such as in (RMU-9, 10, 12, 14, 15, 16, 18 and RMU-19), Category (II); poor to fair such as




in (RMU-1 and RMU-2) and Category (III); fair to good such as in (RMU-3, 4, 5, 6, 7, 8, 11, 13 and RMU-17).

Table 6: Rock mass classification of the rock mass units along the proposed Haibat Sultan Tunnel

according to the RMR-system

Rock

Mass

Quality

Ratings

Thickness

along the

tunnel

axis (m)

Formation

RMU-

No. RMR-

value

Orientation of

discontinuities

Discontinuity

condition*

Groundwater

condition

Spacing of

discontinuities

RQD

Rating

UCS

Fair 58 0 23 15 8 8 4 53 Fatha 1(inlet)

Fair 47 -2 10 15 9 8 7 7 Fatha 2(inlet)

Good 73 0 24 7 13 17 12 25 Fatha 3

Good 76 0 25 7 12 20 12 7 Pilaspi 4

Good 74 -2 25 7 12 17 15 18 Pilaspi 5

Good 74 0 26 7 12 17 12 7 Pilaspi 6

Good 76 -2 23 7 12 20 15 15 Pilaspi 7

Good 75 -2 26 7 12 20 12 30 Pilaspi 8

Very

poor 17 -12 2 7 5 3 12 40 Pilaspi 9

Very

poor 14 -12 4 7 5 3 7 7 Pilaspi 10

Good 63 0 22 7 9 13 12 18 Pilaspi 11

Very

poor 7 -12 2 7 5 3 2 100 Gercus 12

Fair 56 0 23 7 9 13 4 10 Gercus 13

Very

poor 9 -12 2 7 5 3 4 40 Gercus 14

Very

poor 12 -12 2 7 5 3 7 100 Kolosh 15

Very

poor 12 -12 2 7 5 3 7 63 Kolosh 16

Good 75 -2 26 7 12 20 12 30 Khurmala 17

Very

poor 16 -12 2 7 9 3 7 300 Kolosh 18

Very

poor 9 -12 2 7 8 3 1 30 Kolosh

19

(outlet)

* It is the collective ratings of persistence, roughness, aperture, infilling materials and weathering state of the discontinuities.

Table 7: Rock mass classification of the rock mass units along the proposed Haibat Sultan Tunnel

according to the Q-system

Rock

Mass

Quality

Ratings

Thickness

along the

tunnel

axis (m)

Formation

RMU-

No. Q-

value SRF Jw Ja Jr Jn RQD

Poor 1.22 2.5 – 1

1.00 1 2 2×(15) 32 53 Fatha 1(inlet)

Poor 1.26 2.5 – 1

1.00 2 3 2×(15) 44 7 Fatha 2(inlet)

Fair 4.8 2.5 – 1

0.5 1 3 15 84 25 Fatha 3

Fair 6.09 2.5 – 1

0.5 1 2 9 96 7 Pilaspi 4

Fair 4.17 2.5 – 1

0.5 1 3 15 73 18 Pilaspi 5

Fair 4.22 2.5 – 0.5 1 3 15 74 7 Pilaspi 6




1

Fair 5.25 2.5 – 1

0.5 1 3 15 92 15 Pilaspi 7

Fair 8.66 2.5 – 1

0.5 1 3 9 91 30 Pilaspi 8

Except. poor

0.0025 10 0.5 10 1 20 10 40 Pilaspi 9

Except. poor

0.006 7.5 0.5 10 2 20 10 7 Pilaspi 10

Fair 4.19 2.5 – 1

0.5 1 2 9 66 18 Pilaspi 11

Except. poor

0.0016 10 0.5 15 1 20 10 100 Gercus 12

Fair 8.13 0.5 – 2

0.5 1 3 9 61 10 Gercus 13

Except. poor

0.0015 10 0.5 16 1 20 10 40 Gercus 14

Except. poor

0.0015 10 0.5 16 1 20 10 100 Kolosh 15

Except. poor

0.0025 10 0.5 10 1 20 10 63 Kolosh 16

Fair 8.75 2.5 – 1

0.5 1 3 9 92 30 Khurmala 17

Except. poor

0.0025 10 0.5 10 1 20 10 300 Kolosh 18

Except. poor

0.001 10 0.66 16 1 2×(20) 10 30 Kolosh 19 (out let)

4- RESULTS The characterization and applying the RMR and Q classification systems of nineteen rock mass units at the study area and the relevant geotechnical parameters which were obtained from our previous research paper, [12] have been used in the design concept of the RMR and Q systems. The rock material and the discontinuity properties of the rock masses were described and characterized as shown in Table 8 for both classification systems and the recommended tunnel excavation method and the support measures required were outlined in the same table.

5- CONCLUSIONS The following conclusions have been reached as an outcome of this study: 1- Since the strike of the bedding planes is perpendicular to the tunnel axis and the dip angle is at (40°– 50°) towards the tunnel, there is a likelihood of interference of water that may flow into the tunnel through the bedding planes. 2- Generally, bedding planes are perpendicular to the trend of the abandoned tunnel axis which is very favorable for excavation. This is enhanced by the nonexistence of any major structural disturbances such as faults and shear zones along the tunnel axis. 3- The fall and slide of unstable blocks in regularly jointed rock masses can be considered conservative since the size of blocks, formed in rock masses, will be limited by the persistence and the spacing of joints. 4- Because of the non presence of boreholes to obtain the underground actual information of regular and heavily jointed rock masses from actual core samples, the worst condition of discontinuity properties, RQD-value and the intact rock strength of these rock masses have been used in calculating the Q-system and Rock




Mass Rating (RMR) method. In this case the recommended support requirements will have an implicit safety factor which will put us on the safe side when constructing the tunnel and estimating its support requirements. 5- According to the RMR and Q classification systems, the rock masses are classified to three categories: Category I; very poor to exceptionally poor quality such as in (RMU-9, 10, 12, 14, 15, 16, 18 and RMU-19), Category II; poor to fair quality such as in (RMU-1 and RMU-2) and Category III; fair to good quality such as in (RMU-3, 4, 5, 6, 7, 8, 11, 13 and RMU-17). About 75% of the proposed tunnel length will go through very poor to exceptionally poor rocks, 18% will go through fair to good rocks, and 7% will go through poor to fair rocks so that the big percentage of the proposed tunnel length will go through the bad quality rocks. 6- According to the RMR-system, the average stand-up time after excavation of rock masses in category (I); very poor to exceptionally poor is 30 minutes for 1 m span, it is 10 hours to 1 week for 2.5 – 5 m span of rock masses in category (II); poor to fair rock, and it is 1 week to 1 year for 5 – 10 m span of rock masses in category (III); fair to good rock. 7- It has been proved that the application of the RMR and Q systems as rock mass classification schemes underground is easy in case of availability of the necessary geotechnical data.

6- RECOMMENDATIONS Based on the outcomes of this study, the following recommendations have been suggested: 1- Great care will be required to excavate and face-protect the two portal areas (inlet and outlet) because of their steep slopes and poor quality of the rocks. 2- Because of limited stand-up times of the rocks, the support must be carried out before the end of these times corresponding to the span of excavation, especially in the rocks of category (I); very poor to exceptionally poor, which represents a big percentage of the proposed tunnel axis. 3- The support systems and excavation guide methods were outlined in accordance with the recommendations of both (RMR) and (Q) classification systems, as presented in Figure 8 and Table 8. In this table, support requirements and excavation guide methods are simply assembled within three categories of the rock mass quality: Very poor to exceptionally poor; RMR (< 20) / Q (0.001 – 0.01, Poor to fair; RMR (41 – 60) / Q (1 – 4) and Fair to good; RMR (61 – 80) / Q (4 – 10). 4- It is recommended to combine the RMR and Q systems with other empirical methods for the determination of excavation method and support requirements in future studies.

Figure 8: Support requirements of the Rock Mass Units at the study area according to the Q-system

support chart.




Table 8: RMR ( Bieniawski, 1989) and ( Q ) ( Barton, et al., 1974; Grimstad & Barton, 1993 ) Support

Recommendations and Excavation Methods Guides for the rock mass units along the proposed Haibat

Sultan Tunnel

Support recommendations

Guide for

excavation

method (RMR)

RMU-No.

Rock mass quality;

RMR-value range/

Q-value range

Q-system RMR

Rock bolts 3 – 5 m long, spaced < 1 m and cast concrete lining.

Fully grouted (20 mm diameter) systematic rock bolts 5 – 6 m long, spaced 1 – 1.5 m in crown and walls with wire mesh, bolt invert. Medium to heavy ribs spaced 0.75 m with steel lagging and forepoling if required close invert. Shotcrete 150 – 200 mm in crown, 150 mm in sides, and 50 mm on face.

Multiple drifts 0.5 – 1.5 m advance in top heading, install support concurrently with excavation, shotcrete as soon as possible after blasting.

RMU-9, RMU-10, RMU-12, RMU-14, RMU-15, RMU-16, RMU-18 and RMU-19

Very poor to exceptionally poor; RMR(< 20)/ Q (0.001 – 0.01)

Rock bolts 3 – 5 m long, spaced 1.5 – 1.7 m and fibre reinforced shotcrete in 5 – 6 cm thickness.

Fully grouted (20 mm diameter) systematic rock bolts 4 m long, spaced 1.5 – 2 m in crown and walls with wire mesh in crown. Shotcrete 50 – 100 mm in crown and 30 mm in sides.

Top heading and bench 1.5 – 3 m advance in top heading; commence support after each blast, complete support 10 m from face.

RMU-1& RMU-2

Poor to fair; RMR (41 – 60)/ Q (1 – 4)

Rock bolts 3 – 5 m long, spaced 2.1 – 2.3 m and fibre reinforced shotcrete in 4 – 10 cm thickness.

Locally, Fully grouted (20 mm diameter) systematic rock bolts in crown 3m long, spaced 2.5 m with occasional wire mesh. Shotcrete 50 mm in crown where required.

Full face, 1 – 1.5 m advance, complete support 20 m from face.

RMU-3, RMU-4, RMU-5, RMU-6, RMU-7, RMU-8, RMU-11, RMU-13 and RMU-17

Fair to good; RMR (61 – 80)/ Q (4 – 10)




7- REFERENCES [1] Barton, N., 2001: Water and stress are fundamental to rock mass characterization and classification, Letter

to the Editor, ISRM News Journal, 4 p. [2] Barton, N., 2002: Some new Q-value correlations to assist in site characterization and tunnel design,

International Journal of Rock Mechanics and Mining Sciences, Vol. 39, pp. 185-216. [3] Barton, N., Lien, R. and Lunde, J., 1974: Engineering classification of rock masses for the design of

tunnel support, Rock Mechanics, Vol. 6, No. 4, pp. 189-236. [4] Bell, F. G., 2007: Engineering geology (2

nd ed.), Elsevier, Amsterdam, 581 p.

[5] Bieniawski, Z. T., 1989: Engineering rock mass classifications, Wiley, New York, 251 p. [6] Brady, B. H. G. and Brown, E. T., 2005: Rock mechanics for underground mining (3

rd ed.), Kluwer

Academic Publishers, New York, 628 p. [7] Deer, D. U., 1963: Technical description of rock cores for engineering purposes, Felsmechanik and

Ingenieurgeologie, Vol. 1, No. 1, pp. 16-22. [8] Edelbro, C., 2004: Evaluation of rock mass strength criteria, Licentiate Thesis, Lulea University of

Technology, Lulea, 98 p. [9] Grimstad, E. and Barton, N., 1993: Updating of the Q-system for NMT, Proceedings of the International

Symposium on Sprayed Concrete, Norwegian Concrete Association, Oslo, pp. 46-66. [10] Grimstad, E. and Barton, N., 1993: Updating of the Q-system for NMT, Proceedings of the International

Symposium on Sprayed Concrete, Norwegian Concrete Association , Oslo, pp. 46-66. [11] Hamasur, G.A., 1991: Engineering geological study of rock slope stability in Haibat-Sultan area,

North-East Iraq, M.Sc. Thesis, University of Salahaddin, College of Science, Iraq, 153 p. (In Arabic). [12] Hamed M. Jassim, Aomed A. Moh. Tokmachy, Hemn M. Omar, 2015: Characterization of Rock Mass

Units Along The Abandoned Haibat Sultan Tunnel, Koya City, NE. Iraq, International Journal of Engineering Technology Management and Applied Sciences ( IJETMAS ), Volume 3, Issue 3.

[13] Hoek, E. (2007) Practical rock engineering – course notes by Evert Hoek. http://www.rocscience.com/hoek/pdf/Practical_Rock_Engineering.pdf. 312p.

[14] Hoek, E., 1982: Geotechnical consideration in tunnel design and contract preparation, 17 th SirJulius Werhner Memorial Lecture, Trans. Inst. Min. Metall., Vol. 91, pp. A 101-A 109.

[15] Løset, F.: “The Q-Method and its Application-A Method for Describing Rock Mass Stability in Tunnels”. Norwegian Tunnelling Technology, publication no.2. 1983, 76-78.

[16] Milne, D., Hadjigeorgiou, J. and Pakalnis, R., 1998: Rock mass characterization for underground hard rock mines, Tunnelling and Underground Space Technology, Vol. 13, No. 4, pp. 383-391.

[17] Norwegian Geotechnical Institute (NGI), 1997: Practical method of the Q-method, NGI report: 592046-4, 44 p.

[18] Palmstrom, A., 1995: RMi – a rock mass characterization system for rock engineering purposes, Ph.D. Thesis, University of Oslo, 400 p.

[19] Robinson, C.S., 1972: Prediction of geology for tunnel design and construction, Proceeding Rapid Excavation and Tunnelling Conference, Chicago (eds K. S. Lane and L. A. Garfield), AIME, New York, pp. 105-114.

[20] Sissakian, V., Maala, K., Dlekran D., and Salman B. 1997. Geological Map of Arbeel and Mahabad Quadrangle. Sheet NJ-38-14 and NJ-38-15. state establishment of geologic survey and mining. Baghdad: Geosurv.

[21] Sissakian, V., Maala, K., Hamza N., Mahdi A., and Mohamad S. 1993. Geological Map of Kirkuk Quadrangle. Sheet No. NI-38-2. state establishment of geologic survey and mining . Baghdad: Geosurv.

[22] Zenobio, A. A. and Zuquette, L. V., 2004: RQI (" Rock Quality Index"): proposal for the correction of R. Q. D. parameter for natural rock slopes – Serra de Ouro Preto (Minas, Gerais, Brazil), Landslides: Evaluation and Stabilization, Ehrlich, Fontoura & Sayao (eds), Taylor & Francis, London, pp. 817-820.

8- APPENDICES : The core details and parameters of the two adopted classification and design systems are shown and illustrated in the following two tables:

http://www.rocscience.com/hoek/pdf/Practical_Rock_Engineering.pdf




Table A-1 : Details of Rock Mass Rating System (After Bieniawski, 1989) A. CLASSIFICATION PARAMETERS AND THEIR RATINGS

Parameter Rating of values

1

Strength of

intact rock material

Point-load

strength index ˃ 10 MPa 4 – 10 MPa 2 – 4 MPa 1 – 2 MPa

For this low range

uniaxial compressive test is preferred

Uniaxial comp.

strength > 250 MPa 100 – 250 MPa 50 – 100 MPa 25 – 50 MPa

5 - 25

MPa

1 –

5 MPa

˂ 1

MPa

Rating 15 12 7 4 2 1 0

2 Drill Core Quality RQD 90 % - 100 % 75 % - 90 % 50 % -75 % 25 % - 50 % ˂ 25 %

Rating 20 17 13 8 3

3 Spacing of discontinuities ˃ 2 m 0.6 – 2 m 200 – 600 mm 60 – 200 mm ˂ 60 mm

Rating 20 15 10 8 5

4

Condition of discontinuities

(See E)

Very rough

surfaces

Non continuous

No separation Unweathered

wall rock

Slightly rough

surfaces

Separation ˂1mm

Slightly weathered walls

Slightly rough

surfaces

Separation ˂ 1mm

Highly weathered walls

Slickensided

surfaces or

Gouge ˂ 5 mm

thick or separation 1-5 mm

Continuous

Soft gouge ˃ 5 mm

thick or

Separation ˃ 5 mm Continuous

Rating 30 25 20 10 0

5

Ground

water

Inflow per 10 m tunnel length (l/m)

Non ˂ 10 10 - 25 25 - 125 ˃ 125

(Joint water

press)/(Major principal σ)

0 ˂ 0.1 0.1 – 0.2 0.2 – 0.5 ˃ 0.5

General conditions Completely dry Damp Wet Dripping Flowing

Rating 15 10 7 4 0

B. RATING ADJUSTMET FOR DISCONTINUITY ORIENTATIONS (See E)

Strike and dip orientations Very favourable Favourable Fair Unfavourable Very unfavourable

Ratings

Tunnels & mines 0 -2 -5 -10 -12

Foundations 0 -2 -7 -15 -25

Slopes 0 -5 -25 -50

C. ROCK MASS CLASSES DETERMINED FROM TOTAL RATINGS

Rating 100 81 80 61 60 41 40 21 ˂ 21

Class number I II III IV V

Descriptions Very good rock Good rock Fair rock Poor rock Very poor rock

D. MEANING OF ROCK CLASSES

Class number I II III IV V

Average stand-up time 20 yrs for 15 m

span

1 year for 10 m

span

1 week for 5 m

span

10 hrs for 2.5 m

span 30 min. for 1 m span

Cohesion of rock mass (kPa) ˃ 400 300 - 400 200 - 300 100 - 200 ˂ 100

Friction angle of rock mass (deg) ˃ 45 35 - 45 25 - 35 15 - 25 ˂ 15

E. GUIDELINES FOR CLASSIFICATION OF DISCONTINUITY conditions

Discontinuity length (persistence)

Rating

˂ 1 m

6

1 – 3 m

4

3 – 10 m

2

10 – 20 m

1

˃ 20 m

0

Separation (aperture)

Rating

None

6

˂ 0.1 mm

5

0.1 – 1.0

mm

4

1 – 5 mm

1

˃ 5 mm

0

Roughness

Rating

Very rough

6

Rough

5

Slightly rough

3

Smooth

1

Slickensided

0

Infilling (gouge) Rating

None

6

Hard filling ˂ 5 mm

4

Hard filling ˃ 5

mm 2

Soft filling ˂ 5

mm 2

Soft filling ˃ 5 mm

0

Weathering

Rating

Unweathered

6

Slightly weathered

5

Moderately weathered

3

Highly weathered

1

Decomposed

0




F. EFFECT OF DISCONTINUITY AND DIP ORIENTATON IN TUNNELLING

Strike perpendicular to tunnel axis Strike parallel to tunnel axis

Drive with dip – Dip 45 - 90° Drive with dip – Dip 20 - 45° Dip 45 - 90° Dip 20 - 45°

Very favourable Favourable Very unfavourable Fair

Drive against dip – Dip 45 - 90° Drive against dip – Dip 20 - 45° Dip 0 - 20° – irrespective of strike

Fair Unfavourable Fair

Table A-2: Classification of individual parameters used in the Tunneling Quality Index Q (Barton,

2002)

NOTES VALUE DESCRIPTION

(i) Where RQD is reported or measured as≤ 10 (including 0), a nominal value of 10 is used to evaluate Q. (ii) RQD intervals of 5, i.e., 100, 95, 90 etc. are sufficiently accurate.

Rating of RQD 0 – 25 25 – 50 50 – 75 75 – 90 90 – 100

1. ROCK QUALITY DESIGNATION A. Very poor B. Poor C. Fair D. Good E. Excellent

(i) For intersections use (3.0×Jn). (ii) For portals use (2.0×Jn)

Rating of Jn 0.5 – 1.0 2 3 4 6 9 12 15

20

2. JOINT SET NUMBER A. Massive, no or few joints B. One joint set C. One joint set plus random D. Two joint sets E. Two joint sets plus random F. Three joint set G. Three joint sets plus random H. Four or more joint sets, random, heavily jointed, "suger cube", etc. I. Crushed rock, earthlike

(i) Descriptions refer to small-scale features and intermediate scale features, in that order. (ii) Add 1.0 if the mean spacing of the relevant joint set is greater than 3 m. (iii) Jr = 0.5 can be used for planar, slickensided joints having lineation, provided the lineations are favorably oriented. (iv) Jr and Ja classification is applied to the joint set or discontinuity that is least favorable for stability both from the point of view of

orientation and shear resistance,

Rating of Jr

4 3 2.0 1.5 1.5 1.0 0.5

1.0 1.0

3. JOINT ROUGHNESS

NUMBER (a) rock- wall contact and

(b) Rock- wall contact before 10

cm shear

A. Discontinuous joint B. Rough or irregular, undulating C. Smooth, undulating D. Slickensided, undulating E. Rough or irregular, planar F. Smooth, planar G. Slickensided, planar (c) No rock- wall contact when

sheared H. Zone containing clay minerals thick enough to prevent rock wall contact I. Sandy, gravelly or crushed zone thick enough to prevent rock wall contact




Rating of Ja

0.75 1.0 2.0 3.0 4.0 4.0 6.0 8.0 8 – 12 6,8 or 8 – 12 5 10,13 or 13 – 20

approx. ør

(degree) – 25 – 35 25 – 30 20 – 25 8 – 16 25 – 30 16 – 24 12 – 16 6 – 12 6 – 24 – 6 – 24

4. JOINT ALTERATION NUMBER (a) Rock-wall contact (No mineral filling, only coating) A. Tightly healed, hard, non-softening, impermeable filling, i.e., quartz or epidote B. unaltered joint walls, surface staining only C. Slightly altered joint walls. Non-softening mineral coatings, sandy particles, clay- free disintegrated rock, etc. D. Silty or sandy clay coatings, small clay fraction (non-softening) E. Softening or low friction clay mineral coatings, i.e., kaolinite, mica. Also chlorite, talc, gypsem and graphite, etc. and small quantities of swelling clays (Discontinuous coatings, 1 – 2 mm or less in thickness (b) Rock-wall contact before 10 cm shear (Thin mineral

fillings)

F. Sandy particles, clay-free disintegrated rock, etc. G. Strongly over-consolidated, non-softening clay mineral fillings (continuous, < 5 mm in thickness) H. Medium or low over-consolidation, softening, clay mineral fillings (continuous, < 5 mm in thickness) J. Swelling clay fillings, i.e., montmorillonite (continuous, < 5 mm in thickness). Value of Ja depends on percent of swelling clay-size particles, and access to water, etc. (c) No rock-wall contact when sheared (Thick mineral

fillings) K, L, M. Zones or bands of disintegrated or crushed rock and clay (see G, H, J for description of clay condition) N. Zones or bands of silty or sandy clay, small clay fraction (non-softening) O, P, R. Thick, continuous zones or bands of clay (see G, H, J for description of clay condition)

Table A-2: (cont′d) Classification of individual parameters used in the Tunneling Quality Index Q

(Barton, 2002) Notes:

(i) Factors C to F are crude estimates. Increase Jw if

drainage measures are installed.

(ii) Special problems caused by ice formation are not

considered.

(iii) For general characterization of rock masses distant

from excavation influences, the use of Jw = 1.0, 0.66, 0.5,

0.33, etc. as depth increases from 1 – 5, 5 – 25, 25 – 250 to

> 250 m is recommended, assuming that RQD/Jn is low

enough (e.g., 0.5 – 25) for good hydraulic conductivity.

This will help to adjust Q for some of the effective stress

and water softening effects, in combination with appropriate

characterizat ion values of SRF. Correlat ions with depth-

dependent static modulus of deformation and seismic

velocity will then fo llow the practice used when these where

developed.

Rating of Jw

1

0.66

0.5

0.33

0.2 –

0.1

Approx. water

pressure

(MPa)

< 0.1

0.1 – 0.25

0.25 – 1.0

0.25 – 1.0

> 1.0

5. JOINT WATER

REDUCTION

A. Dry excavations or

minor inflow, i.e., 5

liter/min locally

B. Medium inflow or

pressure, occasional out-

wash of joint filling

C. Large inflow or high

pressure in competent

rock with unfilled joints

D. Large inflow or high

pressure, considerable

out-wash of joint fillings

E. Exceptionally h igh

inflow or water pressure

at blasting, decaying with

time




0.1 –

0.05

> 1.0 F. exceptionally high inflow

or water pressure

continuing without

noticeable decay

Notes:

(i) Few case records available where depth of crown below

surface is less than span width, suggest SRF increase from

2.5 to 5 for such cases (see H).

(ii) Cases L, M and N are usually most relevant for support

design of deep tunnel excavation in hard massive rock

masses, with RQD/Jn ratios from about 50 – 100.

(iii) For general characterization of rock masses distant

from excavation influences, the use of SRF = 5, 2.5, 1.0 and

0.5 is recommended as depth increases from 0 – 5, 5 – 25,

25 – 250, > 250 m. This will help to adjust Q for some of

the effective stress effects, in combination with appropriate

characterizat ion values of Jw. Correlations with depth-

dependent static modulus of deformation and seismic

velocity will then follow the practice used when these were

developed.

Rating of SRF

10.0

5.0

2.5

7.5

5.0

2.5

5.0

2.5

1.0

0.5 –

2.0

5 – 50

50 –

100

200 –

400

5 – 10

10 – 20

6. STRESS REDUCTION FACTOR (a) Weakness zones intersecting

excavation, which may cause loosening of

rock mass when tunnel is excavated

A. Multiple occurrence of weakness zones

containing clay or chemically

disintegrated rock, very loose surrounding rock

(any depth)

B. Single-weakness zones containing clay or

chemically disintegrated rock (depth of

excavation ≤ 50 m)

C. Single-weakness zones containing clay or

chemically disintegrated rock (depth of

excavation > 50 m)

D. Multip le-shear zones in competent rock

(clay-free), loose surrounding rock (any depth)

E. Single-shear zones in competent rock (clay-

free)(depth of excavation ≤50m)

F. Single-shear zones in competent rock (clay-

free)(depth of excavation > 50 m)

G. Loose, open joints, heavy jointed or "sugar

cube", etc. (any depth)

σө/σc

< 0.01

0.01 –

0.3

0.3 –

0.4

0.5 –

0.65

0.65 –

1.0

> 1

1 – 5

> 5

σc/σ1

> 200

200 –

10

10 – 5

5 – 3

3 – 2

< 2

-

-

(b ) Competent rock,

rock stress problems

H. Low stress, near surface

open joints

J. Medium stress, favorable

stress condition

K. High stress, very tight

structure (usually

favorable to stability, may

be unfavorable to

wall stability)

L. Moderate slabbing after

> 1 hour in massive rock

M. Slabbing and rock burst

after a few minutes in

massive rock

N. Heavy rock burst (strain-

burst) and immediate

deformation in massive

rock

(c) Squeezing rock;

plastic flow of incompetent

rock under the influence of

high rock

pressures

O. Mild squeezing rock

pressure

P. Heavy squeezing rock

pressure




5 – 10

10 – 15

-

-

-

-

(d) Swelling rock;

chemical swelling activity

depending on presence of

water

Q. Mild swelling rock

pressure

R. Heavy swelling rock

pressure

guidlines on the excavation process & support measures of

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