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Research ArticleAssessment of Slope Instability and Risk Analysis ofRoad Cut Slopes in Lashotor Pass Iran

Mohammad Hossein Taherynia1 Mojtaba Mohammadi1 and Rasoul Ajalloeian2

1 Department of Geology Faculty of Science Kharazmi University Karaj 31979-37551 Iran2Department of Geology Faculty of Science University of Isfahan Isfahan 81746-73441 Iran

Correspondence should be addressed to Mohammad Hossein Taherynia mhtaheryniagmailcom

Received 14 October 2013 Accepted 12 February 2014 Published 10 April 2014

Academic Editor Agust Gudmundsson

Copyright copy 2014 Mohammad Hossein Taherynia et al This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

Assessment of the stability of natural and artificial rock slopes is an important topic in the rock mechanics sciences One ofthe most widely used methods for this purpose is the classification of the slope rock mass In the recent decades several rockslope classification systems are presented by many researchers Each one of these rock mass classification systems uses differentparameters and rating systemsThese differences are due to the diversity of affecting parameters and the degree of influence on therock slope stability Another important point in rock slope stability is appraisal hazard and risk analysis In the risk analysis thedegree of danger of rock slope instability is determined The Lashotor pass is located in the Shiraz-Isfahan highway in Iran Fieldsurveys indicate that there are high potentialities of instability in the road cut slopes of the Lashotor pass In the current paper thestability of the rock slopes in the Lashotor pass is studied comprehensively with different classification methods For risk analyseswe estimated dangerous area by use of the RocFall software Furthermore the dangers of falling rocks for the vehicles passing theLashotor pass are estimated according to rockfall hazard rating system

1 Introduction

Appraisal hazard and risk analysis is one of the most impor-tant issues in the rock slopes instability study Risk is ameasure of the probability and severity of adverse effects[1] Risk is the combination of probability of an event andits consequences [2] Therefore for risk analysis of slopeinstability the first step is assessment of the slope instabilitypotential and probability of occurrence of the slope failureand the next step is determination of the consequence anddegree of danger of the slope instability

Rock mass classification is a useful means for the assess-ment of the instability potentialof rock cut slopes basedon the most important inherent and structural parameters[3] The geomechanics classification or the rock mass rating(RMR) introduced by Bieniawski [4] was the first attempt toassess rock slope instability based on rockmass classificationRomana [5] by developing RMR proposed slopemass rating(SMR) classification system especially for rock slopes classi-fication and judgment about slopes stability Slope stability

rating (SSR) system is proposed by Taheri and Tani [6 7]for the characterization of slope stability of heavily jointedrock masses This system is based on the geological strengthindex (GSI) system and the nonlinear Hoek-Brown failurecriterion To provide a more quantitative numerical basis forevaluating the GSI this classification system was modified bySonmez and Ulusay [8] and Sonmez and Ulusay [9] in whichlatest version of the quantitative GSI chart is used in the SSRsystem Since some of themajor slope stability parameters arenot included in GSI in SSR systems besides the geologicalstrength index (GSI) five additional parameters have beentaken into accountThese additional parameters included theuniaxial compressive strength rock type slope excavationmethod groundwater and earthquake force

The RQD parameter is not used in the SSR calcificationsystems This is the most advantage of the SSR comparingto the SMR and other calcification systems (SRMR CSMRGSI VRFSR and FRHI) The RQD is a basic componentof many rock mass classification systems There are severalmajor disadvantages related to RQD definition and the

Hindawi Publishing CorporationJournal of Geological ResearchVolume 2014 Article ID 763598 12 pageshttpdxdoiorg1011552014763598

2 Journal of Geological Research

drilling procedure [3] Furthermore in the RMR and SMRclassification systems are simultaneously used the RQD indexand ldquodiscontinuity spacingrdquo parameter In fact the spacingof discontinuities has double influence on the final rating[10] The other advantage of SSR classification is takeninto account the effect of earthquake force on the slopeinstability This is very important and essential for slopesstability analyses in seismic active zones Iran is located in theAlpine-Himalayan orogenic system and shows high seismicactivity

In many cases spatially in vertical slopes or very steepslopes such as cut slope other types of rock slope failure(wedge failure planer failure and toppling) may eventuallylead to the rockfall event If sliding distance of rock block orrock mass that detached by sliding toppling or falling wasnegligible to descending distance through air it is defined asa rockfall [11] Rockfalls constitute amajor hazard in rock cutsalongside roads inmountainous regions that causes loss of lifeand property because of its very rapid movement [12]

In the past the rockfall simulation was based on experi-ence and extensive in situ rockfall tests [13] Ritchie [14] bycarrying out full scale tests on rockfall event proposed simplechart for determining required width and depth of rock catchditches in relation to height and slope angle Over the lastdecades many computer programs are developed for simula-tion of rockfall [15ndash18] One of themost practical programs ofthese computer programs is the RocFall software that can beused to simulate almost all types of rockfall events [19] Thissoftware provides valuable information about kinetic energyvelocity bounce height and fall-out distance of falling rockfragment that are essential to determine the consequence anddegree of danger of slope instability The RocFall softwarealso can be used to design remedial measures and test theireffectiveness [19]

At the last two decades a number of slope instabilityrisk assessment systems have been developed and rockfallhazard rating system [20] is one of the most well-knownof these systems [21] This method used a simple approachfor assessing and quantifying the risk of rockfalls in thetransportation routes [22] The rockfall hazard rating system(RHRS) contains nine deferent parameters which can bedivided into two groups the parameters that define rockfallhazard (slope height geologic character volume of rock-fallblock size climate and presence of water on slope androckfall history) and the parameters that indicate the vehiclevulnerability (ditch effectiveness average vehicle risk percentof decision sight distance and roadway width) [12]

In this research at the first step the instability potentialof the Lashotor trenches was assessed by use of SMR andSSR classification systems Rock mass classifications indicatehigh instability potential and likely rockfalls in the Lashotorcut slopes Therefore direction speed and energy of thefalling rock fragments are simulated for risk analyses usingthe RocFall software Finally the risk of falling rocks for thevehicles passing the Lashotor pass is estimated by using therockfall hazard rating system

2 General Characteristics of the Study Area

The Lashotor pass was constructed at 1991 in distance of22 km of the Isfahan-Shiraz highway in Iran to eliminate theinappropriate and dangerous curvatures in the Lashotor passand shorten the path As shown in Figure 1 the length ofthe previous way is 688 km while the current path in theLashotor pass is 362 km Also the new road is straighter thanthe previous one Generally this pass has 250 meters lengthand 24 meters width The maximum height of the walls is 34meters and the dips of the cut slopes are about 80 degrees

Geologically the Lashotor pass is located in the Kolah-Ghazi region in the central part of the Sanandaj-Sirjan zoneIn this region 30 to 50 meters of the upper Cretaceouslimestone is lying on the lower Cretaceous shale and marllayers In the central part of the Sanandaj-Sirjan zone thefault pattern consists of major NW-trending longitudinalfaults NE-SW-trending transverse faults and N-S-trendingoblique faults [23] Fault pattern in the study area is shown inFigure 2

The nearest fault to the Lashotor pass is the Kolah-Ghazi fault This fault has several branch minor faultsApproximately 61m offset occurs along the Kolah-Ghazifault where the Quaternary gravel plains and the Holocenealluvial deposits are dissected and dextrally displaced by thefault and its branching minor faults The maximum valueof the slip rate calculated along the Kolah-Ghazi fault isabout 92mmyear [23] Figures 3 and 4 show general view ofthe eastern and western Lashotor cut slopes The movementcaused by fault in the eastern cut slope face is indicated inFigure 3 Figure 4 shows a branch fault of the Kolah-Ghazifault in the southern part of the Lashotor pass

The presence of tectonic structures such as faults andfolds can play significant role in the slope instability [24]According to Pourghasemi et al [25] there is high instabilityprobability of slopes in distance less than 100m of faultsKhaloKakaie and Naghadehi [26] studied slope stability withuse of interaction matrix and estimated proportional shareof sixteen parameters in slope failure According to thesestudies presence of faults and folds played significant role inthe slope failure and its proportional share in slope failure isabout 775

Figure 4 shows an unstable rock wedge in the westernslope that is formed by intersection of the joint sets Theseare just a few of evidences which address the instability of cutslopes in the Lashotor pass The most notable failure in thispass occurred during a constructionwhich caused temporarycessation of excavation [27] The failed part of the westernslope is shown in Figure 5

3 Assessment of Instability Potential andFailure Types of the Slopes

For assessing of instability potential and failure types at thefirst step discontinuity and their spatial orientations in theLashotor slopes were studied According to the strike and dipof the discontinuity in respect to slope face orientation we

Journal of Geological Research 3

N

Trench of Esfahan-Shiraz road

Mobarakeh industrial zone

362km

3km

688 km

N32∘27

99840012

998400998400

N32∘27

99840012

998400998400

51∘45

99840023

998400998400E 51∘45

99840023

998400998400E

Figure 1 The pervious and current roads are shown in the Google Earth image

can determine the probability and type of failure Propertiesand orientation of joints sets and bedding plane in the twowalls of the Lashotor pass are determined in a field survey Atotal of 253 discontinuities were surveyed

Most of the joints have rough surfaces and calcite fillingDeduced information from the field joints study has been

analyzed by using Dips and Swedge software whose resultsare presented in Figures 6 and 7

As shown in Figures 6 and 7 there are five discontinuitiessets (four joint sets and bedding surface) in both walls of theLashotor pass in which intersection of the joint sets formeddifferent unstable wedges in eastern and western walls


Table 1 Value of RMRB in the two slopes of the Lashotor pass

Parameters Western cut slope Eastern cut slopeValue Rating Value Rating

UCS 42MPa 12 42MPa 12RQD 88 17 89 17Joint spacing 13m 15 06m 10Joint condition Slicken sided and 1ndash5mm wide 10 Slicken sided and 1ndash5mm wide 10Ground water condition Damp 10 Damp 10Summation (RMRB) 64 59

Isfahan

Study areaNajafabad

Falavarjan

Foladshahr

Tiran

Zefreh

Yankabad

Borujen

ZarinshahrMobarakeh

Shahreza

MoF

Dehaghan

Reverse-thrust faultNormal faultStrike-slip faultInferred fault

Major faultMinor faultTowns

Khansar FaultDalan fault

Dehaghan faultMain Zagros ThrustSh F

Dif

FFKolah Ghazi fault

Kolah-Ghazi Mountains

BF3BF1

NBFBF2

Ramsheh fault

Qom-Zefreh fault50km

Dehagh fault

Murche Khurt faultN

Figure 2 Fault pattern in the Kolah-Ghazi region [23]

31 Slope Mass Rating (SMR) Classification One of the mostcommon classification systems for evaluation of rock slopestability is the SMR classification The slope mass rating(SMR) is obtained from basic rock mass rating (RMRB)by adding adjustment factors depending on the relativeorientation of joints and slope and adding another factordepending on the method of excavation based on (1) asfollows [28]

SMR = RMRB minus (1198651 sdot 1198652 sdot 1198653) + 1198654 (1)

where the RMRB is computed according to Bieniawskirsquos [4]proposal F1 F2 and F3 are adjustment factors that are relatedto joints orientation with respect to slope orientation and F4is the correction factor depending on the excavation methodof slope

Table 1 shows the required parameters for determinationof RMRB and their rating for two walls of the Lashotor pass

Adjustment factors of F1 F2 and F3 for each probabilityslide plane or slide line are evaluated separately and theirresults are presented in Tables 2 and 3

Finally after determination of RMRB and adjustmentfactors for most critical state values of modified SMR for thetwo walls are calculated and presented in Table 4

The slope excavation method is a normal blastingThere-fore factor of F4 is zero

Shale unit

Limestone unit

Fresh rock surface Fault

Figure 3 A general view of the eastern slope rock unit fresh rocksurface and displacement of fault are shown

Table 2 Adjustment factors (1198651 1198652 and 1198653) of the western cutslope

1198651 1198652 1198653 1198651 sdot 1198652 sdot 1198653

J1 015 1 minus25 minus38J2 015 1 minus25 minus38J3 033 1 minus25 minus825J4 052 1 minus25 minus13Sliding line resultingintersection of J1 and J2 055 1 minus60 minus33

Bedding plane 06 015 minus60 minus54

The sumadjustment factors for thewedge failure aremorethan other types of failure Therefore it is concluded thatwedge failure type is more critical than others in both walls ofthe Lashotor pass and should be considered as a worst statewith lowest SMR rate

Based on the SMR classification system the rock massin the two slopes of the Lashotor pass is in the bad class(IV) and they are unstable and a big wedge failure is feasible(Probability of Failure 60)

32 Slope Stability Rating (SSR) Classification A lot of exca-vated slopes in Iran and Australia were studied by Taheri andTani [6] Based on this investigation they presented the slopestability rating (SSR) classification system as follows

SSR = GSI(2002) + (1198651 + 1198652 + 1198653 + 1198654 + 1198655) (2)


Previous failure

Unstable rock

(a)

Previous failure

Limestone unit

Shale unit

Kolah-Ghazi fault

(b)

Figure 4 Two views of the western slope rock unit Kolah-Ghazi fault branch unstable rock blocks and traces of previous slope failure areshown

Table 3 Adjustment factors (1198651 1198652 and 1198653) of the eastern cutslope

1198651 1198652 1198653 1198651 sdot 1198652 sdot 1198653



Table 4 SMR values

RMRB 1198651 sdot 1198652 sdot 1198653 + 1198654 SMRWestern cut slope 64 minus33 31Eastern cut slope 59 minus34 25

whereGSI(2002) ismodifiedGSI by Sonmez andUlusay (2002)and F1 F2 F3 F4 and F5 are adjustment factors whoseexplanation and rating are presented in Table 5

321 Determination of GSI(2002) To determine the GSI usingmodified chart of Sonmez and Ulusay [9] quantitative GSIchart two parameters of surface conditions rating (SCR) andstructural rating (SR) must be determined as follows

SCR = 119877119903 + 119877119908 + 119877119865 (3)

SR = minus175 ln (119869119881) + 798 (4)

where 119877119903 119877119908 and 119877119891 are roughness rating weatheringrating and infilling rating respectively and 119869119881 is the numberof joints per unit volume of rock mass Rating of theseparameters and the SCR value are presented in Table 6

The number of joints within unit volume of rock mass(119869119881) is calculated using the following equation

119869119881 =

119895

sum

119894=1

1

119878119894

(5)

Unstable wedge

Figure 5 The rock wedge prone to sliding in the west cut slope ofthe Lashotor pass

where 119878119894 is the average joint spacing inmeters for the 119894th jointset and 119895 is the total number of joint sets except the randomjoint set

In the studied slopes 119869119881 = 8 and SR value with use of (4)was equal to 43

Using two parameters SCR and SRGSI value of the slopesrock mass was determined to be about 55

322 Determination of Adjustment Factors 1198651 1198652 1198653 1198654and 1198655 F1 the intact rock strength UCS is one of theeffective parameters on the stability of rock slopes Point loadtest was done on approximately cubic shape samples Thepoint load index was determined to be about 42 and theuniaxial comparative strength of the samples were estimatedusing the point load index in the range of 50 to 100MpaTherefore the rate of F1 according to Table 5 is equal to 28

F2 slope stability analyses showed that the variation of119898119894in the Hoek-Brown failure criterion and the dry unit weightof intact rock have considerable effects on the stability ofrock slopes Since these two parameters are related to rocktype (lithology) of slope Taheri and Tani [6] with the use ofthe reference tables of rock material specifications proposedby Hoek et al [36] classified rocks into six groups withdifferent lithological characteristics (Table 6) As mentionedabove lithology of the rockmass of the slopes is carbonate andshale which according to Table 5 are in Group 3 and theirrates are equal to 9


7

N

S

EWBedding

J1

J2

J3

J4

Western Eastern

OrientationsID Dipdirection

1 791272 901533 802034 862445 160336 802307 78048

Equal anglelower hemisphere

253 poles

Figure 6 The stereographic projection of joints sets and bedding in the western and eastern slope of the Lashotor pass

(a) (b)

Figure 7 (a)Three-dimensional view of the sliding wedge which forms the intersection of the joints J1 and J2 and the western slope face (b)Three-dimensional view of the sliding wedge which forms the intersection of the joints J2 and J3 and the eastern slope face

Table 5 Adjustment factors 1198651 1198652 1198653 1198654 and 1198655 and range of value in the SSR classification system (Taheri and Tani 2010) [6]

Parameter Range of values

1198651

Uniaxial compressivestrength (MPa) 0ndash10 10ndash25 25ndash50 50ndash100 100ndash150 150ndash200

Rating 0 7 18 28 37 43

1198652

Rock type Group 1 Group 2 Group 3 Group 4 Group 5 Group 6Rating 0 4 9 17 20 25

1198653

Slope excavation method Waste damp Poor blasting Normal blasting Smooth blasting Presplitting Natural slopeRating minus11 minus4 0 6 10 24

1198654

Groundwater

(Groundwaterlevel from bottomof the slopeslopeheight) times 100

Dry 0ndash20 20ndash40 40ndash60 60ndash80 80ndash100

Rating 0 minus1 minus3 minus6 minus14 minus18

1198655

Earthquake force Horizontalacceleration 0 015 g 020 g 025 g 030 g 035 g



25

50

75

100

35 45 55 65 75 85

Hei

ght (

m)

SSR

30 45 50 55 60 65 704035

Slope angleFS = 1

Figure 8 Determination of stable dip of rock slope based on SSRvalue and slopersquos height

Table 6 Joints surface condition rating (SCR) and its rating in thestudied slopes according to modified GSI classification [9]

Roughness Weathering Infilling SCR(mean)

Description Rough-very rough None slightly Hard mdashRating 5-6 5-6 2ndash4 14

F3 the slope excavation method has considerable effectson the stability of rock slopes The conventional excavationmethods and their rates are presented in Table 5 As previ-ously mentioned excavation method of the Lashotor pass isnormal blasting and according to Table 5 1198653 = 0

F4 since the groundwater level is below the bottom of thepass rate of this parameter (F4) according to Table 5 is equalto zero

F5 the dynamic loading of earthquake has great effectson instability of slopes and should account for slope stabilityanalysis especially in active seismic zones Based on theseismic hazard zonation map of Iran for the return period of75 years [37] the Lashotor pass is located in the low risk zonewith the horizontal ground acceleration of about 02 g

In detailed study the amount of horizontal earthquakeacceleration for studied area can be calculated using therelationship between the distance of the site to the hypocenterof earthquakes and earthquakes magnitude

Also various relations are proposed by many researchersfor any regions to determine the magnitude of earthquakesin terms of the length of causative fault The most widelyused of these relations for Iran are presented by Mohajer-Ashjai and Nowroozi [31] Nowroozi [29] and Ambraseysand Melville [30] Major faults at the study area and otherrequired parameters to calculate the maximum earthquakemagnitude and horizontal peak ground acceleration (PGA)are presented in Table 7 The results of calculations of themaximum earthquake magnitude and PGA for the majorfaults around the Lashotor pass are presented in Table 8

Based on the results of the calculations the predictedmaximum ground horizontal acceleration for the study areais equal to 03 g which is generated by theDehagh fault (DeF)Therefore rate of F5 according to Table 5 is determined to beequal to minus22

323 Calculation of SSR and the Slope Stability AssessmentThe value of slope stability rating (SSR) of two walls of theLashotor pass was determined to be about 70 Due to the lackof orientation effect of discontinuities with respect to slope

orientation in SSR value the value of SSR is the same for bothsides of the Lashotor pass

Taheri and Tani [6] presented several graphs with thedifferent safety factor for judgments about slope stabilitybased on height and dip of the slope and its SSR value Byplotting of the SSR value versus the slopes height in thesegraphs (Figure 8) it was found that the dip of the studiedslopes (approximately 80∘) was higher than the maximumstable dips (nearly 65∘) Therefore to achieve stable slopeswith theminimum acceptable safety factors (FS = 1) the dipsangle of slopes should be reduced to less than 67∘

4 Rockfall Simulation AnalysisAn essential component in the evaluation of potential haz-ard of rock slope instability is simulation of rockfalls toestimate the rock falling trajectories translational velocitytotal kinetic energy and endpoints location of the fallingrocks RocFall software is a 2D statistical analysis programfor rockfall simulation In this paper RocFallDV4 software[38] was used for modeling of rockfalls in the Lashotor passRockfall simulation in the Lashotor pass in Figure 9 indicatedthat most of the falling rocks will reach the highway

As it is shown in Figure 10 falling rock have high velocitywhich exceeded 20ms in the moment of impact with thesurface of highway

5 Falling Rock HazardOne of the most accepted methods for rockfall hazard assess-ment in highway is the rockfall hazard rating system (RHRS)developed by Pierson et al [35] Table 9 gives includedparameters and typical scores in this classification systemAlso the scores of each parameter (119910) can be determined by119910 = 3

119909 where 119909 for different parameter is calculated by

Slope height

119909 =

slope height (feet)25

Average vehicle risk

119909 =

time25

Decision Sight distance ()

119909 =

(120 minusDecision sight distance)20

Roadway width

119909 =

(52 minus Roadway width (feet))8

Block size119909 = Block size (feet)

Volume

119909 =

Volume (cuft)3

(6)


0

10

20

30

0 5 10 15 20 25

Horizontal distance (m)

Hei

ght (

m)

minus25

minus20

minus15

minus10

minus5

(a)

0

2

4

6

8

10

5 13

Num

ber o

f ro

cks

Location (m)

Horizontal location of rock endpoints

minus18 minus10 minus3

(b)

Figure 9 (a) Slopes geometry and trajectories (b) Endpoints graph of falling rock fragments

Table 7 Major faults at around of the Lashotor pass

Name of fault Strikedip and dip direction of fault Length (km) Mechanism Horizontal distance (km)North Baharestan (NBF) 095ndash1156011989075 SW 45 D + R 67Baharestan (BF) 280ndash30045 NE 33 R + D 24Dalan (DaF) 290ndash32060 NE 180 R + D 51Mobarakeh (MoF) 310ndash32570 NE 60 R + D 21Dizicheh (DiF) 310ndash3357511989080 NE 37 R + D 19Dehaghan (DF) 120ndash14560 SW 250 R + D 56Dehagh (DeF) 290ndash3206011989070 NE 200 R + D 16Kolah-Ghazi (KGF) 300ndash31055 NE 50 R + D 0Foladshahr (FF) 120ndash14570 SW 70 R + D 11N normal R reverse D dextral and S sinistral strike-slip component of movements

0

5

10

15

20

25

30

0 10 20

Tran

slatio

nal v

eloci

ty (m

s)

Location (m)minus10minus20

Figure 10 Translational velocity envelope of rockfalls

(1) Slope height (m) vertical height of the slope hasgreat effect on the energy and velocity of filling rocksHeight of the Lashotor slopes is about 34 meters Oneof the factors which can be very hazardous rockfallevent in the Lashotor pass is the height of the slopes

(2) Ditch effectiveness the effectiveness of a ditch ismeasured by its ability to prevent falling rock fromreaching the roadway [39]As is shown in Figures 3 and 4 the highway hasno ditch Therefore the rating of this category wasassumed to be equal to 81

(3) Average vehicle risk (AVR) this parameter definedpercentage of time that a vehicle will be at risk andcalculated as [20]

AVR = (ADT24) times Slope lengthPosted speed limit

times 100 (7)

whereADT is the average traffic per day (vehicleday)Posted speed limit in this section of highway equals120 kmh and the slope length is about 250m Withrespect to importance of the Shiraz-Isfahan highwaythis highway has heavy traffic Therefore at most ofthe timemore than one vehicle is presentedwithin theLashotor pass (AVR gt 100)

(4) Percent of decision sight distance this parameter isdependent on two items (1) the length of roadwaythat drivers need to make instantaneous decisionwhich is function of posted speed limit through therockfall section and (2) actual sight distance that isdefined as shortest distance along a roadway that asix-inch object is continuously visible to a driverPercent of decision sight distance can be calculated asfollows [20]

DSD =Actual sight distancedecision sight distance

times 100 (8)


Table 8 Maximum potentiality earthquakes magnitude of faults and maximum horizontal acceleration in the study area

Fault Nowroozi[29]

Ambraseys andMelville [30]

Mohajer-Ashjaiand Nowroozi [31] Mean Dams and

Moore [32]Niazi and

Bozorgnia [33]Zare et al

[34] PGA

NBF 67 66 68 67 039 016 016 024BF 65 64 66 65 037 014 015 022DaF 73 73 73 73 024 013 008 015MoF 68 67 69 68 032 013 011 019DiF 66 64 67 657 029 011 01 017DF 73 73 73 73 026 015 007 014DeF 73 73 73 73 051 024 021 03KGF 67 66 68 67 041 016 018 025FF 69 68 69 687 041 017 017 025

Table 9 Rockfall hazard rating system parameters and their scores [35]

Category Rating criteria and scorePoints 3 Points 9 Points 27 Points 81

Slope height 75m 15m 225m 30mDitch effectiveness Good catchment Moderate catchment Limited catchment No catchmentAverage vehicle risk ( of time) 25 50 75 100

Percent of decision sightdistance

Adequate sight distance100 of low design value

Moderate sightdistance 80 of lowdesign value

Limited sight distance60 of low design value

Very limited sightdistance 40 of lowdesign value

Roadway width included pavedshoulders 1320m 1080m 840m 600m

Geologic characterCase 1

Structural condition Discontinuous jointsfavorable orientation

Discontinuous jointsrandom orientation

Discontinuous jointsadverse orientation

Continuous jointsadverse orientation

Rock friction Rough irregular Undulating Planar Clay infilling orslickenside

Case 2

Structural condition Few differential erosionfeatures

Occasional differentialerosion features

Many differentialerosion features

Major differentialerosion features

Difference in erosion rates Small Moderate Large ExtremeBlock size 3048 cm 6096 cm 9144 cm 12192 cmVolume of rockfall per event 23m3 46m3 69m3 92m3

Climate and presence of wateron slope

Low to moderateprecipitation no freezingperiods no water on slope

Moderate precipitationor short freezingperiods intermittentwater on slope

High precipitation orlong freezing periods orcontinual water onslope

High precipitation andlong freezing periods orcontinual water onslope and long freezingperiods

Rockfall history Few falls Occasional falls Many falls Constant falls

According to ODT [40] suggestion the lower valueof the decision sight distance in speed of 120 kmh isabout 340mThe route in the Lashotor pass is straightand no horizontal and vertical curves or obstaclesexist on the road that limit sight of deriversThereforeactual sight distance is approximately equal to neededdistance for deriver decision

(5) Roadway width this item defines the availablemaneuver room for a driver to avoid fallingfallen

rock blocks The roadway width of the Lashotor passwith respect to the highway is divided by centerlinebocks considering half whole of its width (measuredfrom one edge of the shoulders to the centerlinebocks)

(6) Geologic character the RHRS method discussedtwo categories of the geological conditions whichcontrol rockfalls Case 1 includes slopes or cuts wherejoints bedding planes or other discontinuities are


Table 10 RHRS ratings for the Lashotor slopes

Parameter Value RatingSlope height 34 100Ditch effectiveness No catchment 81Average vehicle risk 450 100Sight distance Adequate sit distance 100 3Roadway width 12m 6

Structural condition Continuous joints adverseorientation 81

Rock friction Planar 27Block size 05ndash1m 37Climate water Moderate precip 9Rockfall history Occasional falls 9Total score 461

the dominant structural feature that control rockfallsoccurrence In this case consider continuity andorientation of joints and rock friction Case 2 is forslopes where differential erosion andor oversteep-ened slopes are the main factors that control rockfallsoccurrence Field survey and study of rockfall eventthat occurred in the Lashotor slopes show that theslopes are classified as case 1 Orientation continuityand surface condition of 253 discontinuities in theLashotor slopes were defined

(7) Block size or volume of rockfall per event use of blocksize or volume depends on type of rockfall event thatis most likely to occur Block size should be usedfor individual block fall and volume should be usedfor rock mass fall Based on field survey individualblocks are typical of the rockfall in the Lashotor passalthough rock mass fall is not unexpected

(8) Climate and presence of water on slope presence ofwater and freezethaw cycles in addition to reducingthe rock mass stability also played important role inthe weathering [39] According to the meteorologicalrecords average of annual rainfalls in the studied areais about 122mm and average of minimum temper-ature in December January and February is belowzero

(9) Rockfall history historical information about fre-quency and magnitude of previous rockfall events isan excellent indicator for future expected events [20]Except for the huge failure that occurred during theconstruction period there is not any official reportabout rockfall occurrence in the Lashotor cut slopesBut the evidences of various rockfall events wereindicated in the felid survey

Summary explanation of RHRS parameters and ratings in theLashotor pass is presented in Table 10

According to this classification slopes with a total scoreless than 300 are assigned a very lowprioritywhile slopeswitha rating in excess of 500 are identified for urgent remedialaction As shown in Table 10 total score or RHRS value of

the Lashotor pass slopes is about 461 that is near to limit of500 and therefore remedial action is urgent

6 ConclusionField evidence and primary survey of the Lashotor passindicate high potentiality of slope failure in two of its rock cutslopes Joint study and analysis of results with use of Dips andSwedge software indicate high likelihood of wedge failureespecially in the eastern slope and toppling in the two slopesThe most significant influenced parameter in the Lashotorslopes instabilities is presence of the fault in the walls of thepass

Based on the SMR values of slopes the slopes rock massis in bad class and unstable and prone to big failure Basedon SSR values and with respect to dip and high of the slopessafety factors of both slopes are less than 1 and thereforeunstable

Also based on this interaction matrix and the weightingcoefficient of the parameters presented by KhaloKakaie andNaghadehi [26] instability indexes (IIj) of the Lashotor slopesare about 57 and classified as the unstable slopes

Rockfall simulation in the Lashotor pass by RocFallsoftware indicated that most of the falling rocks will reach thehighway Rockfall hazard rating system value of the Lashotorpass slopes is about 461 that emphasizes the risk of instabilityand the danger threatening vehicle moving there

Based on two rock mass classification systems SMRand SSR probability of slope instability occurrence in theLashotor pass is high and based on rockfall simulation androckfall hazard rating system occurrence of rockfall in theLashotor pass can have very dangerous resultsTherefore theLashotor should be classified as high-risk area

One of the considerable problems in the Lashotor pass isexposure of shale layers in south section Since the shale rockis weak and prone to weathering deterioration and softeningof the shale layer along the time increase the instabilitypotential of the slopes In addition to that long periods ofexposure of carbonate rock mass to the slope face allow forthe increase of weathering effects and weaken the rock masswhich result in increased possibility of dislodging of rockpieces

Studying various methods of stabilization of the slope(advantage limitation and applied requirement) and withrespect to the slopes conditions reinforced shotcrete is sug-gested for the slopes stabilization Shotcrete protects the rockfrom progressive weathering and erosions that could even-tually produce unstable overhangs and increased instabilitypotential The reinforced shotcrete will also control the fallof small blocks of rock and increase structural support Alsosimulation of rockfalls with RocFall V4 software indicatedthat dig of shallowditches in two sides of the highway can trapa large number of fallen rock fragments and prevents themfrom arriving to the highway

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper


References

[1] WW LowranceAcceptable Risk Science and the Determinationof Safety William Kaufmann Incorporated Los Altos CalifUSA 1976

[2] ISO ldquoRisk management vocabularyrdquo ISOIEC Guide 73 Inter-national Organization for Standardization Geneva Switzer-land 2002

[3] L Pantelidis ldquoRock slope stability assessment through rockmass classification systemsrdquo International Journal of RockMechanics andMining Sciences vol 46 no 2 pp 315ndash325 2009

[4] Z Bieniawski ldquoThe geomechanics classification in rock engi-neering applicationsrdquo in Proceedings of the 4th ISRM CongressMontreux Switzerland 1979

[5] M Romana ldquoNew adjustment ratings for application of Bieni-awski classification to slopesrdquo in Proceedings of the InternationalSymposium on Role of Rock Mechanics (ISRM rsquo85) ZacatecasMexico 1985

[6] A Taheri and K Tani ldquoAssessment of the stability of Rockslopes by the slope stability rating classification systemrdquo RockMechanics andRock Engineering vol 43 no 3 pp 321ndash333 2010

[7] A Taheri and K Tani ldquoRock slope design using Slope StabilityRating (SSR)Application andfield verificationsrdquo inProceedingsof the 1st Canada-US RockMechanics Symposium-RockMechan-ics Meeting Societyrsquos Challenges and Demands Two Volume Setpp 215ndash221 Taylor amp Francis May 2007

[8] H Sonmez and R Ulusay ldquoModifications to the geologicalstrength index (GSI) and their applicability to stability ofslopesrdquo International Journal of Rock Mechanics and MiningSciences vol 36 no 6 pp 743ndash760 1999

[9] H Sonmez and R Ulusay ldquoA discussion on the Hoek-Brownfailure criterion and suggested modifications to the criterionverified by slope stability case studiesrdquo Yerbilimleri no 26 pp77ndash99 2002

[10] R Hack ldquoAn evaluation of slope stability classificationrdquo inProceedings of the ISRM International Symposium on RockEngineering for Mountainous Regions (EUROCK rsquo02) 2002

[11] E Hoek and J Bray Rock Slope Engineering Taylor amp FrancisLondon UK 1981

[12] P Budetta ldquoAssessment of rockfall risk along roadsrdquo NaturalHazards and Earth System Science vol 4 no 1 pp 71ndash81 2004

[13] R Spang and T M Sonser ldquoOptimized rockfall protection bylsquoROCKFALLrsquordquo in Proceedings of the 8th ISRM Congress TokyoJapan 1995

[14] A Ritchie ldquoEvaluation of rockfall and its controlrdquo HighwayResearch Record 17 1963

[15] R Spang ldquoProtection against rockfall-stepchild in the design ofrock slopesrdquo in Proceedings of the 6th ISRM Congress 1987

[16] T J Pfeiffer and T D Bowen ldquoComputer simulation ofrockfallsrdquo Bulletin of the Association of Engineering Geologistsvol 26 no 1 pp 135ndash146 1989

[17] J Pfeiffer D Higgins and K Turner ldquoComputer aided rockfallhazard analysisrdquo in Proceedings of 6th International Associationof Engineering Geology Congress(IAEG rsquo90) pp 93ndash103 1990

[18] A Azzoni and M H De Freitas ldquoExperimentally gainedparameters decisive for rock fall analysisrdquo Rock Mechanics andRock Engineering vol 28 no 2 pp 111ndash124 1995

[19] W D Stevens RocFall a Tool for Probabilistic Analysis Designof Remedial Measures and Prediction of Rockfalls Department ofCivil Engineering Master of Applied Science Graduat Universityof Toronto Toronto Canada 1998

[20] L Pierson and R Van Vickle ldquoRockfall hazard rating systemparticipantrsquos manualrdquo Publication FHWA SA-93-0571993 Fed-eral Highway Administration Washington DC USA 1992

[21] L Pantelidis ldquoA critical review of highway slope instability riskassessment systemsrdquo Bulletin of Engineering Geology and theEnvironment vol 70 no 3 pp 395ndash400 2011

[22] F Guzzetti P Reichenbach and S Ghigi ldquoRockfall hazard andrisk assessment along a transportation corridor in the Neravalley central Italyrdquo Environmental Management vol 34 no 2pp 191ndash208 2004

[23] ANadimi andA Konon ldquoStrike-slip faulting in the central partof the Sanandaj-Sirjan Zone Zagros Orogen Iranrdquo Journal ofStructural Geology vol 40 no 1 pp 2ndash16 2012

[24] M-A Brideau M Yan and D Stead ldquoThe role of tectonicdamage and brittle rock fracture in the development of largerock slope failuresrdquo Geomorphology vol 103 no 1 pp 30ndash492009

[25] H R Pourghasemi B Pradhan andC Gokceoglu ldquoApplicationof fuzzy logic and analytical hierarchy process (AHP) to land-slide susceptibility mapping at Haraz watershed Iranrdquo NaturalHazards vol 63 no 2 pp 965ndash996 2012

[26] R KhaloKakaie and M Z Naghadehi ldquoThe assessment of rockslope instability along the Khosh-Yeylagh Main Road (Iran)using a systems approachrdquo Environmental Earth Sciences vol67 no 3 pp 665ndash682 2012

[27] A Ghazifard and A Movahedzadeh ldquoCauses of landslides inthe newly built road Isfahan-Shirazrdquo in Proceedings of the 1stConfiguration Engineering Geology amp Environment pp 221ndash215Tehran Iran 2000

[28] B Singh and R K Goel Rock Mass Classification A PracticalApproach in Civil Engineering vol 46 Elsevier New York NYUSA 1999

[29] A A Nowroozi ldquoEmpirical relations between magnitudesand fault parameters for earthquakes in Iranrdquo Bulletin of theSeismological Society of America vol 75 no 5 pp 1327ndash13381985

[30] N N Ambraseys and C P Melville A History of PersianEarthquakes Cambridge University Press Cambridge UK2005

[31] A Mohajer-Ashjai and A A Nowroozi ldquoObserved and proba-ble intensity zoning of Iranrdquo Tectonophysics vol 49 no 3-4 pp149ndash160 1978

[32] Dames amp Moore International SRL Report Seismic StudiesInvestigation of Surface Faulting Proposed Medical CenterDames amp Moore International Tehran Iran 1975

[33] M Niazi and Y Bozorgnia ldquoBehavior of near-source peakhorizontal and vertical ground motions over SMART-1 arrayTaiwanrdquo Bulletin of the Seismological Society of America vol 81no 3 pp 715ndash732 1991

[34] M Zare M Ghafory-Ashtiany and P Bard ldquoAttenuation lawfor the strong motions in Iranrdquo in Proceedings of the 3rd Inter-national Conference on Seismology and Earthquake EngineeringSEE-3 pp 345ndash355 Tehran Iran 1999

[35] L A Pierson S A Davis and R Van Vickle ldquoRockfall Hazardrating system implementation manualrdquo Number FHWA-OR-EG-90-01 1990

[36] E Hoek C Carranza-Torres and B Corkum ldquoHoek-Brownfailure criterion-2002 editionrdquo in Proceedings of 5th NorthAmerican Rock Mechanics Symposium and 17th Tunneling Asso-ciation of Canada Conference (NARMS-TAC rsquo02) pp 267ndash2732002


[37] IIEES ldquoseismic hazard zonation map of Iran for the returnperiod of 75 yearsrdquo Tehran 2005 httpwwwiieesacir

[38] RocscienceRocFall V4 A Statistical Analysis ProgramDesignedto Assist with a Risk Assessment of Slopes at Risk of RockfallsRocscience Ontario Canada 2004

[39] D C Wyllie and C Mah Rock Slope Engineering Taylor ampFrancis London UK 2004

[40] ODT ldquoStopping sight distance and decision sight distancerdquoDiscussion Paper 8A Oregon by The Kiewit Center for Infras-tructure andTransportationOregon StateUniversity CorvallisOre USA 2004

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of


EarthquakesJournal of


Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining


Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of


Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering


GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of


OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in


MineralogyInternational Journal of


MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Geological ResearchJournal of


Geology Advances in


drilling procedure [3] Furthermore in the RMR and SMRclassification systems are simultaneously used the RQD indexand ldquodiscontinuity spacingrdquo parameter In fact the spacingof discontinuities has double influence on the final rating[10] The other advantage of SSR classification is takeninto account the effect of earthquake force on the slopeinstability This is very important and essential for slopesstability analyses in seismic active zones Iran is located in theAlpine-Himalayan orogenic system and shows high seismicactivity

In many cases spatially in vertical slopes or very steepslopes such as cut slope other types of rock slope failure(wedge failure planer failure and toppling) may eventuallylead to the rockfall event If sliding distance of rock block orrock mass that detached by sliding toppling or falling wasnegligible to descending distance through air it is defined asa rockfall [11] Rockfalls constitute amajor hazard in rock cutsalongside roads inmountainous regions that causes loss of lifeand property because of its very rapid movement [12]

In the past the rockfall simulation was based on experi-ence and extensive in situ rockfall tests [13] Ritchie [14] bycarrying out full scale tests on rockfall event proposed simplechart for determining required width and depth of rock catchditches in relation to height and slope angle Over the lastdecades many computer programs are developed for simula-tion of rockfall [15ndash18] One of themost practical programs ofthese computer programs is the RocFall software that can beused to simulate almost all types of rockfall events [19] Thissoftware provides valuable information about kinetic energyvelocity bounce height and fall-out distance of falling rockfragment that are essential to determine the consequence anddegree of danger of slope instability The RocFall softwarealso can be used to design remedial measures and test theireffectiveness [19]

At the last two decades a number of slope instabilityrisk assessment systems have been developed and rockfallhazard rating system [20] is one of the most well-knownof these systems [21] This method used a simple approachfor assessing and quantifying the risk of rockfalls in thetransportation routes [22] The rockfall hazard rating system(RHRS) contains nine deferent parameters which can bedivided into two groups the parameters that define rockfallhazard (slope height geologic character volume of rock-fallblock size climate and presence of water on slope androckfall history) and the parameters that indicate the vehiclevulnerability (ditch effectiveness average vehicle risk percentof decision sight distance and roadway width) [12]

In this research at the first step the instability potentialof the Lashotor trenches was assessed by use of SMR andSSR classification systems Rock mass classifications indicatehigh instability potential and likely rockfalls in the Lashotorcut slopes Therefore direction speed and energy of thefalling rock fragments are simulated for risk analyses usingthe RocFall software Finally the risk of falling rocks for thevehicles passing the Lashotor pass is estimated by using therockfall hazard rating system

2 General Characteristics of the Study Area

The Lashotor pass was constructed at 1991 in distance of22 km of the Isfahan-Shiraz highway in Iran to eliminate theinappropriate and dangerous curvatures in the Lashotor passand shorten the path As shown in Figure 1 the length ofthe previous way is 688 km while the current path in theLashotor pass is 362 km Also the new road is straighter thanthe previous one Generally this pass has 250 meters lengthand 24 meters width The maximum height of the walls is 34meters and the dips of the cut slopes are about 80 degrees

Geologically the Lashotor pass is located in the Kolah-Ghazi region in the central part of the Sanandaj-Sirjan zoneIn this region 30 to 50 meters of the upper Cretaceouslimestone is lying on the lower Cretaceous shale and marllayers In the central part of the Sanandaj-Sirjan zone thefault pattern consists of major NW-trending longitudinalfaults NE-SW-trending transverse faults and N-S-trendingoblique faults [23] Fault pattern in the study area is shown inFigure 2

The nearest fault to the Lashotor pass is the Kolah-Ghazi fault This fault has several branch minor faultsApproximately 61m offset occurs along the Kolah-Ghazifault where the Quaternary gravel plains and the Holocenealluvial deposits are dissected and dextrally displaced by thefault and its branching minor faults The maximum valueof the slip rate calculated along the Kolah-Ghazi fault isabout 92mmyear [23] Figures 3 and 4 show general view ofthe eastern and western Lashotor cut slopes The movementcaused by fault in the eastern cut slope face is indicated inFigure 3 Figure 4 shows a branch fault of the Kolah-Ghazifault in the southern part of the Lashotor pass

The presence of tectonic structures such as faults andfolds can play significant role in the slope instability [24]According to Pourghasemi et al [25] there is high instabilityprobability of slopes in distance less than 100m of faultsKhaloKakaie and Naghadehi [26] studied slope stability withuse of interaction matrix and estimated proportional shareof sixteen parameters in slope failure According to thesestudies presence of faults and folds played significant role inthe slope failure and its proportional share in slope failure isabout 775

Figure 4 shows an unstable rock wedge in the westernslope that is formed by intersection of the joint sets Theseare just a few of evidences which address the instability of cutslopes in the Lashotor pass The most notable failure in thispass occurred during a constructionwhich caused temporarycessation of excavation [27] The failed part of the westernslope is shown in Figure 5

3 Assessment of Instability Potential andFailure Types of the Slopes

For assessing of instability potential and failure types at thefirst step discontinuity and their spatial orientations in theLashotor slopes were studied According to the strike and dipof the discontinuity in respect to slope face orientation we


N



362km

3km

688 km

N32∘27

99840012

998400998400

N32∘27

99840012

998400998400

51∘45

99840023

998400998400E 51∘45

99840023

998400998400E










Isfahan

Study areaNajafabad

Falavarjan

Foladshahr

Tiran

Zefreh

Yankabad

Borujen

ZarinshahrMobarakeh

Shahreza

MoF

Dehaghan





Dif

FFKolah Ghazi fault


BF3BF1

NBFBF2

Ramsheh fault


Dehagh fault

Murche Khurt faultN









Shale unit

Limestone unit




1198651 1198652 1198653 1198651 sdot 1198652 sdot 1198653






SSR = GSI(2002) + (1198651 + 1198652 + 1198653 + 1198654 + 1198655) (2)


Previous failure

Unstable rock

(a)

Previous failure

Limestone unit

Shale unit

Kolah-Ghazi fault

(b)



1198651 1198652 1198653 1198651 sdot 1198652 sdot 1198653



Table 4 SMR values




SCR = 119877119903 + 119877119908 + 119877119865 (3)

SR = minus175 ln (119869119881) + 798 (4)



119869119881 =

119895

sum

119894=1

1

119878119894

(5)

Unstable wedge








7

N

S

EWBedding

J1

J2

J3

J4

Western Eastern


1 791272 901533 802034 862445 160336 802307 78048


253 poles


(a) (b)




1198651


Rating 0 7 18 28 37 43

1198652


1198653


1198654

Groundwater




1198655




25

50

75

100

35 45 55 65 75 85

Hei

ght (

m)

SSR

30 45 50 55 60 65 704035

Slope angleFS = 1


















Slope height

119909 =



119909 =

time25


119909 =


Roadway width

119909 =



Volume

119909 =

Volume (cuft)3

(6)


0

10

20

30

0 5 10 15 20 25


Hei

ght (

m)

minus25

minus20

minus15

minus10

minus5

(a)

0

2

4

6

8

10

5 13

Num

ber o

f ro

cks

Location (m)



(b)




0

5

10

15

20

25

30

0 10 20

Tran

slatio

nal v

eloci

ty (m

s)







times 100 (7)




times 100 (8)



Fault Nowroozi[29]



Moore [32]Niazi and


[34] PGA

















Case 2






































References



















































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


N



362km

3km

688 km

N32∘27

99840012

998400998400

N32∘27

99840012

998400998400

51∘45

99840023

998400998400E 51∘45

99840023

998400998400E










Isfahan

Study areaNajafabad

Falavarjan

Foladshahr

Tiran

Zefreh

Yankabad

Borujen

ZarinshahrMobarakeh

Shahreza

MoF

Dehaghan





Dif

FFKolah Ghazi fault


BF3BF1

NBFBF2

Ramsheh fault


Dehagh fault

Murche Khurt faultN









Shale unit

Limestone unit




1198651 1198652 1198653 1198651 sdot 1198652 sdot 1198653






SSR = GSI(2002) + (1198651 + 1198652 + 1198653 + 1198654 + 1198655) (2)


Previous failure

Unstable rock

(a)

Previous failure

Limestone unit

Shale unit

Kolah-Ghazi fault

(b)



1198651 1198652 1198653 1198651 sdot 1198652 sdot 1198653



Table 4 SMR values




SCR = 119877119903 + 119877119908 + 119877119865 (3)

SR = minus175 ln (119869119881) + 798 (4)



119869119881 =

119895

sum

119894=1

1

119878119894

(5)

Unstable wedge








7

N

S

EWBedding

J1

J2

J3

J4

Western Eastern


1 791272 901533 802034 862445 160336 802307 78048


253 poles


(a) (b)




1198651


Rating 0 7 18 28 37 43

1198652


1198653


1198654

Groundwater




1198655




25

50

75

100

35 45 55 65 75 85

Hei

ght (

m)

SSR

30 45 50 55 60 65 704035

Slope angleFS = 1


















Slope height

119909 =



119909 =

time25


119909 =


Roadway width

119909 =



Volume

119909 =

Volume (cuft)3

(6)


0

10

20

30

0 5 10 15 20 25


Hei

ght (

m)

minus25

minus20

minus15

minus10

minus5

(a)

0

2

4

6

8

10

5 13

Num

ber o

f ro

cks

Location (m)



(b)




0

5

10

15

20

25

30

0 10 20

Tran

slatio

nal v

eloci

ty (m

s)







times 100 (7)




times 100 (8)



Fault Nowroozi[29]



Moore [32]Niazi and


[34] PGA

















Case 2






































References



















































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in





Isfahan

Study areaNajafabad

Falavarjan

Foladshahr

Tiran

Zefreh

Yankabad

Borujen

ZarinshahrMobarakeh

Shahreza

MoF

Dehaghan





Dif

FFKolah Ghazi fault


BF3BF1

NBFBF2

Ramsheh fault


Dehagh fault

Murche Khurt faultN









Shale unit

Limestone unit




1198651 1198652 1198653 1198651 sdot 1198652 sdot 1198653






SSR = GSI(2002) + (1198651 + 1198652 + 1198653 + 1198654 + 1198655) (2)


Previous failure

Unstable rock

(a)

Previous failure

Limestone unit

Shale unit

Kolah-Ghazi fault

(b)



1198651 1198652 1198653 1198651 sdot 1198652 sdot 1198653



Table 4 SMR values




SCR = 119877119903 + 119877119908 + 119877119865 (3)

SR = minus175 ln (119869119881) + 798 (4)



119869119881 =

119895

sum

119894=1

1

119878119894

(5)

Unstable wedge








7

N

S

EWBedding

J1

J2

J3

J4

Western Eastern


1 791272 901533 802034 862445 160336 802307 78048


253 poles


(a) (b)




1198651


Rating 0 7 18 28 37 43

1198652


1198653


1198654

Groundwater




1198655




25

50

75

100

35 45 55 65 75 85

Hei

ght (

m)

SSR

30 45 50 55 60 65 704035

Slope angleFS = 1


















Slope height

119909 =



119909 =

time25


119909 =


Roadway width

119909 =



Volume

119909 =

Volume (cuft)3

(6)


0

10

20

30

0 5 10 15 20 25


Hei

ght (

m)

minus25

minus20

minus15

minus10

minus5

(a)

0

2

4

6

8

10

5 13

Num

ber o

f ro

cks

Location (m)



(b)




0

5

10

15

20

25

30

0 10 20

Tran

slatio

nal v

eloci

ty (m

s)







times 100 (7)




times 100 (8)



Fault Nowroozi[29]



Moore [32]Niazi and


[34] PGA

















Case 2






































References



















































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


Previous failure

Unstable rock

(a)

Previous failure

Limestone unit

Shale unit

Kolah-Ghazi fault

(b)



1198651 1198652 1198653 1198651 sdot 1198652 sdot 1198653



Table 4 SMR values




SCR = 119877119903 + 119877119908 + 119877119865 (3)

SR = minus175 ln (119869119881) + 798 (4)



119869119881 =

119895

sum

119894=1

1

119878119894

(5)

Unstable wedge








7

N

S

EWBedding

J1

J2

J3

J4

Western Eastern


1 791272 901533 802034 862445 160336 802307 78048


253 poles


(a) (b)




1198651


Rating 0 7 18 28 37 43

1198652


1198653


1198654

Groundwater




1198655




25

50

75

100

35 45 55 65 75 85

Hei

ght (

m)

SSR

30 45 50 55 60 65 704035

Slope angleFS = 1


















Slope height

119909 =



119909 =

time25


119909 =


Roadway width

119909 =



Volume

119909 =

Volume (cuft)3

(6)


0

10

20

30

0 5 10 15 20 25


Hei

ght (

m)

minus25

minus20

minus15

minus10

minus5

(a)

0

2

4

6

8

10

5 13

Num

ber o

f ro

cks

Location (m)



(b)




0

5

10

15

20

25

30

0 10 20

Tran

slatio

nal v

eloci

ty (m

s)







times 100 (7)




times 100 (8)



Fault Nowroozi[29]



Moore [32]Niazi and


[34] PGA

















Case 2






































References



















































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


7

N

S

EWBedding

J1

J2

J3

J4

Western Eastern


1 791272 901533 802034 862445 160336 802307 78048


253 poles


(a) (b)




1198651


Rating 0 7 18 28 37 43

1198652


1198653


1198654

Groundwater




1198655




25

50

75

100

35 45 55 65 75 85

Hei

ght (

m)

SSR

30 45 50 55 60 65 704035

Slope angleFS = 1


















Slope height

119909 =



119909 =

time25


119909 =


Roadway width

119909 =



Volume

119909 =

Volume (cuft)3

(6)


0

10

20

30

0 5 10 15 20 25


Hei

ght (

m)

minus25

minus20

minus15

minus10

minus5

(a)

0

2

4

6

8

10

5 13

Num

ber o

f ro

cks

Location (m)



(b)




0

5

10

15

20

25

30

0 10 20

Tran

slatio

nal v

eloci

ty (m

s)







times 100 (7)




times 100 (8)



Fault Nowroozi[29]



Moore [32]Niazi and


[34] PGA

















Case 2






































References



















































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


25

50

75

100

35 45 55 65 75 85

Hei

ght (

m)

SSR

30 45 50 55 60 65 704035

Slope angleFS = 1


















Slope height

119909 =



119909 =

time25


119909 =


Roadway width

119909 =



Volume

119909 =

Volume (cuft)3

(6)


0

10

20

30

0 5 10 15 20 25


Hei

ght (

m)

minus25

minus20

minus15

minus10

minus5

(a)

0

2

4

6

8

10

5 13

Num

ber o

f ro

cks

Location (m)



(b)




0

5

10

15

20

25

30

0 10 20

Tran

slatio

nal v

eloci

ty (m

s)







times 100 (7)




times 100 (8)



Fault Nowroozi[29]



Moore [32]Niazi and


[34] PGA

















Case 2






































References



















































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


0

10

20

30

0 5 10 15 20 25


Hei

ght (

m)

minus25

minus20

minus15

minus10

minus5

(a)

0

2

4

6

8

10

5 13

Num

ber o

f ro

cks

Location (m)



(b)




0

5

10

15

20

25

30

0 10 20

Tran

slatio

nal v

eloci

ty (m

s)







times 100 (7)




times 100 (8)



Fault Nowroozi[29]



Moore [32]Niazi and


[34] PGA

















Case 2






































References



















































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in



Fault Nowroozi[29]



Moore [32]Niazi and


[34] PGA

















Case 2






































References



















































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in























References



















































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


References



















































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in















Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in










Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in

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Research Article Assessment of Slope Instability and …downloads.hindawi.com/journals/jgr/2014/763598.pdf · Research Article Assessment of Slope Instability and Risk Analysis of