Rock Slope Stability and Excavatability

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Engineering Geology 96 (2008) 17 – 27 www.elsevier.com/locate/enggeo

Rock slope stability and excavatability assessment of rocks at the Kapikaya dam site, Turkey Zulfu Gurocak a, ⁎, Selcuk Alemdag a , Musharraf M. Zaman b a

b

Department of Geology, Firat University, Elazig, 23119, Turkey College of Engineering, University of Oklahoma, 202 West Boyd Street, Room 334, Norman, OK 73019-1024, USA

Received 5 January 2007; received in revised form 27 July 2007; accepted 17 August 2007 Available online 4 September 2007

Abstract

This paper presents the slope stability and excavatability assessment of rocks at the Kapikaya dam site that contains diabases. Both field and laboratory studies were carried out. The field study involved detailed discontinuity surveys. Laboratory tests were carried out to determine uniaxial compressive strength, Young's modulus, unit weight, point load strength index and shear strength parameters of discontinuities. Kinematical and numerical analyses were performed to determine right and left slopes at the dam site. According to kinematical analyses, the types of planar and wedge failure are not expected at the site. Also, shear strength reduction analyses was carried out using Phase2 for the right and left slopes at the dam site. According to results of numerical analysis, Strength Reduction Factor (SRF) of the right and left slopes are 8.08 and 6.5 respectively and any rotational failure will not occur. The excavation category of the diabases was determined as easy ripping for the right slope and easy-hard ripping for the left slope. © 2007 Elsevier B.V. All rights reserved. Keywords: Excavatability; Kapikaya dam; Kinematical analysis; Rock slope stability; Shear strength reduction analyses

1. Introduction

The slope stability and excavatability of rocks is an import imp ortant ant pro problem blem in geo geotech technica nicall engi engineer neering. ing. Thi Thiss holds ho lds fo forr bot both h the de desi sign gn an and d con constr struct uction ion st stage ages. s. Currently, a number of methods are being used for the assessment of slope stability and excavatability (Hoek (Hoek and Bray, 1981; Goodman, 1989; Pettifer and Fookes,

⁎

Corresponding author. Tel.: +90 424 237 0000/5991; fax: +90 424 241 1226. E-mail addr addresses: esses: [email protected] , [email protected] (Z. Gurocak). 0013-7952/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.enggeo.2007.08.005 doi: 10.1016/j.enggeo.2007.08.005

1994). Kine 1994). Kinemat matical ical,, lim limit it equi equilibr librium ium and num numeric erical al analyses are generally preferred for the evaluation of rock. Kinematical analysis refers to the motion of bodies without reference to the forces that cause them to move. Equilibrium analyses consider the shear strength along the failure surface, the effects of pore water pressure and the inf influen luence ce of ext externa ernall for forces ces suc such h as rei reinfo nforcin rcing g elements or seismic accelerations. On the other hand, numerical analyses such as finite element and distinct eleme el ement nt me metho thods ds ar aree pe perfo rform rmed ed to co confi nfirm rm re resu sults lts occurred from kinematical and equilibrium analysis. A number of methods have been suggested by researchers (Kir Kirste sten, n, 1982 1982;; Mint Minty y and Kear Kearns, ns, 1983 1983;; Cate Caterpi rpillar llar,, 1988; Hadjigeorgiou and Scoble, 1990; Karpuz et al.,

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Z. Gurocak et al. / Engineering Geology 96 (2008) 17 – 27

1990; MacGregor et al., 1994; Pettifer and Fookes, 1994) to examine the excavatability of rocks. Each of these methods considers a different set of geotechnical parameters such as seismic velocity, point load strength index, weathering, discontinuity spacing and groundwater. The field site used in this study is located about 30 km east of Malatya, Turkey (Fig. 1). The Kapikaya dam, which is under construction on the Mamikan stream, is located at this site. The dam project is designed to regulate drainage and irrigate agricultural lands belonging to the Kale plain. The design of the Kapikaya dam project is under the supervision of the General Directorate of State Hydraulic Works (1991), the Ministry of Energy and Natural Resources in Turkey. The dam site is located within the Ispendere Ophiolites, which is composed of diabases. Geological mapping and geotechnical descriptions were conducted in the field. The physical, mechanical and elastic properties of the rocks under consideration were determined from laboratory testing on intact rock samples. These tests include an evaluation of uniaxial compressive strength (σc), Young's modulus ( E ), Poisson's ratio (v ), point load strength index (Is(50)) and unit weight (γ). The main orientation, spacing, persistence, aperture, filling, weathering and roughness of discontinuities were described using the scan-line survey method following the ISRM (1981) description criteria. Kinematical and finite

element method analyses were performed for right and left slopes at the dam site. The method suggested by Pettifer and Fookes (1994) was used for the assessment of rock excavatability. 2. Geology, field and laboratory studies

The study area is located approximately 30 km east of Malatya in eastern Turkey (Fig. 1) where the Kapikaya dam site is under construction on the Mamikan stream. Units of various ages from the Upper Jurassic to the Quaternary are exposed in the region. Upper Jurassic– Lower Cretaceous ophiolitic rocks are exposed at the Kapikaya dam site (Yazgan, 1984). These rocks are part of the extensive Jurassic–Cretaceous aged ophiolitic complex in the Southeast Anatolian Thrust Zone. These ophiolitic rocks are found as allochthonous bodies in the Eastern Taurus. The ophiolitic rocks which consist of diabases in the study area are a part of Ispendere Ophiolites. Also, these rocks are called sheeted dyke complex. The diabases are yellowish-grey color and well jointed. Although the diabases are moderately weathered on the upper levels, they are slightly weathered on the lower levels at the dam site. These rocks are cut by single diabase dykes having a dark grey color and a thickness of 20–75 cm. Diabases are primarily composed of fine grained plagioclase and clinopyroxene crystals. Some

Fig. 1. The location map of the study area.


carbonatization of plagioclases and cloritization of clinopyroxcene can be detected at the site. Overlying the mainly Upper Jurassic–Lower Cretaceous deposits are talus and alluvial materials. Talus displays a wide distribution in the study area (Fig. 2). Talus is originated from diabases blocks with clayey matrix and is observed on both the right and the left banks of the dam site. From the drillings conducted by the General Directorate of State Hydraulic Works (DSI, 1991) at the dam site, the thicknesses of talus deposits were found to vary between 0.5 m and 8 m. The alluvium is observed in the Mamikan stream bed (Fig. 2) and originated from different rocks around the study area. These deposits consist of gravel, sand and

19

silt. From the drillings conducted by the General Directorate of State Hydraulic Works (DSI, 1991) at the dam site, the thicknesses of alluvium deposits were found to vary between 1 and 6 m. During the field surveys, engineering geological map of the Kapikaya dam site was constituted. The field studies also included measurements of orientation, persistence, spacing, aperture, and roughness, degree of weathering and filling of discontinuities in the diabases. In addition, an examination was made of the 722 m of core from 16 boreholes drilled to determinate engineering geological properties on vertical and horizontal directions of rocks such as RQD, permeability and weathering by the General Directorate of State Hydraulic Works (DSI, 1991).

Fig. 2. The geological map of the study area.

20


Table 1 The percentage distribution of RQD values of diabases RQD

Rock quality

Distribution %

0–25 25–50 50–75 75–90 90–100

Very poor Poor Fair Good Excellent

3 10 30 40 17

The locations of the boreholes were plotted on the geological map of the dam site (Fig. 2). The RQD values of the diabases were determined using borehole cores. According to RQD divisions proposed by Deere (1964), the diabases of the rocks have the following distribution: 17% excellent, 40% good, 30% fair, 10% poor, and 3% very poor (Table 1). Due to the joint spacing values increase at deeper levels, the RQD values of diabases increase at the deeper levels. Furthermore, these joints are not filled by filling material such as clay, calcite at the deeper levels contrary to the upper levels. Engineering geological properties of the rocks ex posed in the study area were determined on the basis of field observations/measurements and laboratory tests. The description of rock material and mass characteristics were based on the ISRM methods (ISRM, 1981). A total of 67 core samples and 18 oriented block sam ples were collected from the field for laboratory testing. Uniaxial compressive strength (σc), modulus of elasticity intact rocks ( E ), Poisson's ratio (v ), point load strength index (Is(50)), unit weight (γ) and shear strength parameters of the joints by direct shear tests were determined in accordance with the ISRM methods (ISRM, 1981, 1985). As the study area is located in a seismically active region, the diabases exposed around the Kapikaya dam

site contain systematic joint sets. Table 2 shows the main orientation, spacing, persistence, aperture and roughness of discontinuities. These were described using the scanline survey method following the ISRM (1981) description criteria. The degree of weathering of the discontinuous surfaces was assessed using the Schmidt hammer, and the weathering index was calculated from the following equation by Singh and Gahrooee (1989): W c ¼

rc

ð1Þ

JCS

where Uniaxial compressive strength of fresh rock (MPa), and Strength of discontinuity surface (MPa).

σc

JCS

The strength of discontinuity surface (JCS) was calculated from the following equation by Miller (1965): Log JCS ¼ 0:00088g R þ 1:01

ð2Þ

where Bulk volume weight (kN/m3), and Hardness value from rebounding of the Schmidt hammer.

γ R

In the study area, a total of 846 joint measurements were taken from diabases. Discontinuity orientations were processed utilizing a commercially available software DIPS 5.0 (Rocscience, 1999), based on equalangle stereographic projection, and major joint sets were

Table 2 Material of diabases and joints properties Property

Number of tests

Uniaxial compressive strength (σc, MPa) Young's modulus of intact rock ( E , GPa) Poisson's ratio Point load strength index (Is(50), MPa) Unit weight (γ, kN/m3) RQD (%) Joint set number Spacing of discontinuities (mm) Persistence of discontinuities (m) Aperture of discontinuities (mm) Roughness of discontinuities Infilling Weathering degree Groundwater conditions

62 28 28 54 62

Mean

Max

Min

Std. dev.

93.85 286.90 38.74 35.43 25.63 87.38 7.64 18.66 0.261 0.283 0.238 0.0234 5.37 9.71 0.71 1.981 29.08 31.66 27.71 1.552 66 100 7 21.14 Three joint sets plus random 18–197 (average 120) Generally 1–3 m, however occasionally b 1 m and 10–20 m Generally N 5 mm, however occasionally 0.1–0.5 mm Generally rough, however occasionally smooth Generally calcite having a thickness of N 5 mm, however occasionally b 5 mm calcite Generally slightly weathered, occasionally moderately weathered Generally dry occasionally damp


21

Fig. 3. Stereographic projection of joint sets in diabases.

distinguished for diabases (Fig. 3). The major orientations of the joint sets for diabases are listed below: Joint set 1: 68/75 Joint set 2: 78/185 Joint set 3: 85/143 According to the ISRM (1981), the joint sets in the diabases have close to very close spacing, low persistence and rough-planar. While these joint sets are open and moderately weathered character at the surface, they are tight and slightly weathered character at deeper levels. Uniaxial compressive strength (σc), modulus of elasticity of intact rock ( E ), Poisson's ratio (v ), point load strength index (Is(50)), unit weight (γ) and shear strength parameters of the discontinuities were evaluated in accordance with the methods suggested by the ISRM (1981, 1985). Pertinent results are summarized in Table 2. The average uniaxial compressive strength of diabases is 93.85 MPa, modulus of elasticity is 25.63 GPa, Poisson's ratio is 0.261, point load strength index is 5.37 MPa, unit weight is 29.08 kN/m3, peak cohesion of joints is 50 kPa, residual cohesion of joints is 38 kPa, peak friction angle of joints is 41° and residual friction angle of joints is 39°.

controlled by discontinuities is likely, the stability must be evaluated by a limit equilibrium analysis, which considers the shear strength along the failure surface, the effects of pore water pressure and the influence of external forces such as reinforcing elements or seismic accelerations (Turner and Schuster, 1996). Additionally, the results appeared form kinematical and limit equilibrium analyses are performed using numerical methods to confirm if slope is stable. In this study, the kinematical analysis and finite element method are done for the right and left slopes which will cut at the dam site.

3. Assessment of rock slope stability

Assessment of slope stability in rocks is usually done through kinematical analyses, limit equilibrium analyses and numerical methods such as finite element method. If the kinematical analysis indicates that the failure

Fig. 4. Kinematical analysis of the right and left slopes.

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Table 3 Modes of failures and safe slope angles based on kinematic analysis Slope orientation

Joint set

Joint direction

Probable failure mode

Safe slope angle (°)

Right slope

27/60

78

27/240

68/75 78/185 85/143 68/75 78/185 85/143

None

Left slope

J1 J2 J3 J1 J2 J3

None

66

3.1. Kinematical analysis

For the kinematical analyses, the lower hemispheres stereographical projection method described by Hoek and Bray (1981) and by Goodman (1989) was used. Planar and wedge failure modes were kinematically studied. Planar failure occurs if the discontinuity plane daylight into the slope face and the difference between the strike of the discontinuity plane and that of the slope face is 20° or less. Wedge failure occurs if the discontinuity intersection vector falls within the critical wedge region, which is bounded by the great circle representing the dip of the slope face and the circle representing the angle of internal friction (ϕ). The rock slopes having different orientation and height will be cut at the dam site during construction of the Kapikaya dam. It is important to determine if these rock slopes are safe. The right slope will have a slope angle of 27° and dip direction angle of 60° and the left slope will have a slope angle of 27° and dip direction angle of 240°. Kinematical analyses were performed for planar and wedge failures using a commercially available software, DIPS 5.0 (Rocscience, 1999) for the right and left slopes at the dam site. Because toppling failure occurs in highly persistent joint and the diabases have low persistent joints at the dam site, kinematical analyses were not performed for toppling failure. The peak friction angle of joints obtained from the laboratory tests was used for the kinematical analyses. During kinematical analyses, the optimum slope angle was determined for planar and wedge failures. Kinematical analyses of the right and left slopes at the dam site are shown in Fig. 4. The parameters used in the analyses and a summary of these analyses are given in

Table 3. Based on the results of the kinematical analyses, no failure is expected for the right and left slopes with slope angle of 27° at the dam site. 3.2. Numerical analysis

In geotechnical engineering, stable permanent slopes are important criteria for safety and cost. Kinematical analyses are helpful only in determining possible kinematic type of failure such as planar, wedge and toppling. They do not consider forces acting on a slope forming material, height of slope and important geotechnical parameters such as cohesion of discontinuities and unit weight. Furthermore, kinematical analysis sometimes does not work for rock having close–very close spaced and low persistent joints, and rotational failure is expected. In these cases, safety of slopes is usually analyzed in engineering practice by numerical approach that provides a direct measure of stability in terms of the factor of safety. In this study, to analyze the stability of slopes at the dam site, a two-dimensional hybrid element model, called Phase2 Finite Element Program (Rocscience, 2006), was used in the numerical analysis conducted here in. The program is based on the finite element method including some geotechnical parameters. These geotechnical parameters are slope height, slope angle, uniaxial compressive strength, Poisson's ratio, unit weight of the rock, Geological strength index (GSI), Hoek –Brown parameters, deformation modulus of rock mass, friction angle, cohesion and direction of the discontinuities and groundwater condition. The value of GSI was obtained from the last form of the quantitative GSI chart, which was proposed by Marinos and Hoek (2000). The Hoek and Brown (1997)

Table 4 The parameters used in numerical analysis GSI

52

Hoek– Brown parameters mi

m b

s

a

15

2.701

0.0048

0.505

Deformation modulus ( E mass, GPa)

Slope height (m)

Slope angle (°)

Right

Left

Right

Left

8.86

68

85

27

27

23


Fig. 5. Shear strength reduction analysis of the right and left slopes.

failure criterion was used for determining the rock mass properties of diabase at the dam site. Hoek et al. (2002) suggested the following equations for calculating the rock mass constants (i.e., m b, s and a):





GSI À 100 ; m b ¼ mi exp 28 À 14 D



ð3 Þ

a¼

1 1 ÀGSI=15 þ e À eÀ20=3 2 6



E mass ¼ E i 0:02 þ



GSI À 100 s ¼ exp ; 9 À 3 D



where D is a factor that depends upon the degree of disturbance to which the rock mass is subjected to by blast damage and stress relaxation tests. In this study, the value of D is considered as zero. The strength of rock masses was calculated from the following equation suggested by Hoek and Diederichs (2006):

ð4 Þ

;

ð5 Þ

1 1 þ eð60þ15 DÀGSIÞ=11



ð6Þ

The rock mass and slopes properties used in the analysis are presented in Tables 2 and 4. Shear strength reduction analyses was carried out using Phase2 for the

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Table 5 Mean discontinuity spacing, discontinuity spacing index ( I f ), point load strength index (Is(50)) and excavatability classes of diabases Slope

Right Left

Mean discontinuity spacing (m) J−1

J−2

J−3

0.046 0.075

0.068 0.095

0.980 0.146

right and left slopes at the dam site and determined Strength Reduction Factor (SRF) for each slope. According to the results of numerical analysis, the Strength Reduction Factor (SRF) of the right and left slopes are 8.08 and 6.5 respectively (Fig. 5) and any rotational failure will not occur. 4. Assessment of rock excavatability

The excavatability of rock depends on the geotechnical properties of the material, on the method of working, and on the type and size of excavation equipment used. It is generally accepted that discontinuity spacing and the strength of the intact rock are particularly important properties. The aperture, infilling and the wall strength of the discontinuities are also important factors. The main excavation methods are blasting, ripping and digging. A number of methods are suggested in the literature to assess the rock excavatability. Each system considers a different set of geotechnical parameters. The graph suggested by Franklin et al. (1971) considered only two parameters: fracture (joint) spacing index, I f, and point load strength index, I s. Ripper performance charts published by Caterpillar (1988) considered only seismic velocity. Weaver (1975) proposed a ‘rippability rating chart ’. This chart was adapted from the Rock Mass Rating (RMR)system used fortunnel support design (Bieniawski, 1974). The main changes were the replacement of Rock Quality Designation (RQD) with seismic velocity, the introduction of a weathering parameter and adjustments for the effects of discontinuity orientation. Kirsten (1982) proposed an ‘excavatability index’, N , based on the Q system for tunneling (Barton et al., 1974). He also suggested adjustment for discontinuity orientation in ripping. Minty and Kearns (1983) modified Weaver's rippability rating chart and suggested a ‘geological factors rating’ (GFR) which considers groundwater condition and surface roughness of discontinuities. Scoble and Muftuoglu (1984) devised a ‘digability index’ based on discontinuity spacing, rock strength and weathering.Smith (1986) suggested that the seismic velocity proposed byMinty and Kearns (1983) should be omitted in the evolution. Singh

Discontinuity spacing index ( I f )

Point load strength index (Is(50), MPa)

Excavatability class

0.080 0.098

0.71–7.98 1.94–9.71

Easy ripping Easy–hard ripping

et al. (1987) developed an alternative rippability rating chart. They considered seismic velocity, point load strength index, weathering and discontinuity spacing. Ripper performance charts published in the Caterpillar Performance Handbook (Caterpillar, 1988). These charts consider only seismic velocity of various rock types for assessment of rock excavatability. Karpuz et al. (1990) modified the graph suggested by Franklin et al. (1971) and considered seismic velocity, unconfined compressive strength of intact rock, rock hardness, weathering and discontinuity spacing. Hadjigeorgiou and Scoble (1990) also considered point load strength, weathering, discontinuity spacing and discontinuity orientation in their assessment of excavatability. Kentli and Topal (2004) used to the chart of excavatability for rock suggested by Pettifer and Fookes (1994) and suggested that spacing of rock joints at the deeper levels is also considered due to joint spacing may be increased. In the present study, the revised excavatability chart proposed by Pettifer and Fookes (1994) was used for the assessment of rock excavatability at the dam site. The excavatability chart considers the types of excavation equipment and requires engineering geological parameters such as the discontinuity spacing index ( I f ) and point load strength index (Is(50)). These parameters are relatively easy to obtain through field and laboratory studies. Joint spacing was measured separately for right and left slopes at the dam site and discontinuity spacing index ( I f ) was calculated from the following equation by the ISRM (1981): I f ¼

3 J v

ð7Þ

where J is volumetric joint count and it was calculated from the following equation suggested by the ISRM (1981): v

J v ¼

1 1 1 þ þ S 1 S 2 S 3

ð8Þ

where S 1, S 2 and S 3 are discontinuity spacing of joint sets.


25

Fig. 6. Excavatability assessment chart (Pettifer and Fookes, 1994) of the rock in the study area.

For the point load strength index, Is(50), a total of 54 samples from collected right and left slopes were tested in accordance with the ISRM method (ISRM, 1985), and their values were used to determine for excavatability of the right and left slopes at the dam site. The parameters used are presented in Table 5. The plotting of the data in the revised excavatability chart for diabases is shown in Fig. 6. Based on the excavatability analysis of diabases, the excavatability category of diabases at the right slope is generally easy ripping. However, it is hard ripping and easy ripping for the left slopes at the dam site.

5. Concluding remarks

This study is aimed at assessing the stability and excavatability of diabases at the Kapikaya dam site, which is under construction on the Mamikan stream in eastern Turkey. Based on the information collected in the field and laboratory, the slope stability and excavatability of diabases were investigated. The kinematical and numerical analyses were carried out to determine slope stability at the dam site. The excavatability assessment chart proposed by Pettifer and Fookes (1994) was used for determining the excavatability of diabases.

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The kinematical analyses of the slopes indicated that no failure is expected for the right and left slopes at the dam site. According to kinematical analysis, the safe slope angles are 78° and 66° for right and left slopes respectively. However, the diabases include close–very close spaced and low persistent joints at dam site and rotational failure can be expected. Shear strength reduction analyses was evaluated using Phase2 if rotational failure is to occur and determined Strength Reduction Factor (SRF) for the right and left slopes at the dam site. According to the results of numerical analysis, Strength Reduction Factor (SRF) of the right and left slopes are 8.08 and 6.5 respectively and any rotational failure will not occur for the right and left slopes with an angle of 27°. The excavatability analysis reveals that the excavatability of the diabases ranges from hard digging to hard ripping for the right slope. The excavatability for the left slope is generally easy ripping. However, these excavatability ranges are valid for surface or upper levels. Due to weathering and surface conditions, the joint spacing and point load index values at the upper levels may be less than the values at the deeper levels. Thus, it was obtained from a drilling core investigation that the joint spacing decreases at the deeper levels. As a result of this, excavatability of diabases ranges from hard digging to hard ripping for the right and left slope at the dam site. References Bieniawski, Z.T., 1974. Geomechanics classification of rock masses and its application in tunneling. Proceedings of the Third International Congress on Rock Mechanics, vol. 11A. International Society of Rock Mechanics, Denver, pp. 27–32. Barton, N.R., Lien, R., Lunde, J., 1974. Engineering classification of rock masses for the design of tunnel support. Rock Mechanics 4, 189–239. Caterpillar, 1988. Caterpillar Performance Handbook, 19th ed. Caterpillar Tractor Company, Peoria, IL, USA. Deere, D.U., 1964. Technical description of rock cores for engineering purposes. Rock Mechanics and Rock Engineering 1, 17–22. Franklin, J.A., Broch, E., Walton, G., 1971. Logging the mechanical character of rock. Transactions of the Institution of Mining and Metallurgy 80A, 1–9. General Directorate of State Hydraulic Works (DSI), 1991. Planning report of the Kapikaya dam (Malatya), IX. Region Directorate of the State Hydraulic Works, Elazig, Turkey. Goodman, R.E., 1989. Introduction to Rock Mechanics, 2nd edition. Wiley, New York. 562 pp. Hadjigeorgiou, J., Scoble, M.J., 1990. Ground characterization for assessment of ease of excavation. In: Singhal, R.K., Vavra, M. (Eds.), Proceedings of the 4th International Symposium on Mine Planning and Equipment Selection, Calgary, AB. Balkema, Rotterdam, pp. 323–331. Hoek, E., Bray, J.W., 1981. Rock Slope Engineering, 3rd ed. Institute of Mining and Metallurgy, London. 358 pp.

Hoek, E., Brown, E.T., 1997. Practical estimates of rock mass strength. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts 27 (3), 227–229. Hoek, E., Diederichs, M.S., 2006. Empirical estimation of rock mass modulus. International Journal of Rock Mechanics and Mining Sciences 43, 203–215. Hoek, E., Carranza-Torres, C., Corkum, B., 2002. Hoek –Brown Failure Criterion-2002 Edition. In: Hammah, R., Bawden, W., Curran, J., Telesnicki, M. (Eds.), Proceedings of NARMSTAC 2002, Mining Innovation and Technology. Toronto-10 July2002. University of Toronto, pp. 267–273. International Society for Rock Mechanics ISRM, 1981. Rock characterization, testing and monitoring. In: Brown, E.T. (Ed.), ISRM Suggested Methods. Pergamon Press, Oxford, p. 211. International Society for Rock Mechanics ISRM, 1985. Point load test, suggested method for determining point load strength. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts 22, 51–60. Karpuz, C., Pasamehmetoglu, A.G., Bozdag, T., Muftuoglu, Y., 1990. Rippability assessment in surface coal mining. In: Singhal, R.K., Vavra, M. (Eds.), Proceedings of the 4th International Symposium on Mine Planning and Equipment Selection, Calgary, AB. Balkema, Rotterdam, pp. 315–322. Kentli, B., Topal, T., 2004. Assessment of rock slope stability for a segment of the Ankara–Pozanti motorway, Turkey. Engineering Geology 74, 73–90. Kirsten, H.A.D., 1982. A classification system for excavation in natural materials. Civil Engineer in South Africa 24, 293 –308. MacGregor, F., Fell, R., Mostyn, G.R., Hocking, G., McNally, G., 1994. The estimation of rock rippability. Quarterly Journal of Engineering Geology 27, 123–144. Marinos, P., Hoek, E., 2000. GSI: a geologically friendly tool for rock mass strength estimation. Proceedings of the GeoEng2000 at the Int Conference on Geotechnical and Geological Engineering, Melbourne. Technomic publishers, Lancaster, pp. 1422–1446. Miller, R.P., 1965. Engineering classification and index properties for intact rock. Ph.D Thesis. University of Illinois. Minty, E.J., Kearns, G.K., 1983. Rock mass workability. In: Knight, M.J., Minty, E.J., Smith, R.B. (Eds.), Collected Case Studies in Engineering Geology. Geological Society of Australia, Special Publication, vol. 11, pp. 59–81. Pettifer, G.S., Fookes, P.G., 1994. A revision of the graphical method for assessing the excavatability of rock. Quarterly Journal of Engineering Geology 27, 145–164. Rocscience, 1999. DIPS 5.0-Graphical and Statistical Analysis of Orientation Data Rocscience, Canada. 90 pp. Rocscience, 2006. A 2D finite element program for calculating stresses and estimating support around the underground excavations. Geomechanics Software and Research, Rocscience Inc., Toronto, Ontario, Canada. Scoble, M.J., Muftuoglu, Y.V., 1984. Derivation of a diggability index for surface mine equipment selection. Mining Science and Technology 1, 305–322. Smith, H.J., 1986. Estimating rippability by rock mass classification. Proceedings of the 27th U.S. Symposium on Rock Mechanics, Tuscaloosa, AL. AIME, New York, pp. 443 –448. Singh, B., Gahrooee, D.R., 1989. Application of rock mass weakening coefficient for stability assessment of slopes in heavily jointed rock masses. International Journal of Surface Mining, Reclamation and Environment 3, 217–219. Singh, R.N., Denby, B., Egretli, I., 1987. Development of a new rippability index for coal measures excavations. Proceedings of the


28th U.S. Symposium on Rock Mechanics, Tucson, AZ. Balkema, Boston, pp. 935–943. Turner, A.K., Schuster, R.L., 1996. Landslides—Investigation and Mitigation. Transportation Research Board, National Research Council, Special Report, vol. 247. National Academy Press, Washington, DC, p. 673.

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Weaver, J.M., 1975. Geological factors significant in the assessment of rippability. Civil Engineer in South Africa 17, 313–316. Yazgan, E., 1984. Geodynamic evolution of the Eastern Taurus region. Int Symposium on the Geology of the Taurus Belt, Proceedings, Ankara, pp. 199–208.

Rock Slope Stability and Excavatability

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