Prediction of Rockfall Trajectories

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9 85 65 6 55 5 45 5 5 5 3 35 4 45 ÉCOLE POLYTECHNIQUE FÉDÉRALE DE LAUSANNE Predicio of Rockfall Trajecories

Two seps for he hazard assessme of «rock isabiliies» Acquire he bes possible kowlede of rockfall rajecories

1 ÉCOLE POLYTECHNIQUE FÉDÉRALE DE LAUSANNE Predicio of Rockfall Trajecories Predicio of Rockfall Trajecories Framework Basic feaures of compuer codes Example of rajecory aalysis Mouai Risks Workshop. Labiouse LABORATOIRE DE MÉCANIQUE DES ROCHES November 8h, 7 Difficulies i predici he block reboud Recommedaios Two seps for he hazard assessme of «rock isabiliies» Acquire he bes possible kowlede of rockfall rajecories Free, early verical fall of rock blocks Impac a op of a alus slope Deparure zoe Jumpi, rolli or slidi P failure P reach P failure P propaaio Propaaio P propaaio Deceleraio ad arres o he slope or by proecio measures

2 Aims of rockfall rajecory aalyses 4 kids of moio alo he pah. Delieaio of areas a risk (daer maps)? Maximum pah leh (ruou) Propaaio pah. Locaio of proecio measures ad choice of heir mai feaures? elociy Heih of bouce Bouce leh Eery v Flih v β Bouci Rolli v Slidi ω ω() v() β β v Bad udersadi ad predicio of he bouci pheomeo The bouci behaviour is overed by he eomery ad he mechaical characerisics of he slope he block Classificaio of rajecory codes Two caeories of prorams Riorous models cosider: 4 body wih is ow shape ad volume 4 all he moio, icludi roaio? Bu i depeds as well o he kiemaics a impac (velociy, collisio ale ) Lumped-mass models cosider: 4 block wih o mass or wih a mass coceraed i oe poi 4 he raslaio oly (o he roaio)

Classificaio of rajecory codes D 3 D Several formulaios o express he reboud of a block ad he coefficie(s) of

995] Les Créaux 3D ieresi for complex oporaphy I erms of eeries : ( ) ( ) ( ) m I ω ( ) ( ) ( ) ω m I ( ) ( ) (

is a measure of he ime-ieraed acio of he coac force perpedicular o he coac plae F F F () d F () d EBOUL- code -

elasic deformaios U ca be resored o he block, he oher par bei dissipaed i he roud : I I F yield m 3 3 F () d U

3 Classificaio of rajecory codes D 3 D Several formulaios o express he reboud of a block ad he coefficie(s) of resiuio I erms of velociies : Groud profile seleced i a verical plae or alo he lie of deepes slope [Azzoi & al, 995] Les Créaux 3D ieresi for complex oporaphy I erms of eeries : ( ) ( ) ( ) m I ω ( ) ( ) ( ) ω m I ( ) ( ) ( ) ( ) ( ) ( ) Aleraive defiiios of he resiuio coefficies EBOUL- code I I δ F 3 The ormal coefficie of resiuio is a measure of he ime-ieraed acio of he coac force perpedicular o he coac plae F F F () d F () d EBOUL- code - The soil is modelled wih a liear-elasic perfecly plasic behaviour U 3 F () δ() d Oly he par of eery relaed o elasic deformaios U ca be resored o he block, he oher par bei dissipaed i he roud : I I F yield m 3 3 F () d U yield The acio of he aeial compoe of he coac force F is accoued for by Coulomb s law of fricio : I yield F μ F () d μ I 3

4 Deermiisic aalysis e.. he maximum rockfall reach Probabilisic aalysis parameers sampled radomly i a expeced rae probabilisic disribuio Classificaio of rajecory codes 3 9 deparure zoe. deposiio zoe CETE Perceae of passi blocks Compariso of rajecory codes o 6 rockfall sies i he framework of a Ierre IIC projec «Cliff isabiliies» CETE Lyo - EPFL D lumped mass mehod deermiisic aalysis of he maximum ruou D lumped mass mehod radom parameers ad probabilisic aalyses 3D riorous mehod radom parameers ad probabilisic aalyses Toporaphical profile Oucroppi maerials Rockfall eve deachme of o 5 m 3 of limesoe limesoe bedrock wihou veeaio deposiio zoe e barriers Bieudro coarse debris, birches ad hazel rees sadsoe ad schiss of S. Chrisophe, o veeaio 4 cubic boulders from.3 m 3 o m 3 coarse debris, birches ad hazel rees road Aproz - Riddes Bieudro sie Cao of alais sadsoe ad schiss of S. Chrisophe, o veeaio meadow Rhôe river 9 deparure zoe Locaio of block edpois deposiio zoe Bieudro Perceae of passi blocks CETE 4

5 Afer he eve, he sie was secured by e barriers Siifica differece i velociy predicios deposiio zoe Perceae of passi blocks 5 m ood locaio of he barriers 3 kj Number of blocks Traslaioal velociy [m/s] CETE May facors ca affec he moio of a block afer impac The choice of appropriae resiuio coefficies codiios ood rajecory predicios Slope characerisics sreh siffess rouhess icliaio Block characerisics sreh siffess weih size shape iemaics Coefficies of resiuio ca o loer be cosidered as cosa parameers oly fucio of he slope maerial (as assumed by may compuer codes) raslaioal velociy roaioal velociy collisio ale cofiuraio of he block a impac Calibraio by meas of : i siu ess back aalyses Deermiaio from : experieces o oher slopes o he sie of ieres he lieraure o he basis of he slope maerial [Richards, Barbieri, Azzoi] Mos reliable ways Useful, bu ca be very misleadi 5

Predicive power of compuer prorams Correc predicios are codiioed by a ood calibraio of he parameers of he code o already experieced or moiored eves o he sie of ieres Grea cauio I he prese sae of

6 Predicive power of compuer prorams Correc predicios are codiioed by a ood calibraio of he parameers of he code o already experieced or moiored eves o he sie of ieres Grea cauio I he prese sae of kowlede, he mehodoloy of applicaio of rockfall simulaios o hazard mappi is sill o sraihforward ad more ha 3 rajecory rus were performed o desi adequaely he rockfall barriers Permae cocer o check he simulaio resuls wih sie observaios The resuls of compuer simulaios should be cosidered as a Decisio Aid Tool ad o as a absolue crierio 6

ÉCOLE POLY TECHNI QUE FÉDÉRALE DE LA USANNE. Fragmental rock fall paths:

ÉCOLE POLY TECHNI QUE FÉDÉRALE DE LA USANNE Frametal rock fall paths: Compariso of simulatios o Alpie sites Experimetal ivestiatio of boulder impacts V. Labiouse Moutai Risks Itesive Course LMR LABORATOIRE