Rock slope stability and excavatability assessment of rocks at theKapikaya dam site, Turkey
Zulfu Gurocak a,⁎, Selcuk Alemdag a, Musharraf M. Zaman b
a Department of Geology, Firat University, Elazig, 23119, Turkeyb 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 2007Available 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 werecarried out to determine uniaxial compressive strength, Young's modulus, unit weight, point load strength index and shear strengthparameters of discontinuities.
The slope stability and excavatability of rocks is animportant problem in geotechnical engineering. Thisholds for both the design and construction stages.Currently, a number of methods are being used for theassessment of slope stability and excavatability (Hoekand Bray, 1981; Goodman, 1989; Pettifer and Fookes,
1994). Kinematical, limit equilibrium and numericalanalyses are generally preferred for the evaluation ofrock. Kinematical analysis refers to the motion of bodieswithout reference to the forces that cause them to move.Equilibrium analyses consider the shear strength alongthe failure surface, the effects of pore water pressure andthe influence of external forces such as reinforcingelements or seismic accelerations. On the other hand,numerical analyses such as finite element and distinctelement methods are performed to confirm resultsoccurred from kinematical and equilibrium analysis. Anumber of methods have been suggested by researchers(Kirsten, 1982; Minty and Kearns, 1983; Caterpillar,1988; Hadjigeorgiou and Scoble, 1990; Karpuz et al.,
18 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 ofthese methods considers a different set of geotechnicalparameters such as seismic velocity, point load strengthindex,weathering, discontinuity spacing and groundwater.
The field site used in this study is located about 30 kmeast of Malatya, Turkey (Fig. 1). The Kapikaya dam,which is under construction on the Mamikan stream, islocated at this site. The dam project is designed toregulate drainage and irrigate agricultural lands belong-ing to the Kale plain. The design of the Kapikaya damproject is under the supervision of the GeneralDirectorate of State Hydraulic Works (1991), theMinistry of Energy and Natural Resources in Turkey.The dam site is located within the Ispendere Ophiolites,which is composed of diabases. Geological mapping andgeotechnical descriptions were conducted in the field.
The physical, mechanical and elastic properties of therocks under consideration were determined fromlaboratory testing on intact rock samples. These testsinclude an evaluation of uniaxial compressive strength(σc), Young's modulus (E), Poisson's ratio (v), pointload strength index (Is(50)) and unit weight (γ). The mainorientation, spacing, persistence, aperture, filling,weathering and roughness of discontinuities were de-scribed using the scan-line survey method following theISRM (1981) description criteria. Kinematical and finite
Fig. 1. The location map
element method analyses were performed for right andleft slopes at the dam site. The method suggested byPettifer and Fookes (1994) was used for the assessmentof rock excavatability.
2. Geology, field and laboratory studies
The study area is located approximately 30 km east ofMalatya in eastern Turkey (Fig. 1) where the Kapikayadam site is under construction on the Mamikan stream.Units of various ages from the Upper Jurassic to theQuaternary are exposed in the region. Upper Jurassic–Lower Cretaceous ophiolitic rocks are exposed at theKapikaya dam site (Yazgan, 1984). These rocks are partof the extensive Jurassic–Cretaceous aged ophioliticcomplex in the Southeast Anatolian Thrust Zone. Theseophiolitic rocks are found as allochthonous bodies in theEastern Taurus. The ophiolitic rocks which consist ofdiabases in the study area are a part of IspendereOphiolites. Also, these rocks are called sheeted dykecomplex. The diabases are yellowish-grey color and welljointed. Although the diabases are moderately weatheredon the upper levels, they are slightly weathered on thelower levels at the dam site. These rocks are cut by singlediabase dykes having a dark grey color and a thickness of20–75 cm. Diabases are primarily composed of finegrained plagioclase and clinopyroxene crystals. Some
of the study area.
19Z. Gurocak et al. / Engineering Geology 96 (2008) 17–27
carbonatization of plagioclases and cloritization ofclinopyroxcene can be detected at the site.
Overlying the mainly Upper Jurassic–Lower Creta-ceous deposits are talus and alluvial materials. Talusdisplays a wide distribution in the study area (Fig. 2).Talus is originated from diabases blocks with clayeymatrix and is observed on both the right and the leftbanks of the dam site. From the drillings conducted bythe General Directorate of State Hydraulic Works (DSI,1991) at the dam site, the thicknesses of talus depositswere 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 thestudy area. These deposits consist of gravel, sand and
Fig. 2. The geological ma
silt. From the drillings conducted by the GeneralDirectorate of State Hydraulic Works (DSI, 1991) atthe dam site, the thicknesses of alluvium deposits werefound to vary between 1 and 6 m.
During the field surveys, engineering geological mapof the Kapikaya dam site was constituted. The fieldstudies also included measurements of orientation,persistence, spacing, aperture, and roughness, degree ofweathering and filling of discontinuities in the diabases.
In addition, an examination was made of the 722 m ofcore from 16 boreholes drilled to determinate engineeringgeological properties on vertical and horizontal directionsof rocks such as RQD, permeability andweathering by theGeneralDirectorate of State HydraulicWorks (DSI, 1991).
p of the study area.
Table 1The percentage distribution of RQD values of diabases
RQD Rock quality Distribution %
0–25 Very poor 325–50 Poor 1050–75 Fair 3075–90 Good 4090–100 Excellent 17
20 Z. Gurocak et al. / Engineering Geology 96 (2008) 17–27
The locations of the boreholes were plotted on thegeological map of the dam site (Fig. 2). The RQD valuesof 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 valuesincrease at deeper levels, the RQD values of diabasesincrease at the deeper levels. Furthermore, these joints arenot filled by filling material such as clay, calcite at thedeeper levels contrary to the upper levels.
Engineering geological properties of the rocks ex-posed in the study area were determined on the basis offield observations/measurements and laboratory tests.The description of rock material and mass character-istics 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 elas-ticity intact rocks (E), Poisson's ratio (v), point loadstrength index (Is(50)), unit weight (γ) and shear strengthparameters of the joints by direct shear tests were de-termined in accordance with the ISRM methods (ISRM,1981, 1985).
As the study area is located in a seismically activeregion, the diabases exposed around the Kapikaya dam
Table 2Material of diabases and joints properties
Property Number of tests
Uniaxial compressive strength (σc, MPa) 62Young's modulus of intact rock (E, GPa) 28Poisson's ratio 28Point load strength index (Is(50), MPa) 54Unit weight (γ, kN/m3) 62RQD (%)Joint set number Three joint sets plus raSpacing of discontinuities (mm) 18–197 (average 120)Persistence of discontinuities (m) Generally 1–3 m, howAperture of discontinuities (mm) Generally N5 mm, howRoughness of discontinuities Generally rough, howeInfilling Generally calcite havinWeathering degree Generally slightly weaGroundwater conditions Generally dry occasion
site contain systematic joint sets. Table 2 shows the mainorientation, spacing, persistence, aperture and roughnessof discontinuities. These were described using the scan-line survey method following the ISRM (1981)description criteria.
The degree of weathering of the discontinuoussurfaces was assessed using the Schmidt hammer, andthe weathering index was calculated from the followingequation by Singh and Gahrooee (1989):
Wc ¼ rcJCS
ð1Þ
where
σc Uniaxial compressive strength of fresh rock(MPa), and
JCS Strength of discontinuity surface (MPa).
The strength of discontinuity surface (JCS) wascalculated from the following equation by Miller(1965):
Log JCS ¼ 0:00088gRþ 1:01 ð2Þ
where
γ Bulk volume weight (kN/m3), andR Hardness value from rebounding of the Schmidt
hammer.
In the study area, a total of 846 joint measurementswere taken from diabases. Discontinuity orientationswere processed utilizing a commercially availablesoftware DIPS 5.0 (Rocscience, 1999), based on equal-angle stereographic projection, and major joint sets were
ever occasionally b1 m and 10–20 mever occasionally 0.1–0.5 mmver occasionally smoothg a thickness of N5 mm, however occasionally b5 mm calcitethered, occasionally moderately weatheredally damp
Fig. 3. Stereographic projection of joint sets in diabases.
Fig. 4. Kinematical analysis of the right and left slopes.
21Z. Gurocak et al. / Engineering Geology 96 (2008) 17–27
distinguished for diabases (Fig. 3). The major orienta-tions of the joint sets for diabases are listed below:
Joint set 1: 68/75Joint set 2: 78/185Joint set 3: 85/143
According to the ISRM (1981), the joint sets in thediabases have close to very close spacing, low persistenceand rough-planar. While these joint sets are open andmoderately weathered character at the surface, they aretight and slightly weathered character at deeper levels.
Uniaxial compressive strength (σc), modulus ofelasticity of intact rock (E), Poisson's ratio (v), pointload strength index (Is(50)), unit weight (γ) and shearstrength parameters of the discontinuities were evaluat-ed in accordance with the methods suggested by theISRM (1981, 1985). Pertinent results are summarizedin Table 2. The average uniaxial compressive strength ofdiabases is 93.85 MPa, modulus of elasticity is25.63 GPa, Poisson's ratio is 0.261, point load strengthindex is 5.37 MPa, unit weight is 29.08 kN/m3, peakcohesion of joints is 50 kPa, residual cohesion of jointsis 38 kPa, peak friction angle of joints is 41° and residualfriction angle of joints is 39°.
3. Assessment of rock slope stability
Assessment of slope stability in rocks is usually donethrough kinematical analyses, limit equilibrium analysesand numerical methods such as finite element method. Ifthe kinematical analysis indicates that the failure
controlled by discontinuities is likely, the stability mustbe evaluated by a limit equilibrium analysis, whichconsiders the shear strength along the failure surface, theeffects of porewater pressure and the influence of externalforces such as reinforcing elements or seismic accelera-tions (Turner and Schuster, 1996). Additionally, theresults appeared form kinematical and limit equilibriumanalyses are performed using numerical methods toconfirm if slope is stable.
In this study, the kinematical analysis and finite elementmethod are done for the right and left slopeswhichwill cutat the dam site.
Table 3Modes 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 J1 68/75 None 78J2 78/185J3 85/143
Left slope 27/240 J1 68/75 None 66J2 78/185J3 85/143
22 Z. Gurocak et al. / Engineering Geology 96 (2008) 17–27
3.1. Kinematical analysis
For the kinematical analyses, the lower hemispheresstereographical projection method described by Hoekand Bray (1981) and by Goodman (1989) was used.Planar and wedge failure modes were kinematicallystudied. Planar failure occurs if the discontinuity planedaylight into the slope face and the difference betweenthe strike of the discontinuity plane and that of the slopeface is 20° or less. Wedge failure occurs if thediscontinuity intersection vector falls within the criticalwedge region, which is bounded by the great circlerepresenting the dip of the slope face and the circlerepresenting the angle of internal friction (ϕ).
The rock slopes having different orientation andheight will be cut at the dam site during construction ofthe Kapikaya dam. It is important to determine if theserock slopes are safe. The right slope will have a slopeangle of 27° and dip direction angle of 60° and the leftslope will have a slope angle of 27° and dip directionangle of 240°.
Kinematical analyses were performed for planar andwedge failures using a commercially available software,DIPS 5.0 (Rocscience, 1999) for the right and left slopesat the dam site. Because toppling failure occurs in highlypersistent joint and the diabases have low persistentjoints at the dam site, kinematical analyses were notperformed for toppling failure. The peak friction angleof joints obtained from the laboratory tests was used forthe kinematical analyses.
During kinematical analyses, the optimum slopeangle was determined for planar and wedge failures.Kinematical analyses of the right and left slopes at thedam site are shown in Fig. 4. The parameters used in theanalyses and a summary of these analyses are given in
Table 4The parameters used in numerical analysis
GSI Hoek–Brown parameters Dm(E
mi mb s a
52 15 2.701 0.0048 0.505 8.
Table 3. Based on the results of the kinematicalanalyses, no failure is expected for the right and leftslopes with slope angle of 27° at the dam site.
3.2. Numerical analysis
In geotechnical engineering, stable permanent slopesare important criteria for safety and cost. Kinematicalanalyses are helpful only in determining possiblekinematic type of failure such as planar, wedge andtoppling. They do not consider forces acting on a slopeforming material, height of slope and importantgeotechnical parameters such as cohesion of disconti-nuities and unit weight. Furthermore, kinematicalanalysis sometimes does not work for rock havingclose–very close spaced and low persistent joints, androtational failure is expected. In these cases, safety ofslopes is usually analyzed in engineering practice bynumerical approach that provides a direct measure ofstability in terms of the factor of safety.
In this study, to analyze the stability of slopes at thedam site, a two-dimensional hybrid element model,called Phase2 Finite Element Program (Rocscience,2006), was used in the numerical analysis conductedhere in. The program is based on the finite elementmethod including some geotechnical parameters. Thesegeotechnical parameters are slope height, slope angle,uniaxial compressive strength, Poisson's ratio, unitweight of the rock, Geological strength index (GSI),Hoek–Brown parameters, deformation modulus of rockmass, friction angle, cohesion and direction of thediscontinuities and groundwater condition.
The value of GSI was obtained from the last form ofthe quantitative GSI chart, which was proposed byMarinos and Hoek (2000). The Hoek and Brown (1997)
eformationodulus
mass, GPa)
Slope height (m) Slope angle (°)
Right Left Right Left
86 68 85 27 27
Fig. 5. Shear strength reduction analysis of the right and left slopes.
23Z. Gurocak et al. / Engineering Geology 96 (2008) 17–27
failure criterion was used for determining the rock massproperties of diabase at the dam site. Hoek et al. (2002)suggested the following equations for calculating therock mass constants (i.e., mb, s and a):
mb ¼ miexpGSI� 10028� 14D
� �; ð3Þ
s ¼ expGSI� 1009� 3D
� �; ð4Þ
a ¼ 12þ 16
e�GSI=15 � e�20=3� �
; ð5Þ
where D is a factor that depends upon the degree ofdisturbance to which the rock mass is subjected to byblast damage and stress relaxation tests. In this study, thevalue of D is considered as zero. The strength of rockmasses was calculated from the following equationsuggested by Hoek and Diederichs (2006):
Emass ¼ Ei 0:02þ 1
1þ e 60þ15D�GSIð Þ=11
� �ð6Þ
The rock mass and slopes properties used in theanalysis are presented in Tables 2 and 4. Shear strengthreduction analyses was carried out using Phase2 for the
Table 5Mean discontinuity spacing, discontinuity spacing index (If), point load strength index (Is(50)) and excavatability classes of diabases
Slope Mean discontinuity spacing (m) Discontinuityspacingindex (If)
24 Z. Gurocak et al. / Engineering Geology 96 (2008) 17–27
right and left slopes at the dam site and determinedStrength Reduction Factor (SRF) for each slope.According to the results of numerical analysis, theStrength Reduction Factor (SRF) of the right and leftslopes are 8.08 and 6.5 respectively (Fig. 5) and anyrotational failure will not occur.
4. Assessment of rock excavatability
The excavatability of rock depends on the geotechnicalproperties of the material, on the method of working, andon the type and size of excavation equipment used. It isgenerally accepted that discontinuity spacing and thestrength of the intact rock are particularly importantproperties. The aperture, infilling and the wall strength ofthe discontinuities are also important factors. The mainexcavation methods are blasting, ripping and digging. Anumber ofmethods are suggested in the literature to assessthe rock excavatability. Each system considers a differentset of geotechnical parameters.
The graph suggested by Franklin et al. (1971)considered only two parameters: fracture (joint) spacingindex, If, and point load strength index, Is. Ripper perform-ance charts published by Caterpillar (1988) consideredonly seismic velocity. Weaver (1975) proposed a ‘ripp-ability rating chart’. This chart was adapted from the RockMassRating (RMR) systemused for tunnel support design(Bieniawski, 1974). The main changes were the replace-ment of Rock Quality Designation (RQD) with seismicvelocity, the introduction of a weathering parameter andadjustments 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 orientationin ripping. Minty and Kearns (1983) modified Weaver'srippability rating chart and suggested a ‘geological factorsrating’ (GFR) which considers groundwater condition andsurface roughness of discontinuities. Scoble and Muftuo-glu (1984) devised a ‘digability index’ based on disconti-nuity spacing, rock strength and weathering. Smith (1986)suggested that the seismic velocity proposed byMinty andKearns (1983) should be omitted in the evolution. Singh
et al. (1987) developed an alternative rippability ratingchart. They considered seismic velocity, point loadstrength index, weathering and discontinuity spacing.Ripper performance charts published in the CaterpillarPerformance Handbook (Caterpillar, 1988). These chartsconsider only seismic velocity of various rock types forassessment of rock excavatability. Karpuz et al. (1990)modified the graph suggested by Franklin et al. (1971) andconsidered seismic velocity, unconfined compressivestrength of intact rock, rock hardness, weathering anddiscontinuity spacing. Hadjigeorgiou and Scoble (1990)also considered point load strength, weathering, discon-tinuity spacing and discontinuity orientation in theirassessment of excavatability. Kentli and Topal (2004)used to the chart of excavatability for rock suggested byPettifer and Fookes (1994) and suggested that spacing ofrock joints at the deeper levels is also considered due tojoint spacing may be increased.
In the present study, the revised excavatability chartproposed by Pettifer and Fookes (1994) was used for theassessment of rock excavatability at the dam site. Theexcavatability chart considers the types of excavationequipment and requires engineering geological para-meters such as the discontinuity spacing index (If) andpoint load strength index (Is(50)). These parameters arerelatively easy to obtain through field and laboratorystudies. Joint spacing was measured separately for rightand left slopes at the dam site and discontinuity spacingindex (If) was calculated from the following equation bythe ISRM (1981):
If ¼ 3Jv
ð7Þ
where Jv is volumetric joint count and it was calculatedfrom the following equation suggested by the ISRM(1981):
Jv ¼ 1S1
þ 1S2
þ 1S3
ð8Þ
where S1, S2 and S3 are discontinuity spacing of jointsets.
Fig. 6. Excavatability assessment chart (Pettifer and Fookes, 1994) of the rock in the study area.
25Z. Gurocak et al. / Engineering Geology 96 (2008) 17–27
For the point load strength index, Is(50), a total of 54samples from collected right and left slopes were testedin accordance with the ISRMmethod (ISRM, 1985), andtheir values were used to determine for excavatability ofthe right and left slopes at the dam site. The parametersused are presented in Table 5.
The plotting of the data in the revised excavatabilitychart for diabases is shown in Fig. 6. Based on theexcavatability analysis of diabases, the excavatabilitycategory of diabases at the right slope is generally easyripping. However, it is hard ripping and easy ripping forthe left slopes at the dam site.
5. Concluding remarks
This study is aimed at assessing the stability andexcavatability of diabases at the Kapikaya dam site, whichis under construction on the Mamikan stream in easternTurkey. Based on the information collected in the fieldand laboratory, the slope stability and excavatability ofdiabases were investigated. The kinematical and numer-ical analyses were carried out to determine slope stabilityat the dam site. The excavatability assessment chartproposed by Pettifer and Fookes (1994) was used fordetermining the excavatability of diabases.
26 Z. Gurocak et al. / Engineering Geology 96 (2008) 17–27
The kinematical analyses of the slopes indicated thatno failure is expected for the right and left slopes at thedam site. According to kinematical analysis, the safeslope angles are 78° and 66° for right and left slopesrespectively. However, the diabases include close–veryclose spaced and low persistent joints at dam site androtational failure can be expected.
Shear strength reduction analyses was evaluatedusing Phase2 if rotational failure is to occur anddetermined Strength Reduction Factor (SRF) for theright and left slopes at the dam site. According to theresults of numerical analysis, Strength Reduction Factor(SRF) of the right and left slopes are 8.08 and 6.5respectively and any rotational failure will not occur forthe right and left slopes with an angle of 27°.
The excavatability analysis reveals that the excavat-ability of the diabases ranges from hard digging to hardripping for the right slope. The excavatability for the leftslope is generally easy ripping. However, these excavat-ability ranges are valid for surface or upper levels. Due toweathering and surface conditions, the joint spacing andpoint load index values at the upper levels may be lessthan the values at the deeper levels. Thus, it was obtainedfrom a drilling core investigation that the joint spacingdecreases at the deeper levels. As a result of this,excavatability of diabases ranges from hard digging tohard ripping for the right and left slope at the dam site.
References
Bieniawski, Z.T., 1974. Geomechanics classification of rock massesand its application in tunneling. Proceedings of the ThirdInternational Congress on RockMechanics, vol. 11A. InternationalSociety of Rock Mechanics, Denver, pp. 27–32.
Barton, N.R., Lien, R., Lunde, J., 1974. Engineering classification ofrock 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 engineeringpurposes. Rock Mechanics and Rock Engineering 1, 17–22.
Franklin, J.A., Broch, E., Walton, G., 1971. Logging the mechanicalcharacter of rock. Transactions of the Institution of Mining andMetallurgy 80A, 1–9.
General Directorate of State Hydraulic Works (DSI), 1991. Planningreport of the Kapikaya dam (Malatya), IX. Region Directorate ofthe 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 forassessment of ease of excavation. In: Singhal, R.K., Vavra, M.(Eds.), Proceedings of the 4th International Symposium on MinePlanning and Equipment Selection, Calgary, AB. Balkema,Rotterdam, pp. 323–331.
Hoek, E., Bray, J.W., 1981. Rock Slope Engineering, 3rd ed. Instituteof 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 massmodulus. International Journal of Rock Mechanics and MiningSciences 43, 203–215.
Hoek, E., Carranza-Torres, C., Corkum, B., 2002. Hoek–BrownFailure Criterion-2002 Edition. In: Hammah, R., Bawden, W.,Curran, J., Telesnicki, M. (Eds.), Proceedings of NARMSTAC2002, Mining Innovation and Technology. Toronto-10 July2002.University of Toronto, pp. 267–273.
International Society for Rock Mechanics ISRM, 1981. Rockcharacterization, 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. Interna-tional 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 Symposiumon Mine Planning and Equipment Selection, Calgary, AB.Balkema, Rotterdam, pp. 315–322.
Kentli, B., Topal, T., 2004. Assessment of rock slope stability for asegment of the Ankara–Pozanti motorway, Turkey. EngineeringGeology 74, 73–90.
Kirsten, H.A.D., 1982. A classification system for excavation innatural 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 ofEngineering Geology 27, 123–144.
Marinos, P., Hoek, E., 2000. GSI: a geologically friendly tool for rockmass strength estimation. Proceedings of the GeoEng2000 at theInt Conference on Geotechnical and Geological Engineering,Melbourne. Technomic publishers, Lancaster, pp. 1422–1446.
Miller, R.P., 1965. Engineering classification and index properties forintact 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 inEngineering Geology. Geological Society of Australia, SpecialPublication, vol. 11, pp. 59–81.
Pettifer, G.S., Fookes, P.G., 1994. A revision of the graphical methodfor assessing the excavatability of rock. Quarterly Journal ofEngineering Geology 27, 145–164.
Rocscience, 1999. DIPS 5.0-Graphical and Statistical Analysis ofOrientation Data Rocscience, Canada. 90 pp.
Rocscience, 2006. A 2D finite element program for calculating stressesand 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 indexfor surface mine equipment selection. Mining Science andTechnology 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 weakeningcoefficient for stability assessment of slopes in heavily jointed rockmasses. International Journal of Surface Mining, Reclamation andEnvironment 3, 217–219.
Singh, R.N., Denby, B., Egretli, I., 1987. Development of a newrippability index for coal measures excavations. Proceedings of the
27Z. Gurocak et al. / Engineering Geology 96 (2008) 17–27
28th U.S. Symposium on Rock Mechanics, Tucson, AZ. Balkema,Boston, pp. 935–943.
Turner, A.K., Schuster, R.L., 1996. Landslides—Investigation andMitigation. Transportation Research Board, National ResearchCouncil, Special Report, vol. 247. National Academy Press,Washington, DC, p. 673.
Weaver, J.M., 1975. Geological factors significant in the assessment ofrippability. 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.
