News, congress IAEG XII 2014 inTourin on Rockfall risk assessment and management - current practice and developments.
Thank you to John D Duffy from DOT of California (USA) for this interesting news. The book published form Transportation Research Board (TRB).
I attended in october 2012 the full scale test organized by Maccaferri Spa and Risp Srl in the field test facility of Fonzaso - IT.
The test on rockfall barrier (RMC P650) with 6500kJ energies, post height 6.5m, impacted by boulder of 17666kg dropped from a height of 38.25m.
The video beolwe granted from Risp Srl, describe the event.
In the last 10 years I have seen a lot of 1:1 test on rockfall barriers but this was impressive for two reasons:
My point of view regarding the symmetric behavior is due to large number of brakes elements (with short eleongation, aprx 1.0m, ) distributed on the structure RMC P650 that guarantees an optimal distribution on forces in space and time of deceleration.
The bounce of boulder indicates (for my opinion) that rockfall barriers still has many structurals reserves....this is positive because the technical limits on rockfall barriers must and can still be reached.....good work to the producers...
What do you think?
I was invited by Geobrugg to attend a revolutionary test 1:1 in Winterthur (CH) October 9, 2012. It was a full-scale test to verify/ceck the behavior of the flexible steel mesh on a platform that simulates a slope landslide. Video procedure are linked belowe.
I seem to be back at the beginning of 90’s with the first full scale tests on rockfall barriers organized form Tubosider in France, Igor in Italy and Geobrugg in Switzerland. After 20 years of test 1:1 on rockfall barrier could be organize a “Technical Guideline to 1:1 test on felxible nettings” to standardize the procedure to test in full scale the nettngs on slops? What do you think?? Thomas
In many cases the rockfall protection barriers must adapt to the conditions of the terrein. One of the points that require greater attention and detail to guarantee the structural strength of the rock barriers is te deviation on lower lateral cable. In the drawing belowe you can see two typical case but not the only one. You may need to resolve deviations elevation (as in drawings) and planimetric.
Case n°1: lateral lower cable deviation
Case n°2: intermediate lower cable deviation
....after the Guideline ETAG027/2008, the variation of geometry of the rockfall barriers respect to the tested barrier will be guaranteed by the manufacturer with special calculation as as described in chapter 4.3:
"If for local reasons of the natural site it is necessary to have a different geometry from the test site geometry a specific design shall be provided. Forces acting in the structure should be evaluated to demonstrate the fitness for use of the falling rock protection kit. The producer, under its own responsibility, shall provide geometric tolerances in the installation book with special references to the spacing of the posts and the inclination of the main ropes".
I don't understand if the responsibility to define what forces act on the modified structure are in charge of the manufacturer or designer???
And today for my experiences I've never found a manual with described tolerances permitted for the deviation of lower/lateral cable.
Who can clarify this issue?
In last years, expecially in United States and Canada a new type of rockfall protection system has developed.
These new barrier are usually called "rockfall attenuator" or "hybrid barrier". The reason for these two definition are:
For my point of view is better the terms "attenuator barrier" is a more intuitive terms to explain the behavior of structure.
Where the zone to protect has before a sufficent area of possible accumulation of block, the AB (attenuator barrier) will be interesting; with this system the block are not stopped but guiding down along the slops and accumulated at the foot of slops. Another interesting aspect of this barrier is the reduction of maintenance and the capacity of auto cleaning.
In this drawings belowe are be explained the behavior.
Here you can find some detail directly from the web:
Others contributors will be appreciated
l giorno 30 Novembre 2012 a partire dalle ore 14:00 a Bolzano avrà luogo a Bolzano il "Primo Incontro delle Commissioni in Ingegneria Geotecnica degli Ordini degli Ingegneri".
L'evento è patrocinato da AGI e CNI.
Recently news on high energies rockfall protection barrier has opened a discussion on the energy lmitis of the rockfall protection steel barrier.
Many people have asked me this: is a 8000kJ barrier equal to two allignment of 4000kJ barriers when impacted from the same block?? (see the image belowe).
The answer is very difficult and dipending to differnet factors.
To try answer I make before some considerations (we refer for example to ETAG027 guideline procedure testing):
For this reasons, if the impact energy is greater than the MEL Energy of the barrier, we can't say that (see drawing belowe):
For this reason my firs answer is that 4000kJ+4000kJ is different than 8000kJ in terms of behavior of structure..... but I don't know if 4000kJ+4000kJ is greater or lesser than 8000kJ.
In a next post I try to find a model to calculate the energy exit of the rockfall barriers (E-out) and try to answer to the question.
Discussion open !!!
Until now, the protection systems against rockfall for high energies (greater than 5000kJ) were rockfall embackments with or without geogrid and rockfall galleries ..... will not be as ... a new system of rockfall barrier in steel insert in this level of protection energy. The 8000kJ height 8.5m barrier of Geobrugg AG has achieved a new record.... congratualtion to all the staff of Geobrugg AG for this interesting news...
Grazie a Fabio De Polo della Provincia di Bolzano per questa interessante segnalazione di convegno che si terrà a Bolzano il prossimo venerdì 23/09..... qui trovate il programma.
Di interesse l'intervento del Prof. Facciorusso dal titolo: "Risposta sismica locale e fenomeni di instabilità dei versanti".
Stephan Lambert form Cemagref and also member of Rockfall Specialist Network in Linkedin has informed me of the publication of this interesting book "Rockfall Engineering" which you can order here and with this content:
2. Remote Sensing and Monitoring Techniques for the Characterization of Rock Mass Deformation and Change Detection, Marc-Henri Derron, Michel Jaboyedoff, Andrea Pedrazzini, Clément Michoud and Thierry Villemin.
3. Mechanical Stability Analyses of Fractured Rock Slopes, Véronique Merrien-Soukatchoff, Jerôme Duriez, Muriel Gasc-Barbier, Félix Darve and Frédéric-Victor Donzé.
4. Assessment of Constitutive Behaviors in Jointed Rock Masses from a DEM Perspective, Cédric Lambert and John Read.
5. Methods for Predicting Rockfall Trajectories and Run-out Zones, Luuk Dorren, Ulrik Domaas, Kalle Kronholm and Vincent Labiouse.
6. Rockfall Dynamics: A Critical Review of Collision and Rebound Models, Franck Bourrier and Oldrich Hungr.
7. Rockfall Hazard Zoning for Land Use Planning, Vincent Labiouse and Jacopo Maria Abbruzzese.
8. Rockfall Quantitative Risk Assessment, Jordi Corominas and Olga Mavrouli.
9. Multi-scale Analysis of an Innovative Flexible Rockfall Barrier, Ayman Trad, Ali Limam, David Bertrand and Philippe Robit.
10. A New Design Method for Rockfall Shelters Covered by Granular Layers, Francesco Calvetti and Claudio Di Prisco.
11. Design Procedure for a Three-Layer Absorbing System in Rockfall Protection Galleries, Norimitsu Kishi and Hisashi Kon-No.
12. Ground Reinforced Embankments for Rockfall Protection: From Real Scale Tests to Numerical Modeling, Daniele Peila.
....good reading for all specialists....
For many people it is difficult to understand the motion concept of rocks along the slopes, in this interesting video shot in New Zealand (Christchurch) from GNScience Chris Massey analyses rockfall hazards to assist Christchurch recovery planning and discusses many issues related to unpredictable prevents this phenomenon.
At 4.17 minute of the video is very interesting to observe the deviation of the block (aprx. 40 °) respect the line of maximum slope angle ........ only for a little impact point with a rock outcrop present on the slope.!!!!!
This is very difficult to take into account with the rockfall analisys two dimensional and probably for this type of activities the better solutions is the 3D software.
In any case for my experiences the rebounding height is much more unpredictable than the rock energy. For this reason, my assumption design of heght protection measures is based on model described belowe.
Probably can be other parameter to take in accont and in this way are welcome advice on other experiences.