Design and Modelling by Discrete Elements of Tree-Anchored Rockfall Protection Fences

139 Pages·2017·4.95 MB·English

UNIVERSIDAD DE CASTILLA - LA MANCHA
E.T.S Ingenieros de Caminos, Canales y Puertos
TRABAJO FIN DE MÁSTER
Design and Modelling by Discrete Elements of
Tree-Anchored Rockfall Protection Fences
Autor:
Gonzalo de la Cruz Alcalá
No Expediente : 325014
Dirigido por:
Ignacio Olmedo Manich (GTS)
Franck Bourrier (IRSTEA)
Tutor académico:
Eduardo W. V. Chaves (UCLM)
Ciudad Real, Septiembre 2016

Acknowledgement
Finally, I have finished my Master’s Thesis. Now, I remember my first few
days in Lyon, in Grenoble... too many changes for a year. It had not been
easy, but I found a lot of people who trusted and helped me in making this
a successful year. Now, it’s time to acknowledge the support and help I
have received.
Firstly, I would like to thank my supervisors Ignacio Olmedo and Franck
Bourrier for giving me this opportunity and guiding me all along this thesis.
They have always been available (even in summer) to discuss every little
detail in this thesis. I thank you for having your trust on me since the
beginning. It has been a pleasure to work with you during these months. I
would like to extend my thanks to GTS, IRSTEA and the C2ROP, for the
organization of the project, their funding, all the resources provided for the
preparation of this thesis.
My gratitude also goes to David Bertrand who guided me during my
stay in Lyon and opened this door to me. Thank you for introducing me to
the research and for being so patient with me when I did not even speak a
word in French.
I would also like to give a mention to: David Toe, François, Sylvain,
Frédéric Jean Baptiste (merci pour la carte de la cantine), Stéphane and
Adel. Thank you for making me feel at home and for all the assistance
they have provided during the different phases of the project. It would have
been impossible to finish this thesis without your tips.
I thank my fellow interns at IRSTEA (Nico, Shashank, Scott, Olivier
and Amanda) for being not just partners but friends during my stay in
Grenoble. I could not even imagine this time without you. I will always
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remember the countless "pause café", your stories at "saava teen", how
strong is the Chartreuse or how cold is the snow when you fall skiing... For
all these reasons, thank you. Also I thank Diego y José (Ed, Edd y Eddy)
for their endless and funny discussions whenever I did not feel motivated.
With you I have always found a time to smile, forget the pressure and have
some fun. Thank you for being friends even at a distance.
Last but not the least, I would like to thank my whole family. You
have always been ready to help me even I did not ask. Thank you for your
guidance, for having supported every single decision I made throughout this
year abroad and my life in general.
A todos ellos, GRACIAS
Gonzalo de la Cruz Alcalá
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Abstract
In mountainous areas, the defence of communication routes and populated
areas against rockfall is guaranteed by protection structures. Due to their
easy installation procedure and their low environmental impact, flexible
fences are the most common solution for low to medium intensity events.
However, in forested areas the installation of such structures demands a
previous deforestation of the zone. In this context, in the framework of the
French national project C2ROP, G.T.S. is working to find a more ecological
solution for the protection of such areas. The novelty of this design consists
in the use of trees to anchor the fence instead of metallic posts. Thank to
this technical innovation, an important reduction of the construction costs
and environmental impact is achieved, since the installation usually takes
place in areas difficult to access for machinery, i.e.- with steep slopes and
dense forest.
The main goal of this Master’s Thesis is the study and development
of a numerical tool able to reproduce the mechanical behaviour under
dynamic loading of a new type of low-energy rockfall protection fences
in forested areas. Moreover, these investigations aim to provide technical
recommendations for the design and the installation of such structures.
This document describes the inception and the development of a
numerical model based on the Discrete Element Method (DEM). This
modelis calibrated usingdatafromlaboratoryteststo characterizethe main
components of the structure. In addition, full-scale real impact experiments
on the fence allow to validate the model comparing the numerical response
and the reality observed during the experimental campaign.
The numerical model is finally used to test different configurations
and to make a parametrical study which help, on one hand, to compare
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the influence of the different variables that enable the optimization of the
structure’s performance and, on the other hand, to provide evidence are the
key parameters to guide the future development of the DEM model.
Keywords: Discrete Element Method, Rockfall, Flexible Fences,
Protection Structures.
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Resumen
En regiones montañosas, la instalación de estructuras de protección
contra los desprendimientos rocosos es fundamental para la defensa de
infraestructuras de transporte y las áreas habitadas. Dada su facilidad de
montaje y bajo el impacto ambiental que genera, la solución más habitual
frente a eventos de media y baja energía, es el uso de barreras flexibles. Sin
embargo, en zonas forestales, la instalación de estas estructuras requiere de
la desforestación previa del área. Para evitar esto, G.T.S trabaja, dentro
del proyecto C2ROP, en la concepción de una nueva solución más ecológica
para la protección en zonas boscosas. En estas estructuras los postes de
acero son reemplazados por los troncos de los propios árboles situados en
el área de instalación. Esta solución técnica permitirá reducir el coste y el
impacto ambiental asociados a la construcción de estas estructuras, puesto
que se trata de lugares de difícil acceso para la maquinaria con fuertes
pendientes y una población arbórea importante.
El principal objetivo de este trabajo fin de máster es el estudio
y desarrollo de una herramienta numérica capaz de reproducir el
comportamiento estructural de las barreras forestales frente a solicitaciones
dinámicas. Del mismo modo, las investigaciones llevadas a cabo pretenden
aportar recomendaciones al diseño e instalación de dichas estructuras
En este trabajo se describe la concepción y desarrollo de un modelo
numérico basado en el Método de los Elementos Discretos(MED). Dicha
herramienta es calibrada mediante la realización de diferentes ensayos en
laboratorio para la caracterización mecánica de distintos componentes de la
estructura. Además, se han realizado ensayos de impacto a escala real que
permiten comparar la respuesta real y numérica
El modelo construido es finalmente utilizado para la realización de
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simulaciones de impacto en las diferentes configuraciones que se puedan
presentar y para la elaboración un estudio paramétrico. Este estudio tiene
un doble objetivo. Por un lado, estudiar las variables que posibilitan
la optimización del comportamiento y de los límites resistentes de la
estructura, y por otro, poner de manifiesto cuáles son los parámetros clave
para guiar el desarrollo futuro del modelo numérico.
Palabras clave: Método de los Elementos Discretos, Desprendimientos,
Barreras flexibles, Estructuras de protección.
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