Guidlines On The Excavation Process & Support

Inte rnational Journal of Engineering Technology, Manage ment and Applied Sciences

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

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).

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



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

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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



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

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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

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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).



www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476 Table 1: Major rock mass classification systems (summarized from Edelbro, 2004; Palmstrom, 1995) Name Classification

of

Author and First version

Country of origin

Applications

Rock Load Theory

Terzaghi, 1946

USA

Tunnels with steel supports

Stand-up time

Lauffer, 1958

Austria

Tunneling

The New Austrian Tunneling Method(NATM)

Rabcewicz, 1964/65 and 1975

Austria

Tunneling in incompetent (overstressed) ground

Form and Type *) Description F Behavior F, Function T Description F General T Descriptive F Behaviouristic F, Tunneling concept

Rock mass (RM R-system)

Bieniawaski, 1974

South Africa

Tunnels, mines, foundations etc.

Nu merical F, Functional T

Tunnels, large chambers For use in communicat ion

Nu merical F, Functional T Descriptive F, General T Descriptive F, General T Nu merical F, Functional T Nu merical F, Functional T

rating

Tunnelling quality index (Q-system) The typological classification Basic geotechnical description (BGD) Rock mass strength (RM S) Geological St rength Index (GSI)

Barton et al., 1974 Matula and Holzer, 1978

Rock (N)

Goel et 1995

mass

Number

ISRM, 1981 Stille et al., 1982 Hoek et al., 1995 al.,

Norway

-

For general use

Sweden India

Mines, tunnels

Nu merical F, Functional T

Remarks Unsuitable for modern tunneling Conservati ve Utilized in squeezing ground conditions Unpublish ed base case records

Modified RM R

Stressfree Qsystem

Rock engineering, Nu merical F, Norway communicat ion, Functional T characterizat ion *)Definit ion of the following expressions (Palmstrom, 1995) Descriptive F = Descriptive Form: the input to the system is mainly based on descriptions. Nu merical F = Nu merical 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 examp le for rock support) Rock (RM i)

mass

index

Arild Palmstro m, 1995

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.



www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476 Applying this classification system, the rock mass is divided into a number of struc tural 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 RMRsystem 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 bl asting, (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)



www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476 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) Rock bolts (20 mm Rock mass Excavation diameter, fully Shotcrete Steel sets class grouted) I -Very good Full face, 3 m rock Generally no support required except spot bolting advance. RMR: 81 – 100 Full face, 1 – 1.5 m Locally both in crown 50 mm in II- Good rock advance. Complete 3 m long spaced 2.5 m crown where None. RMR: 61 – 80 support 20 m from with occasional wire required. face. mesh. Top heading and bench 1.5 – 3 m Systematic bolts 4 m advance in top 50 – 100 mm long spaced 1.5 – 2 m III- Fair rock heading. Commence in crown and in crown and walls None. RMR:41 – 60 support after each 3o mm in with wire mesh in blast. sides. crown. Complete support 10 m from face. Top heading and bench 1.0 – 1.5 m Light to advance in top Systematic bolts 4 – 5 100 – 150 mm medium ribs IV- Poor rock heading. m long, spaced 1 – 1.5 in crown and spaced 1.5 m RMR: 21 – 40 Install support m in crown and walls 100 mm in where concurrently with with wire mesh. sides. required. excavation, 10 m from face. Medium to Multiple drifts 0.5 – heavy ribs 1.5 m advance in top Systematic bolts 5-6 150-200mm in spaced 0.75 m V-Very poor heading. Install m long, spaced 1-1.5 crown and 150 with steel rock support concurrently m in crown and walls mm in sides, lagging and RMR: < 20 with excavation. with wire mesh. Bolt and 50 mm on forepoling if Shotcrete as soon as invert. face. required. Close possible after blasting. invert. 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).



www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476 Table 4: Classification of rock mass based on Q-values (Barton, et al., 1974) Rock Quality Class Q- value Exceptionally good 400 – 1000 A Extremely good 100 – 400 Very good 40 – 100 B Good 10 – 40 C Fair 4 – 10 D Poor 1–4 E Very poor 0.1 – 1 F Extremely poor 0.01 – 0.1 G Exceptionally poor 0.001 – 0.1

RQD Jr Jw , where the parameters are:   Jn Ja SRF 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 A2) the rating of the parameters is clarified. The Q value is expressed as following: Q 

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: De 

Excavation span, diameter or height (m) The excavation support ratio (ESR) reflects the Excavation Support Ratio (ESR)

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.



www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476 Table 5: The various values of ESR according to NGI (1997) Type of Excavation ESR A Temporary mine openings, etc. 3–5 B Vertical shafts: i)circular sections 2.5 ii) rectangular/square section 2.0 C Permanent mine openings, water tunnels for hydro power (exclude 1.6 high pressure penstocks), pilot tunnels, drifts and headings for large openings D Storage rooms, water treatment plants, minor road and railway 1.3 tunnels, surge chambers, access tunnels, etc. E Power stations, major road and railway tunnels civil defense 1.0 chambers, portals, intersections, etc. F Underground nuclear power stations, railway stations, sports and 0.8 public facilitates, factories, etc. G Very important caverns and tunnels with a long lifetime, tunnels for 0.5 gas pipe lines. 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 wa s updated by (Grimstad & Barton, 1993). Figure (7) shows this updated chart.

Figure 7: Esti mated support categories based on the tunneling quality index Q (Gri mstad & B arton, 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



www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476 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 RMU17). Table 6: Rock mass classification of the rock mass units along the proposed Haibat Sultan Tunnel according to the RMR-system RMUNo.

Formation

1(inlet) 2(inlet) 3 4 5 6 7 8

Fatha Fatha Fatha Pilaspi Pilaspi Pilaspi Pilaspi Pilaspi

Thickness along the tunnel axis (m) 53 7 25 7 18 7 15 30

9

Pilaspi

10

Ratings UCS 4 7 12 12 15 12 15 12

RQD Rating 8 8 17 20 17 17 20 20

S pacing of discontinuities 8 9 13 12 12 12 12 12

Groundwater condition 15 15 7 7 7 7 7 7

Discontinuity condition* 23 10 24 25 25 26 23 26

Orientation of discontinuities 0 -2 0 0 -2 0 -2 -2

RMRvalue 58 47 73 76 74 74 76 75

40

12

3

5

7

2

-12

17

Pilaspi

7

7

3

5

7

4

-12

14

11

Pilaspi

18

12

13

9

7

22

0

63

12

Gercus

100

2

3

5

7

2

-12

7

13

Gercus

10

4

13

9

7

23

0

56

14

Gercus

40

4

3

5

7

2

-12

9

15

Kolosh

100

7

3

5

7

2

-12

12

16

Kolosh

63

7

3

5

7

2

-12

12

17

Khurmala

30

12

20

12

7

26

-2

75

18

Kolosh

300

7

3

9

7

2

-12

16

19 (outlet)

Kolosh

30

1

3

8

7

2

-12

9

* 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 Thickness along the Ratings Rock RMUFormation tunnel QMass No. RQD Jn Jr Ja Jw SRF axis (m) value Quality 2.5 – 1(inlet) Fatha 53 32 2×(15) 2 1 1.00 1.22 Poor 1 2.5 – 2(inlet) Fatha 7 44 2×(15) 3 2 1.00 1.26 Poor 1 2.5 – 3 Fatha 25 84 15 3 1 0.5 4.8 Fair 1 2.5 – 4 Pilaspi 7 96 9 2 1 0.5 6.09 Fair 1 2.5 – 5 Pilaspi 18 73 15 3 1 0.5 4.17 Fair 1 6 Pilaspi 7 74 15 3 1 0.5 2.5 – 4.22 Fair


Rock Mass Quality Fair Fair Good Good Good Good Good Good Very poor Very poor Good Very poor Fair Very poor Very poor Very poor Good Very poor Very poor


www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476 1 2.5 – 5.25 1 2.5 – 8.66 1

7

Pilaspi

15

92

15

3

1

0.5

8

Pilaspi

30

91

9

3

1

0.5

9

Pilaspi

40

10

20

1

10 0.5

10

0.0025

10

Pilaspi

7

10

20

2

10 0.5

7.5

0.006

11

Pilaspi

18

66

9

2

1

2.5 – 4.19 1

Fair

12

Gercus

100

10

20

1

15 0.5

10

Except. poor

13

Gercus

10

61

9

3

1

0.5 – 8.13 2

14

Gercus

40

10

20

1

16 0.5

10

0.0015

15

Kolosh

100

10

20

1

16 0.5

10

0.0015

16

Kolosh

63

10

20

1

10 0.5

10

0.0025

17

Khurmala

30

92

9

3

1

2.5 – 8.75 1

18

Kolosh

300

10

20

1

10 0.5

19 (out let)

Kolosh

30

10

2×(20)

1

16 0.66 10

0.5

0.5

0.5

10

0.0016

0.0025 0.001

Fair Fair Except. poor Except. poor

Fair Except. poor Except. poor Except. poor Fair Except. poor Except. poor

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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.

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CONCLUSIONS The following conclusions have been reached as an outcome of this study: 1Since 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. 2Generally, 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. 3The 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. 4Because 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



www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476 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. 5According 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. 6According 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. 7It 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.

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RECOMMENDATIONS Based on the outcomes of this study, the following recommendations have been suggested: 1Great 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. 2Because 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. 3The 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). 4It 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.



www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476 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 Rock mass quality; RMR-value range/ RMU-No. Q-value range

Guide for Support recommendations excavation method (RMR) RMR 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.

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

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.

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

Locally, Fully grouted (20 mm diameter) systematic rock Full face, 1 – 1.5 bolts in crown 3m long, m advance, spaced 2.5 m with occasional complete support wire mesh. Shotcrete 50 mm 20 m from face. in crown where required.

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

Multiple drifts 0.5 RMU-9, – 1.5 m advance RMU-10, in top heading, Very poor to RMU-12, install support exceptionally poor; RMU-14, concurrently with RMR(< 20)/ Q (0.001 RMU-15, excavation, – 0.01) RMU-16, shotcrete as soon RMU-18 and as possible after RMU-19 blasting.

Poor to fair; RMU-1& RMR (41 – 60)/ Q (1 RMU-2 – 4)

RMU-3, RMU-4, RMU-5, Fair to good; RMU-6, RMR (61 – 80)/ Q (4 RMU-7, – 10) RMU-8, RMU-11, RMU-13 and RMU-17

Q-system

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



www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476 7-

REFERENCES 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. nd [4] Bell, F. G., 2007: Engineering geology (2 ed.), Elsevier, Amsterdam, 581 p. [5] Bieniawski, Z. T., 1989: Engineering rock mass classifications, Wiley, New York, 251 p. rd [6] Brady, B. H. G. and Brown, E. T., 2005: Rock mechanics for underground mining (3 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. [1]

8-

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



www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476 Table A-1 : Details of Rock Mass Rating System (After Bieniawski, 1989) A. CLASS IFICATION PARAMETERS AND THEIR RATINGS Parameter Rating of values

1

2 3

4

Strength of intact rock material

˃ 10 M Pa

4 – 10 MPa

2 – 4 MPa

1 – 2 MPa

Uniaxial comp. strength

> 250 M Pa

100 – 250 MPa

50 – 100 MPa

25 – 50 MPa

15 90 % - 100 % 20 ˃2m 20 Very rough surfaces Non continuous No separation Unweathered wall rock 30

12 75 % - 90 % 17 0.6 – 2 m 15

7 50 % -75 % 13 200 – 600 mm 10

Slightly rough surfaces Separation ˂1mm Slightly weathered walls

Slightly rough surfaces Separation ˂ 1mm Highly weathered walls

25

20

4 25 % - 50 % 8 60 – 200 mm 8 Slickensided surfaces or Gouge ˂ 5 mm thick or separation 1-5 mm Continuous 10

Non

˂ 10

10 - 25

25 - 125

˃ 125

0

˂ 0.1

0.1 – 0.2

0.2 – 0.5

˃ 0.5

Dripping 4

Flowing 0

Rating Drill Core Quality RQD Rating Spacing of discontinuities Rating

Condition (See E)

of

discontinuities

Rating

5

Ground water

Inflow per 10 m tunnel length (l/m) (Joint water press)/(M ajor principal σ) General conditions

Completely dry Damp Wet Rating 15 10 7 B. RATING ADJUS TMET FOR D IS CONTINUITY ORIENTATIONS (See E) Strike and dip orientations Very favourable Favourable Fair Tunnels & mines 0 -2 -5 Ratings Foundations 0 -2 -7 Slopes 0 -5 -25 C. ROCK MASS CLASS ES DETERMINED FROM TOTAL RATINGS Rating 100  81 80  61 60  41 Class number I II III Descriptions Very good rock Good rock Fair rock D. MEANING OF ROCK CLASS ES Class number I II III 20 yrs for 15 m 1 year for 10 m 1 week for 5 m Average stand-up time span span span Cohesion of rock mass (kPa) ˃ 400 300 - 400 200 - 300 Friction angle of rock mass (deg) ˃ 45 35 - 45 25 - 35 E. GUIDELIN ES FOR CLASS IFICATION OF DIS CONTINUITY con ditions Discontinuity length (persistence) ˂1m 1–3m 3 – 10 m Rating 6 4 2 0.1 – 1.0 Separation (aperture) None ˂ 0.1 mm mm Rating 6 5 4 Roughness Very rough Rough Slightly rough Rating 6 5 3 Hard filling ˃ 5 None Hard filling ˂ 5 Infilling (gouge) mm mm Rating 2 6 4 Weathering Rating

For this low range uniaxial compressive test is preferred 1 – 5 - 25 ˂ 1 5 MPa MPa MPa 2 1 0 ˂ 25 % 3 ˂ 60 mm 5

Point-load strength index

Unweathered 6

Slightly weathered 5

M oderately weathered 3

Soft gouge ˃ 5 mm thick or Separation ˃ 5 mm Continuous 0

Unfavourable -10 -15 -50

Very unfavourable -12 -25

40  21 IV Poor rock

˂ 21 V Very poor rock

IV 10 hrs for 2.5 m span 100 - 200 15 - 25

V

10 – 20 m 1

˃ 20 m 0

1 1

– 5 mm

30 min. for 1 m span ˂ 100 ˂ 15

˃ 5 mm 0

Smooth 1 Soft filling ˂ 5 mm 2

Slickensided 0 Soft filling ˃ 5 mm

Highly weathered 1

Decomposed 0


0


www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476 F. EFFECT OF DIS CONTINUITY AND DIP ORIENTATON IN TUNN ELLING 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) DESCRIPTION VALUE NOTES 1. ROCK QUALITY Rating of RQD (i) Where RQD is reported or measured as≤ 10 (including 0), a nominal value of 10 is used to DESIGNATION A. Very poor 0 – 25 evaluate Q. B. Poor 25 – 50 C. Fair 50 – 75 (ii) RQD intervals of 5, i.e., 100, 95, 90 etc. are D. Good 75 – 90 sufficiently accurate. E. Excellent 90 – 100 (i) For intersections use (3.0×Jn). 2. JOINT SET NUMBER Rating of Jn A. Massive, no or few joints 0.5 – 1.0 B. One joint set 2 (ii) For portals use (2.0×Jn) C. One joint set plus random 3 D. Two joint sets 4 E. Two joint sets plus random 6 F. Three joint set 9 G. Three joint sets plus random 12 H. Four or more joint sets, random, 15 heavily jointed, "suger cube", etc. 20 I. Crushed rock, earthlike (i) Descriptions refer to small-scale features and 3. JOINT ROUGHNESS Rating of Jr intermediate scale features, in that order. NUMBER (a) rock- wall contact and (b) Rock- wall contact before 10 (ii) Add 1.0 if the mean spacing of the relevant cm shear joint set is greater than 3 m. A. Discontinuous joint 4 B. Rough or irregular, undulating 3 (iii) Jr = 0.5 can be used for planar, slickensided C. Smooth, undulating 2.0 joints having lineation, provided the lineations D. Slickensided, undulating 1.5 are favorably oriented. E. Rough or irregular, planar 1.5 F. Smooth, planar 1.0 (iv) Jr and Ja classification is applied to the joint G. Slickensided, planar 0.5 set or discontinuity that is least favorable for (c) No rock- wall contact when stability both from the point of view of sheared orientation and shear resistance, H. Zone containing clay minerals thick enough 1.0 to prevent rock wall contact I. Sandy, gravelly or crushed zone 1.0 thick enough to prevent rock wall contact



www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476 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, clayfree 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 (nonsoftening) O, P, R. Thick, continuous zones or bands of clay (see G, H, J for description of clay condition)

approx. (degree)

ør Rating of Ja

– 25 – 35 25 – 30

0.75 1.0 2.0

20 – 25 8 – 16

3.0 4.0

25 – 30 16 – 24

4.0 6.0

12 – 16

8.0

6 – 12

8 – 12

6 – 24

6,8 or 8 – 12 5 10,13 or 13 – 20

– 6 – 24

Table A-2: (cont′d) Classification of individual parameters used in the Tunneling Quality Index Q (Barton, 2002) 5. JOINT REDUCTION

WATER

A. Dry excavations or minor inflow, i.e., 5 liter/ min locally B. Med iu m inflo w or pressure, occasional outwash of joint filling C. Large inflo w 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

Approx. water pressure (MPa)

Rating of Jw

< 0.1

1

0.1 – 0.25

0.66

0.25 – 1.0

0.5

0.25 – 1.0

0.33

> 1.0

0.2 0.1

–

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 fro m 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 co mb ination with appropriate characterizat ion values of SRF. Correlat ions with depthdependent static modulus of deformation and seismic velocity will then fo llo w the practice used when these where developed.



www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476 F. exceptionally high inflow > 1.0 or water pressure continuing without noticeable decay 6. STRESS REDUCTION FACTOR (a) Weakness zo nes 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 (clayfree)(depth of excavation ≤50m) F. Single -shear zones in competent rock (clayfree)(depth of excavation > 50 m) G. Loose, open joints, heavy jointed or "sugar cube", etc. (any depth) (b ) Competent rock, σc/σ1 σө/σc rock stress problems H. Low stress, near surface > 200 < 0.01 open joints J. Medium stress, favorable 200 – 0.01 – stress condition 10 0.3 K. High stress, very tight 10 – 5 0.3 – structure (usually 0.4 favorable to stability, may be unfavorable to wall stability) L. Moderate slabbing after 5 – 3 0.5 – > 1 hour in massive rock 0.65 M. Slabbing and rock burst 3 – 2 0.65 – after a few minutes in 1.0 massive rock N. Heavy rock burst (strain- < 2 >1 burst) and immediate deformation in massive rock (c) Squeezing rock; plastic flow of incompetent rock under the influence of high rock pressures O. M ild squeezing rock 1– 5 pressure P. Heavy squeezing rock >5 pressure

0.1 0.05

–

Rating of SRF

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).

10.0 (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 fro m about 50 – 100. 5.0 (iii) For general characterization of rock masses distant fro m excavation influences, the use of SRF = 5, 2.5, 1.0 and 0.5 is reco mmended 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 co mbination with appropriate characterizat ion values of Jw. Correlations with depthdependent static modulus of deformation and seismic velocity will then follo w the practice used when these were developed.

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



www.ijetmas.com August 2015, Volume 3, Issue 8, ISSN 2349-4476 (d) Swelling rock; chemical swelling activity depending on presence of water Q. Mild swelling rock pressure R. Heavy swelling rock pressure

-

-

5 – 10

-

-

10 – 15
