Comparison between qualitative and quantitative rockfall risk methods for a hazardous road stretch

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ADVANCES in ENVIRONMENTAL and

AGRICULTURAL SCIENCE

Proceedings of the 4th International Conference on Energy Systems,

Environment, Entrepreneurship and Innovation (ICESEEI '15)

Proceedings of the 4th International Conference on Agricultural Science,

Biotechnology, Food and Animal Science (ABIFA '15)

Dubai, United Arab Emirates

February 22-24, 2015

Scientific Sponsor

University of Naples Federico II, Italy

Energy, Environmental and Structural Engineering Series | 32

ISSN: 2227-4359

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ADVANCES in ENVIRONMENTAL and

AGRICULTURAL SCIENCE

Proceedings of the 4th International Conference on Energy Systems,

Environment, Entrepreneurship and Innovation (ICESEEI '15)

Proceedings of the 4th International Conference on Agricultural Science,

Biotechnology, Food and Animal Science (ABIFA '15)

Dubai, United Arab Emirates

February 22-24, 2015

Published by WSEAS Press

www.wseas.org

All the copyright of the present book belongs to the World Scientific and Engineering Academy and Society Press. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the Editor of World Scientific and Engineering Academy and Society Press.

All papers of the present volume were peer reviewed by no less that two independent reviewers. Acceptance was granted when both reviewers' recommendations were positive.

ISSN: 2227-4359

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ADVANCES in ENVIRONMENTAL and

AGRICULTURAL SCIENCE

Proceedings of the 4th International Conference on Energy Systems,

Environment, Entrepreneurship and Innovation (ICESEEI '15)

Proceedings of the 4th International Conference on Agricultural Science,

Biotechnology, Food and Animal Science (ABIFA '15)

Dubai, United Arab Emirates

February 22-24, 2015

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Editors:

Prof. Nikos E. Mastorakis, Technical University of Sofia, Bulgaria

Committee Members-Reviewers: Vitale Cardone Leonardo Cascini Domenico Guida Joseph Quartieri Stefano Riemma Gianfranco Rizzo Mario Vento P. Pardalos

Eduardo Mario Dias Germano Lambert-Torres Zhuo Li Pradip Majumdar Shuliang Li Frangiskos V. Topalis Jan Awrejcewicz Vincenzo Niola Fotios Rigas Myriam Lazard Jiri Klima S. Sohrab Goricanec Darko Ze Santos Ehab Bayoumi Luis Tavares Rua Igor Kuzle Nikolay Djagarov Darko Goricanec

Maria do Rosario Alves Calado Gheorghe-Daniel Andreescu Patricia Jota Bharat Doshi Gang Yao Lu Peng Pavel Loskot Aida Bulucea F. Akgun Y. Baudoin M. Dasenakis G. E. Froudakis R. S. R. Gorla M. Heiermann C. Helmis I. Kazachkov A. M. A. Kazim G. Kiriakidis D. Kotzias A. Kurbatskiy S. Linderoth P. Lunghi J. Van Mierlo S. Ozdogan I. Poulios F. Rigas A. Stamou A. I. Zouboulis Z. A. Vale Claudio Guarnaccia Charles A. Long Tuan Pham Peter Dieter Andrei Korobeinikov Wolfgang Wenzel Seiji Shibasaki Gary A. Lorigan Ziad Fajloun Nikolai N. Modyanov Dhavendra Kumar Geoffrey Arden Photios Anninos W. Lakin

Lucio Tommaso De Paolis Jean-Michel Jault Hassane Oudadesse Anita H. Corbett Toshiharu Horie Vadim V. Sumbayev Andre Surguchov Rona R. Ramsay Daniel Martins-de-Souza Roberta Chiaraluce George Perry Gertz I. Likhtenshtein Vivo Turk Makoto Komiyama Shunsuke Meshitsuka Bahar Razavi Carlos E. Formigoni Corina Carranca Dragoi Andreea Lucija Foglar

Maria Leonor Da Silva Carvalho Rusu Teodor

Saber Abd-Allah Sadia Iqbal Ana Pilipovic

Anna Maria Pellegrino Arvind Dhingra Ayca Tokuc

Chi,Chieh-Tsung Bruce

Denizar Cruz Martins Denizar Martins Fahmy Bendary

Farhan Abdul Rauf George Culea Grabara Janusz

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Heimo Walter Ioana Adrian

Jose Manuel Mesa Fernández Marta Starostka-Patyk Mojtaba Ashouri Muslum Arici Nelson Duarte Oguz Arslan Paula Bajdor Rishabh Raj Thomas Panagopoulos Zeljko Tomsic

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Authors Index

Abdelhamid, M. 286 Deshmukh, S. 346 Khalifa, E. Z. 101

Abdi, A. L. 332 Di, G. 54 Khan, S. A. 382

Abdullah, W. G. 332, 400 Dirgantoro, M. A. 400 Khedaywi, T. 395

Ablaeva, A. 135 Dursun, M. 77 Khodadadi, A. 189

Abojassim, A. A. 354 El Sanabary, Z. 249 Kimsan, M. 373

Ahmed, E. A. 121, 313 Eleschova, Z. 73 Knebel, J. 36

Ajiboye, A. 169 El-Gammal, N. A. 101 Kontogianni, A. 96

Aksöz, A. 77 Ely-Kafrawy, A. A. 101 Korotkov, A. 363

Alboainain, S. 144 Falayi, T. 229, 241 Križan, P. 278

Alekseev, G. 271 Fernández Carrasco, P. 236 Kuasa, W. 400

Al-Gazaly, H. H. 354 Fray, D. J. 60 Kumar, A. 265

Amer, G. A. 101 Frolov, V. 363 Kumar, S. 382

Aro, S. O. 169 Ghazawi, Z. 395 La Zulfikar, Z. 332

Badr, I. A. 249 Giannini, E. N. 33 Labeeb, N. S. 249

Baka, W. K. 332 Giralda, V. M. 236 Leinartas, K. 60

Bastidas-Oyanedel, J.-R. 144 Giulia, M. 54 Liska, M. 73, 139

Beláň, A. 139, 224, 322 Glok, N. 271 Liska, M. 224, 322

Belasri, D. 144 Gouneem, A. 395 Liu, D. 408

Beniak, J. 278 Guida, M. 354 Liu, G. 408

Budetta, P. 13 Gupta, N. 382 Mabasa, C. 229

Cagno, E. 327 Hamdy, A. 249 Majahar Ali, M. K. 86

Cahyono, E. 332, 373, 400 Hammud, H. 154 Malav, L. C. 382

Carcadea, E. 127 Hamza, S. 286 Malav, M. K. 382

Carlino, S. 54 Haq, H. M. K. U. 45 Mansour, N. 286

Cattaneo, T. 111 Hiltunen, E. 45 Marinoiu, A. 127

Chairote, E. O. 377 Husain, Z. 265 Maroulis, Z. 33

Chairote, G. 377 Iqbal, S. 368 Martinkauppi, B. 45

Chen, Z. 408 Irwanto, D. 162 Mastorakis, N. E. 179, 255

Cobzaru, C. 127 Iswandi, R. M. 332 Mastorakis, N. E. 304, 368 Coxon, P. R. 60 Ivanic, M. 73, 224, 322 Matreninskiy, S. I. 18

Cruceanu, C. 214 Janicek, F. 139 Matúš, M. 278

Darabi, H. 189 Janiga, P. 73, 224, 322 Menéndez, E. P. 236

Darban, A. K. 189 Jarad, A. 340 Miečinskas, P. 60

De Lotto, R. 111 Juzeliunas, E. 60 Miloradov, M. 64

De Natale, G. 54 Kadhim, S. H. 354 Mischenko, V. Y. 18

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Moropoulou, A. 33 Rianse, I. S. 332 Suud, Z. 162

Mossa, A. M. 249 Rianse, U. 332, 400 Suzuki, M. 162

Mostafa, M. H. 294 Ruslan, M. H. 86 Taridala, S. A. A. 332

Muhidin 400 Sa, A. 327 Taweekasemsombat, S. 377

Naci Onus, A. 149 Saito, M. 162 Thollander, P. 327

Nalefo, L. 400 Salama, B. 294 Torres Delenne, P. R. 194

Nappi, M. 13 Sandulyak, Al. 135 Tourkolias, C. 96

Nathwani, J. 36 Sandulyak, An. 135 Troiano, A. 54

Nsair, E. 154 Sandulyak, D. 135 Troise, C. 54

Ntuli, F. 229, 241 Saygin, A. 77 Ulukapi, K. 149

Okonta, F. N. 241 Schmidt, J. E. 144 Varlam, M. 127

Opricovic, S. 64 Selim, M. E. 101 Venco, E. M. 111

Ornam, K. 373 Shaverdi, M. R. 189 Viglas, D. 139

Owolabi, O. A. 24 Sheweita, S. A. 294 Vojinovic-Miloradov, M. 64

Özdemir, B. 149 Singh, S. K. 265 Volčko, V. 224, 322

Park, S.-U. 204 Siouti, G. 33 Wang, F. 408

Pereverzev, V. A. 179, 255, 304 Skourtos, M. 96 Welcome, M. O. 179, 255, 304 Pereverzeva, E. V. 179, 255, 304 Skrypchuk, P. 81 Widayati, W. 332, 400

Permana, S. 162 Smirnov, A. 271 Yasir, S. M. 86

Raceanu, M. 127 Somma, R. 54 Zavala, M. A. 194

Razvodovsky, Y. E. 179, 255, 304 Šooš, L. 278

Reynoso Cuevas, L. 194 Sulaiman, J. 86

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Comparison between qualitative and quantitative rockfall risk methods

for a hazardous road stretch

PAOLO BUDETTA, MICHELE NAPPI

Department of Civil, Architectural and Environmental Engineering

University of Naples “Federico II”

Piazzale Tecchio, 80 – 80125 Naples

ITALY

paolo.budetta@unina.it

michele.nappi@unina.it

Abstract: - In order to compare rockfall risk values characterizing road sections affected by several rockfalls,

two procedures have been used: the modified Colorado Rockfall Hazard Rating System (mCRHRS) and the ROckfall risk MAnagement (RO.MA.) method. The first one is a qualitative method mainly based on a heuristic assessment and the second is a quantitative approach taking into account the occurrence probability of severe negative events. Even though the qualitative approach is not consistent with the definition of risk used in the quantitative procedure, we proved that mCRHRS ratings are comparable with risk values, expressed as probability of death of at least one occupant of a vehicle (fatal accident) exposed to the rockfall hazard per year.

Key-Words: - rockfall hazard, rockfall risk, quantitative risk analysis, roads, Sorrentine peninsula, southern

Italy

1 Introduction

Transportation corridors in a great deal of regions are often liable to undergo rockfalls, which cause a major risk for motorists as well as a large amount of damage and injuries. Over the last two decades, several qualitative and quantitative procedures have been proposed in order to evaluate the risk and reduce the potential consequences of rockfalls on the roads.

Generally, qualitative methods use exponential scoring patterns, and the total score reflecting the risk derives from the summation of scores of factors of different categories, such as: the slope height, ditch effectiveness, traffic, geological characteristics, failure magnitude and consequence [1], [2].

In quantitative approaches, the exposure to risk is given by the annual probability of rockfall failure, the vehicle being spatially and temporally in the path of the event when it occurs, and one or more occupants of the vehicle being killed as a result [3]. The quantitative risk assessment is an essential tool for planning risk mitigation measures [4]. It is important to note that qualitative approaches are not consistent with the definition of risk used in quantitative procedures (risk = hazard × consequences), and related results can be only qualitatively compared [5], [6].

The aim of this paper is to show results obtained applying, to the some road sections, two methods:

the modified Colorado Rockfall Hazard Rating System (mCRHRS) [7] and the ROckfall risk MAnagement (RO.MA.) approach [8]. The studied road sections belong to an important road linking some famous tourist resorts in the southern slope of the Sorrento Peninsula (southern Italy) such as Positano, Amalfi and Salerno, the province capital town. This road is affected by high traffic intensity because it is the only transportation corridor in this area that, due to its complex geomorphological and geo-structural setting, is sometimes affected by severe rockfalls, which cause injuries, damages and road closures.

2 The studied road

The road portion studied belongs to a very tortuous road path (Fig. 1) going along the coast (the Amalfitana state road) that was built in the middle of the 19th century by the Bourbon Department of Bridges and Roads. As a result of its age and impossibility of a modern realignment (in order to preserve the environmental heritage of this area protected by UNESCO), the road is characterized by only one single lane going in each direction without an adequate hard shoulder, and a high degree of road curvature. The width of the road is 7.0 m, but it is not wide enough in most places to allow vehicles to overtake one another (especially buses and

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F t k l t a b v t o g b i o c s 2 n t m d l r t n p i i r

3 e

T h S s Fig. 1 – Location trucks). The km/h. The studi length and cr territory, wa affected, in t been subdiv varying betw to have – as over the r geological ch Protection barriers, rein installed by owns the roa cuts belongin An analy spring/summ 2003, and fo night), allow traffic is ma motorcycles due to comm low season) replaced by the traffic is number of th per day, amo in the two dir in following road crossing

3 Geologi

events

The road cr high reliefs ly Salerno. By steep slopes,

of the study area imposed sp ied road str rossing the C as chosen be time, by roc vided into t ween about 22 s much as po road charac haracteristics n devices nforced wire ANAS (the ad), are pres ng to the stud ysis of traf mer and the

or different su wed to ascert ade up of c and tourist c muting and b during the an equally i s mainly ma hese vehicles ounting to 1,0 rections (tow calculations g foot-traffic

ical sett

rosses a coa ying on the n means of s , in a few d . eed limit is retch, of ab Conca dei M ecause it is ckfall events ten sections 25 and 380 m ossible – slo cterized by s (Table 1). constituted rope nets an e national c sent along so died road sec ffic data re autumn/win unlight cond tain that abo cars and the coaches. The usiness (very e spring/sum intense touri ade up of ca s (Nv) travell 058 in all ro wards Positan s was taken. is negligible

ting and

astal area ch northern side sub-vertical distance from everywhere out 3.0 km Marini munici the one m s. The road h , with leng m, defined so opes impend homogeneo by rock nd mesh drap ompany wh ome slopes a ctions. ecorded in nter periods ditions (day a out 80% of e remainder e vehicular fl y intense in mmer period sm one. Sin ars, the avera ling on the ro ad sections a no and Amal At last, on e.

d rockf

haracterized e of the Gulf cliffs and v m the coast, 50 m in ipal most has gths o as ding ous kfall pes, hich and the of and the of low the d is nce age oad and lfi), the

fall

by f of very the rel tha fav in the cau Jur ou wi pro set or to NE Al dis an pro po op ma ge cau AN cov con roc an 1). dep rai Oc det ve

4

Th Ha me Tr par (sl ch po sco par an giv R =

lief goes from an 600 m A vour the free the remaini e presence of use launchin On slopes rassic lime utcrop, some ith horizont omotes wedg t intersection more, corre slopes or wi E–SW trend lso caves an ssolution of l d karst disso ocess weak ortions, sepa pen discontin High cuts a ainly due to omorphology used by the NAS a total vering a tim nsider the le ckfall freque d 1.672 even . Rockfalls pending on infalls usual ctober and N tached bould getation ofte

The emp

he modified azard Rating ethod develo ansportation rameters are lope, clim aracteristics) oints is con oring system rameter is as d the final ven by: = fm +fh +f

m the sea lev ASL (Fig. 2) e fall of boul ng cases irre f ridges or be ng and reboun flanking the estones and times dippin al strata. T ge and/or pla ns and strati sponding to ith mutually ds, affect the nd very open limestones in olution is an ening, over rating the a uities. nd natural sl o the unfav y, climate, e roots of th of 15 rockf me span fro engths of the ency values nts yr-1 km-1 mainly occ n high-inten lly occurring November. S

ders that are en resulted fr

ployed roc

version of g System (m oped at the (CDOT) grouped int matic, geo ). A range v nsidered and m with a bas ssigned. The rating which fd +fc , vel until to h ). Almost v lders on the r regular rock enches with nding pheno e road, the d dolomitic ng less than The tectonic ane failures a ification. Th fractures str y intersecting he outcroppin n joints, due n several site n active geom r time, the adjacent roc lopes give ris vorable layo and joint he plants. U fall events w om 1996 to e ten road se (f) rangin can be calc curred in a nsity and s g during th Secondary fa e no longer rom summer

ckfall risk

f the Color mCRHRS) is Colorado D ) [7]. T to four separ ological, varying betw d using an se of 3, a ra en, these sco h defines th (1) heights greate vertical slope road, wherea faces, due t lower slope mena. cross-bedde c limestone the slope o c disturbanc along the join hree joint set riking paralle g NW–SE an ng rockmas e to chemica es are presen morphologica intact roc k walls wit se to rockfall out of joint enlargemen Using data b were recorded 2008. If w ections, mea ng between culated (Tabl autumn/winte short-duratio he months o alls of alread supported b wildfires.

k methods

ado Rockfa a qualitativ Department o Twenty-seve rate categorie and traffi ween 3 and 8 n exponentia

ating for eac ores are adde he risk (R) i er es as to s, ed es or ce nt ts el nd s. al nt, al ck th ls s, nt by d, we an 0 le er on of dy by

s

all ve of en es ic 81 al ch ed is

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F r w e ( c h c e r ( p w a s l s m u i ( p s o t a p o t b T c n i o n o d ( r c Fig. 2 – 3D map oad path. where fm, fh estimated roc (h), the d consequence The expo hazard fac characteristic event, climat rockfall hist (ditch effe percentage o width). Some and might subjective an lithology, no simultaneous masses outcr used, wherea in-matrix ma (in such a c present). As t specific rat outcropping r The RO.M to calculate affects peopl protection m of the numbe the road (Nr) by means of The identific cars, trucks necessary. T implemented occurrence o no accident i of a fatal a defining thre (As Low As rockfall risk computing t

showing the top

h, fd, and fc ckfall magnit ditch effec s of a possib onential scor ctors (slo cs, block siz te and prese tory) and to ectiveness, of decision e categories lead to ap nd approxima ot all of th sly. If sedim rop on the sl as if the dom aterial, then o case discont this study de ting parame rock masses MA. method the individ le that use t measures. The er of boulder ), defined on f the statistic cation of the s, buses, p Then, using d in the even of fatal accid is evaluated. accident is eshold values Reasonably k [4]. Thi the risk re pography of the s c are factors tude (m), the ctiveness ( ble failure (c) ring system ope height ze, volume ence of wate o the conse average sight dista are describe ppraisals wh ate. Dependi e 27 param mentary or c lope 18 para minant litholo only 12 param tinuities are eals with sed

eters pertin were analyz [8] was dev dual fatality the road, wi e first step i rs per year w n the basis o cal analysis e elements at pedestrians, a probabil nt tree analy dent, non-fat At last, the compared w s of unaccep Achievable) is approach eduction res

studied area with

s related to e failure haza (d), and ), respectivel applies to t, geologi of rockfall er on slope a equence fact vehicle ri ance, roadw ed qualitativ hich might ing on the slo meters are u crystalline ro meters must gy is the blo meters are ra obviously imentary roc nent to th zed. veloped in or risk that c ith and with

s the definit which can att f inventories of trajectori t risk regard

etc. is a listic approa ysis, the risk

al accident a calculated r with an aba ptable, ALAR and accepta h also allo sulting by h the the ard the ly. the ical per and tors isk, way vely be ope used ock t be ock-ated not cks, hese rder can hout tion tain s or ies. ding also ach k of and risk acus RA able ows the int me

5 m

W cal dir spr 1). Ac tra hig the roc hig gre ris red cau ch im fol see int Ve bet po roc 19 of per (R of cal tot eac per loc po vo roc of be me (co bo pa po an veh troduction o easures.

Results

methods

ith reference lculated for e rections (tow ring/summer . In fact, in t ctual Sight affic direction

gher the ratin e road there cks, “ditch e ghest rating eatest percen k. Also annu duction in th use the sco aracters, as mportant. A s llowing cate epage, deg terbedding, ehicle Risk tween about oints (in the r ckfalls affec 96 – 2008. With refere rockfall inv rformed by Rocfall v. 4.0 fallen bloc lculated. Th tal amount o ch simulati rformed alon cated in the ossible rockfa olumes of 0. ckfall hazard rocks hittin en calculated ean failure fr In order t onsequences oulder with v ssenger has ossible comb d vehicles: hicle/fallen of active

and com

e to mCRHR each of the t wards Posita r and autum the same roa

Distance (A ns, total ratin ng, the great e are no ditc effectiveness (81 points) ntage contrib ual precipitat he Decision ore increasi well as lau small contrib egories: ann gree of un block size, (AVR). The 500 (in the r road section n

ted this sect ence to RO.M entory data a y means of 0 by Rocscie cks (Pp) sto his percentag of 1,000 blo ion. Trajec ng 68 differ e ten road all hazard sc 1, 1 and 10 d that affects g the road p d by multiply requency (f) to consider ) arising fro ariable volum a fatal acc inations of i moving veh rock and s and passiv

mparison

RS, the total r ten sections i ano and Am mn/winter pe ad section, du ASD) values ngs may be ter is the risk

ches to reta s” is the fact ) and, cons bution to ov tion and the n Sight Dist ing, wherea unching feat bution is sup nual freeze– ndercutting, , friction, a e total final road section n. 9). A high tion during t MA. method and trajector f a dedica ence inc.), th opping on t ge was eval ocks (Nb) re ctory simul rent topogra stretches, a cenarios base 0 m3, respec the road (i.e per year and ying Pp by N

f).

the potent om the deta mes, the prob cident depen interaction b hicle/falling stationary v ve protectio

n between

rating (R) wa in both traffi mafi) and i eriods (Tabl ue to variabl s on the tw different. Th k. Since alon ain any falle tor having th equently, th verall rockfa Percentage o ance (PDSD as the slop tures are les pplied by th –thaw cycle degree o and Averag rating varie n. 7) and 84 her number o

the time spa d, on the basi ry simulation ated softwar he percentag the road wa luated on th leased durin lations wer aphic profile and for thre

ed on boulde ctively. Then e., the numbe d per km) ha Nb and by th ial outcome achment of bability that nds on thre between rock rock, movin vehicle/fallin on

n

as ic in le le wo he ng en he he all of D) pe ss he s, of ge es 43 of an is ns re ge as he ng re s, ee er n, er as he es a a ee ks ng ng

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rock. Probability values concerning the above-mentioned interactions were inferred from literature data [8]. Furthermore, to complete probabilistic calculations, in the manner provided for the event tree analysis, it is also necessary to consider the eventuality that a rock severely damages the road paving and that from this occurrence derives an accident to a travelling vehicle, with the result that a fatal accident may occur. For these probabilities, reference was done to data inferred from Italian Institute for Statistics (ISTAT), concerning the main causes of road accidents on the whole Italian road network [9].

The event tree analysis develops along twelve different paths and the probability of occurrence of each of them can be calculated from the product of each single event that constitutes the path itself. The final consequence of each path can be classified as: (i) fatal accident, (ii) non-fatal accident, and (iii) no accident. Summing probability values pertaining to paths characterized by the same final consequence, it is possible to obtain the annual probability of a fatal accident, non-fatal accident and no accident.

Using an Excel spreadsheet, probability values associated to the 12 paths of the event tree, for the above-mentioned hazard scenarios, were calculated. The following input data were needed: the number of rocks hitting the road per year (Nr), the length of the hazardous road section (Lr), the limit speed of the vehicles (Vv), the average vehicle length (Lv), the number of vehicles travelling on the road per day (Nv), the decision sight distance (DSD), as well probability values concerning interactions between rocks and vehicles. In output, the used spreadsheet allowed to obtain probability values concerning the 12 paths of the event tree, and the annual probability of a fatal accident, non-fatal accident and no accident.

According to [8], the risk reduction of a fatal accident due to protection devices installed along the road is given by:

Nr’ = (1 – C) x Nr , (2)

where Nr’ is the reduction in the number of falling rocks that may involve the road and C is the catching capacity of the structure, that is, the percentage of rocks that can be stopped by the protection device. Different C values were chosen according to literature data [8] and by means of a heuristic approach.

Finally, the risk affecting each road section, expressed as the annual probability of a fatal accident for the different three hazard scenarios and considering existing protection devices, has been assessed. For each road section, the total risk is given by the sum of partial risks related to the three hazard scenarios (Table 1). This risk ranges between 0 (road sections n° 4, 7 and 8) and 1.11x10-3 fatalities yr-1 km-1 (road section 1), whereas for the whole road stretch the computed mean value is 2.30x10-3. High risk values also affect the road section 9, with increasing risk levels as more severe hazard scenarios are assumed.

In order to compare risk values calculated by means of RO.MA. method with those concerning all car accidents resulting in almost a death in Campania, during the time span 1996-2008, available data from Italian Institute for Statistics were analysed [9]. With reference to this time interval, a mean value of about 330 fatalities/year or 3.41x10-2 fatalities yr-1 km-1 has been calculated: the length of the whole Campania road network (motorways, national and provincial roads) being about 9,652 kilometres. It is worth to note that the range of rockfall risk affecting the ten road sections is lower than the risk of car accidents on Campania Tab.1 – Final ratings and probability values of a fatal accident calculated for the studied road sections (with the existing protection

measures), by means of the mCRHRS and RO.MA. approaches, respectively. f is the mean rockfall frequency and Nr is the number of boulders hitting the road per year.

Road section Length of the road (m) Rockfall events

f Nr mCRHRS ratings RO.MA. method

spring/summer autumn/winter Fatal accident

towards Positano towards Amalfi towards Positano towards Amalfi No. of fatalities yr-1 km-1 1 375 1 0.205 1.02 677 677 671 677 1.11x10-3 2 360 1 0.214 1.28 831 831 831 831 1.43x10-3 3 225 1 0.341 2.04 795 795 795 795 2.07x10-3 4 275 0 0 0 561 561 555 555 0.00 5 280 3 0.824 3.29 801 801 795 801 3.60x10-3 6 310 2 0.496 1.48 783 783 777 777 8.10x10-3 7 350 0 0 0 501 501 501 501 0.00 8 380 0 0 0 651 651 651 651 0.00 9 230 5 1.672 5.02 843 843 837 837 5.11x10-3 10 260 2 0.591 1.18 783 783 777 783 1.41x10-3

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road network and, even thought is unacceptable, it results higher than the real risk of fatal accident caused by rockfalls, on the basis of the fatalities recorded since the construction of the Amalfitana road (1.65x10-4 fatalities yr-1 km-1).

Rockfall risk values affecting the studied road also are above the acceptability limit defined for “involuntary” risk, such as rockfalls, as proposed by Geotechnical Engineering Office of Hong Kong [8]. This means that in the study area, the individual risk is not acceptable, and some actions are requested in order to lower it. It must be considered that more effective countermeasures are required such as rockfall barriers and shelters.

Comparing results provided by means of the two procedures, it is possible to observe that high mCRHRS ratings affect the road sections at the same time characterized by probability values of about 10-3 fatalities yr-1 km-1. It is worth to observe that since the final rating R is given by the sum of several parameters, if as a result of RO.MA. method the risk of fatal accident is nil, due to the lack of rockfalls (see the road sections 4, 7 and 8), then R only measures the degree of potential damage along the road.

6 Conclusion

The assessment of rockfall risk, by means of the above-mentioned qualitative and quantitative methods, is affected by uncertainties and limitations that must be considered when using results for risk mitigation and planning purposes. The quality of rockfall hazard scenarios depends on various factors, including the accurate identification of rockfall sources and the correctness of trajectory simulations. Furthermore, the detachment areas of rockfalls are not always easy to identify and map precisely, and the trajectory simulation software, used in RO.MA. method, may locally overestimate run-out distances reached from boulders.

In the international literature there are no investigations concerning the main differences and similarities among the above-mentioned methods. Consequently, in order to compare results an attempt was performed on a road flanked by rock slopes characterized by complex geostructural and geomechanical layouts.

As far as the results for the mCRHRS are concerned, the rating calculated for each of the 10 sections is based on not many geological factors, qualitatively described and, therefore, are not reliable enough. Furthermore, this method is sometimes subjective and needs a good expert knowledge (heuristic approach). Partial ratings must

be correctly chosen according to the effective geological setting of slopes impending over the road.

With reference to RO.MA. method, since it allows to evaluate the risk both in presence and in absence of protection devices, it is an effective tool that is able to allow an easy comparison of the effectiveness of the various choices, in terms of risk reduction.

Finally, it should be kept in mind that mCRHRS is a “first-level” characterization system useful for subsequent detailed risk analyses which can be performed with the more efficacious RO.MA. method.

References:

[1] Pierson, L.A., Davis, S.A., Van Vickle, R.,

Rockfall hazard rating system implementation manual, Report FHWA-OR-EG-90- 01.

Federal Highway Administration, US Department of Transportation, 1990.

[2] Budetta, P., Assessment of rockfall risk along roads, Nat. Hazards Earth Syst. Sci., Vol. 4, 2004, pp.71–81.

[3] Morgan G.C., Rawlings G.E., Sobkowicz J.C., Evaluating total risk to communities from large debris flows, in: Geotechnique and natural

hazards Bi Tech Publishers, Vancouver, 1992,

225– 236.

[4] Peila D., Guardini C., Use of the event tree to assess the risk reduction obtained from rockfall protection devices, Nat. Hazards Earth Syst.

Sci.,Vol. 8, 2008, pp. 1441–1450.

[5] Pantelidis, L., A critical review of highway slope instability risk assessment systems, B.

Eng. Geol. Environ., Vol. 70, 2011, pp. 395–

400.

[6] Budetta, P., Nappi M., Comparison between qualitative rockfall risk rating systems for a road affected by high traffic intensity, Nat.

Hazards Earth Syst. Sci.,Vol. 13, 2013, pp.

1643–1653.

[7] Santi, P.M., Russell, C.P., Higgins J.D., Spriet, J.I., Modification and statistical analysis of the Colorado Rockfall Hazard Rating System,

Eng. Geol.,Vol. 104, 2009, pp. 55–65.

[8] Mignelli, C., Lo Russo, S., Peila, D., ROckfall risk MAnagement assessment: the RO.MA. approach, Nat. Hazards, Vol. 62, 2012, pp. 1109–1123.

[9] ISTAT, Anno 2013 Incidenti stradali in

Comparison between qualitative and quantitative rockfall risk methods for a hazardous road stretch

ADVANCES in ENVIRONMENTAL and

AGRICULTURAL SCIENCE

Proceedings of the 4th International Conference on Energy Systems,

Environment, Entrepreneurship and Innovation (ICESEEI '15)

Proceedings of the 4th International Conference on Agricultural Science,

Biotechnology, Food and Animal Science (ABIFA '15)

Dubai, United Arab Emirates

February 22-24, 2015

Scientific Sponsor

University of Naples Federico II, Italy

Energy, Environmental and Structural Engineering Series | 32

ISSN: 2227-4359

ADVANCES in ENVIRONMENTAL and

AGRICULTURAL SCIENCE

Proceedings of the 4th International Conference on Energy Systems,

Environment, Entrepreneurship and Innovation (ICESEEI '15)

Proceedings of the 4th International Conference on Agricultural Science,

Biotechnology, Food and Animal Science (ABIFA '15)

Dubai, United Arab Emirates

February 22-24, 2015

Published by WSEAS Press

www.wseas.org

ISSN: 2227-4359

ADVANCES in ENVIRONMENTAL and

AGRICULTURAL SCIENCE

Proceedings of the 4th International Conference on Energy Systems,

Environment, Entrepreneurship and Innovation (ICESEEI '15)

Proceedings of the 4th International Conference on Agricultural Science,

Biotechnology, Food and Animal Science (ABIFA '15)

Dubai, United Arab Emirates

February 22-24, 2015

Table of Contents

Authors Index

Comparison between qualitative and quantitative rockfall risk methods

for a hazardous road stretch

PAOLO BUDETTA, MICHELE NAPPI

Department of Civil, Architectural and Environmental Engineering

University of Naples “Federico II”

Piazzale Tecchio, 80 – 80125 Naples

ITALY

paolo.budetta@unina.it

michele.nappi@unina.it

1 Introduction

2 The studied road

3

e

3 Geologi

events

ical sett

ting and

d rockf

fall

4

The emp

ployed roc

ckfall risk

k methods

s

5

m

Results

methods

and com

mparison

n between

n

6 Conclusion