A method to estimate blast-induced damage in rock considering both stress waves and gas expansion phases is presented. The method was developed by assuming a strong correlation between blast-induced damage and stress wave amplitudes, and also by adapting a 2D numerical method to estimate damage in a 3D real case. The numerical method is used to determine stress wave damage and provides an indication of zones prone to suffer greater damage by gas expansion. The specific steps carried out in this study are: i) extensive blast monitoring in hard rock at surface and underground test sites; ii) analysis of seismic waveforms in terms of amplitude and frequency and their azimuthal distribution with respect to borehole axis, iii) measurement of blast-induced damage from single-hole blasts; iv) assessment and implementation of method to utilize 2D numerical model to predict blast damage in 3D situation; v) use of experimental and numerical results to estimate relative contribution of stress waves and gas penetration to damage, and vi) monitoring and modeling of full-scale production blasts to apply developed method to estimate blast-induced damage from stress waves. The main findings in this study are: i) both P and S-waves are generated and show comparable amplitudes by blasting in boreholes; ii) amplitude and frequency of seismic waves are strongly dependent on initiation mode and direction of propagation of explosive reaction in borehole; iii) in-situ measurements indicate strongly non-symmetrical damage dependent on confinement conditions and initiation mode, and existing rock structure, and iv) gas penetration seems to be mainly responsible for damage (significant damage extension 2-4 borehole diameters from stress waves; > 22 from gas expansion). The method has the potential for application in regular production blasts for control of over-breaks and dilution in operating mines. The main areas proposed for future work are: i) verification of seismic velocity changes in rock by blast-induced damage from controlled experiments; ii) incorporation of gas expansion phase into numerical models; iii) use of 3D numerical model and verification of crack distribution prediction; iv) further studies on strain rate dependency of material strength parameters, and v) accurate measurements of in-hole pressure function considering various confinement conditions.

The main objectives of this work were to investigate Geographical Information Systems techniques for modelling a cross-country trafficability. To accomplished stated tasks, reciprocal relationships between the soil deposits, local hydrology, geology and geomorphology were studied in relation to the study area in South-Eastern Sweden. Growing awareness of nowadays users of GIS in general is being concentrated on understanding an importance of soil conditions changed after cross-country trafficability. Therefore, in this thesis, constructing of the Soil Knowledge Database introduced to the genuine geological soil textural classes a new, modified geotechnical division with desirable for off-road ground reasoning measurable factors, like soil permeability, capillarity or Atterberg’s consistency limits. Digital Elevation Model, the driving force for landscape studies in the thesis, was carefully examined together with the complementary datasets of the investigated area. Testing of the elevation data was done in association to the hydrological modelling, which resulted with the Wetness Index map. The three distinguishable soil wetness conditions: dry, moist and wet, were obtained, and used consequently for creation of the static ground conditions map, a visible medium of soils susceptibility to for example machine compaction. The work resulted with a conceptual scheme for cross-country trafficability modelling, which was put into effect while modeling in GIS. As a final outcome, by combining all processed data together, derivatives were incorporated and draped over the rendered 3D animating scene. A visually aided simulation enabled to concretized theoretical, hypothetical and experimental outcomes into one coherent model of apprised under Multicriterial Evaluation techniques standardized factor maps for ground vehicle maneuverability. Also further steps of research were proposed.

在植被覆蓋的山區中，由於空載雷射掃描可穿透植被間縫隙的特性，有較高機會收集到植被下的地面資訊，因此適合作為製作植被覆蓋地區數值高程模型的資料來源，而在過濾過程中，一般僅利用點雲間的三維位置關係進行幾何過濾，而全波形空載雷射掃描可另外提供點位的波形寬、振幅值、散射截面積以及散射截面積數等波形資料，本研究將透過波形資料分析進行點雲過濾。 首先經最低點採樣後，本研究利用貝氏定理自動分析並計算得到地面點的波形資料的特徵區間範圍，採用振幅值、散射截面積以及散射截面積係數得到的特徵區間範圍開始第一階段的波形資料過濾，完成後再以第二階段的一般幾何過濾濾除剩餘之非地面點，最後的成果將與航測以及只採用幾何過濾時的成果比較。 由研究成果中顯示，不同的植被覆蓋間的單一回波波形資料的差異較明顯，最後回波類似。同一植被覆蓋下的單一回波及最後回波反應不同。而在成果的比較中，本實驗的成果與不採用波形資料輔助的成果大致相同本研究的成果在部分植被覆蓋的區域成果稍差，但透過波形過濾，可將幾何過濾所需計算的點雲數減少許多，可以增進整理過濾的效率。本研究的成果與航測相比時，在植被覆蓋區域較航測成果貼近實際的地面起伏，數值高程模型成果較為正確。 / In mountain areas covered with vegetation, discrete airborne laser scanning is an appropriate technique to produce DEMs for its laser signal is able to reach the ground beneath the vegetation. Once the scanned data was derived, point cloud filtering was performed based on the geometry relationship between the points at the processing stage. With the development of the advanced full-waveform laser scanning system, the additional waveform data has been proved useful for improving the performance of point cloud filtering. This research therefore focused on using the waveform data to extract DEM over vegetation covered area. The amplitude, backscatter cross-section and backscatter cross-section coefficient were the waveform parameters used to do the filtering. After initial waveform analysis was accomplished, an automated method to determine threshold range of each parameter representing ground points was proposed. By applying the thresholds, the original point cloud was filtered. Geometric filtering method was then used to eliminate the remained non-ground points. As a result, the DEM over the target vegetated area was derived. With the comparison against photogrammetric DEM and DEM derived from traditional filtering method, it was demonstrated that the quality of the resultant DEM was improved.

[pt] Um grande número de novos materiais geotécnicos foi desenvolvido baseado na adição de materiais fibrosos, sendo incorporados como elementos de reforço. A técnica de solo reforçado pode ser representada pela produção e aplicação, não somente de fibra natural, mas também de fibras sintéticas e poliméricas. Estudos anteriores de solos reforçados com fibras de polipropileno têm mostrado melhora significativa das propriedades mecânicas dos solos, tais como o aumento da resistência de pico e resistência pós-pico, ductilidade e tenacidade. Estes resultados mostram um grande potencial deste tipo de fibra, quando utilizado como reforço de solos, por exemplo, em base de fundações superficiais, aterros sobre solos moles e liners de cobertura de aterros sanitários. A partir de ajustes matemáticos para determinar a interação entre solos granulares e observações do comportamento global em macro-escala tornou possível analisar o comportamento de solos granulares reforçados com fibras de uma forma micro-mecânica. A modelagem numérica do comportamento mecânico de solos reforçados com fibras de polipropileno, através de uma análise micro-mecânica, utiliza como ferramenta o Método dos Elementos Discretos (MED), que permite a representação do solo em 2D, a partir de um conjunto de partículas de elementos discretos circulares. O MED descarta a visão clássica do solo como uma forma contínua, proporcionando a possibilidade de modelá-lo como partículas constituintes. Sua formulação baseia-se no equilíbrio de forças e de deslocamentos gerados pelos contatos, os quais são descritos através das leis da física clássica, permitindo o mapeamento dos movimentos de cada partícula. A vantagem da micro-mecânica é a possibilidade de explicitar microestruturas, tais como fibras de polipropileno, responsáveis pela mudança no comportamento do solo. Com base no estudo deste fenômeno, causado pela inserção de fibras de polipropileno em materiais granulares, formulações matemáticas foram propostas com a finalidade de descrever o comportamento de solos reforçados através da implementação do código de elementos discretos (DEMlib). Após a calibração e validação do programa, a influência decorrente da inserção do reforço de fibra ao solo foi analisada, sendo realizadas simulações de ensaios biaxiais em amostras discretas de areia, com e sem o reforço fibroso. O comportamento micro-mecânico de misturas reforçadas permitiu avaliar os efeitos das mudanças no teor de fibras presente na matriz de solo, bem como diferentes rigidezes das fibras. Conclui-se que o estudo realizado pelo Método dos Elementos Discretos identificou a real interação entre as partículas do solo e do reforço em forma de fibra, indicando que as fibras, quando inseridas no solo, podem sofrer deformações plásticas de tração e alongamento até atingir a ruptura, proporcionando a melhora nos parâmetros mecânicos do solo. / [en] A large number of new geotechnical materials was developed based on the addition of fibrous materials being incorporated as reinforcement. The technique of reinforced soil can be represented by the production and application, not only natural fiber, but also synthetic fibers and polymer. Previous studies of soil reinforced with polypropylene fibers have shown significant improvement of mechanical properties of soils, such as increasing the resistance peak and postpeak strength, ductility and toughness. These results show a great potential for this type of fiber, when used as soil reinforcement, for example, based on shallow foundations, embankments over soft soils and liners for landfill cover. From mathematical adjustments to determine the interaction between granular soils and the observation of global macro-scale become possible to analyze the behavior of granular soils reinforced with fibers in a micro-mechanics. The numerical modeling of mechanical behavior of soil reinforced with polypropylene fibers, through a micro-mechanical analysis, the tool uses as the Discrete Element Method (DEM), which allows the representation of the soil in 2D, from a set of particles circular discrete elements. The MED rule out the classical view of soil as a continuous form, providing the ability to model it as a constituent particle. Its formulation is based on the balance of forces and displacements generated by the contacts, which are explained through the laws of classical physics, allowing the mapping of movements of each particle. The advantage of micro- mechanics is the possibility of explicit microstructures, such as polypropylene fibers, responsible for the change in the behavior of the soil. Based on the study of this phenomenon, caused by the insertion of polypropylene fibers in granular materials, mathematical formulations have been proposed in order to describe the behavior of reinforced soils through the implementation of the Code of discrete elements (DEMlib). After calibration and validation program, the influence due to the insertion of fiber reinforcement to the soil was analyzed, and simulations of biaxial tests on discrete samples of sand, with and without the fibrous reinforcement. The micro-mechanical behavior of blends reinforced allowed evaluating the effects of changes in fiber content present in the soil matrix and different rigidities of the fibers. We conclude that the study by the Discrete Element Method identified the actual interaction between the soil particles and the reinforcement in the form of fiber, indicating that the fibers, when inserted into the soil, may undergo plastic deformation and tensile elongation until the rupture, providing an improvement in mechanical parameters of soil.

Denna studie handlar om hur unga män med utländsk bakgrund bosatta i socioekonomisktutsatta områden upplever massmedia och dess föreställning gentemot området de bor i. Studien är kvalitativ genom fokusgruppsintervjuer och berör frågor om hur dessa unga mänmed utländsk bakgrund beskrivs, hur massmedia talar om socioekonomiskt utsatta områdensamt hur massmedia spelar en roll i rapporteringen av dessa ovanstående faktorer. Vi kom fram till att dessa unga män med utländsk bakgrund bosatta i socioekonomiskt utsattaområden upplever att massmedia målar upp och reproducerar en övervägande negativ bild avde och området de bor i. De talar mycket kring sina egna känslor och hur upplevelsernapåverkar dem samt hur de speglar sig i deras liv.

La production de Modèles Numériques de Terrain (MNT) a subi d’importantes évolutions durant les deux dernières décennies en réponse à une demande croissante pour des besoins scientifiques et industriels. De nombreux satellites d’observation de la Terre, utilisant des capteurs tant optiques que radar, ont permis de produire des MNT couvrant la plupart de la surface terrestre. De plus, les algorithmes de traitement d’images et de nuages de points ont subi d’importants développements. Ces évolutions ont fourni des MNT à différentes échelles pour tout utilisateur. Les applications basées sur la géomorphologie ont profité de ces progrès. En effet, ces applications exploitent les formes du terrain dont le MNT constitue une donnée de base. Cette étude a pour objectif d’évaluer l’impact des paramètres de production de MNT par photogrammétrie et par InSAR sur la qualité de position et de forme de ces modèles. La qualité de position, évaluée par les producteurs de MNT, n’est pas suffisante pour évaluer la qualité des formes. Ainsi, nous avons décrit les méthodes d’évaluation de la qualité de position et de forme et la différence entre elles. Une méthode originale de validation interne, qui n’exige pas de données de référence, a été proposée. Ensuite, l’impact des paramètres de l’appariement stéréoscopique, du traitement interférométrique ainsi que du rééchantillonnage, sur l’altitude et les formes, a été évalué. Finalement, nous avons conclu sur des recommandations pour choisir correctement les paramètres de production, en particulier en photogrammétrie.Nous avons observé un impact négligeable de la plupart des paramètres sur l’altitude, à l’exception de ceux de l’InSAR. Par contre, un impact significatif existe sur les dérivées de l’altitude. L’impact des paramètres d’appariement présente une forte dépendance avec la morphologie du terrain et l’occupation du sol. Ainsi, le choix de ces paramètres doit être effectué en prenant en considération ces deux facteurs. L’effet des paramètres du traitement interférométrique se manifeste par des erreurs de déroulement de phase qui affectent principalement l’altitude et peu les dérivées. Les méthodes d’interpolation et la taille de maille présentent un impact faible sur l’altitude et important sur ses dérivées. En effet, leur valeur et leur qualité dépendent directement de la taille de maille. Le choix de cette taille doit s’effectuer selon les besoins de l’application visée. Enfin, nous avons conclu que ces paramètres sont interdépendants et peuvent avoir des effets similaires. Leur choix doit être effectué en prenant en considération à la fois l’application concernée, la morphologie du terrain et son occupation du sol afin de minimiser l’erreur des résultats finaux et des conclusions. / The production of Digital Elevation Models (DEMs) has undergone significant evolution duringthe last two decades resulting from a growing demand for scientific as well as industrial purposes.Many Earth observation satellites, using optical and radar sensors, have enabled the production ofDEMs covering most of the Earth’s surface. The algorithms of image and point cloud processing havealso undergone significant evolution. This progress has provided DEMs on different scales, which canfulfill the requirements of many users. The applications based on geomorphology have benefitted fromthis evolution. Indeed, these applications concentrate specifically on landforms for which the DEMconstitutes a basic data.The aim of this study is to assess the impact of the parameters of DEM production byphotogrammetry and InSAR on position and shape quality. The position quality, assessed by DEMproducers, is not sufficient for the evaluation of shape quality. Thus, the evaluation methods ofposition and shape quality and the difference between them are described. A novel method of internalvalidation, which does not require reference data, is proposed. Then, the impact of image matchingand interferometric processing parameters as well as resampling, on elevation and shapes, is assessed.Finally, we conclude on recommendations on how to choose the production parameters correctly,particularly for photogrammetry.We observe little impact from most of the parameters on the elevation, except InSAR parameters.On the other hand, there is a significant impact on the elevation derivatives. The impact of matchingparameters presents a strong dependence on the terrain morphology and the landcover. Therefore,these parameters have to be selected by taking into account these two factors. The effect ofinterferometric processing manifests by phase unwrapping errors that mainly affect the elevation andless the derivatives. The interpolation methods and the mesh size present a small impact on theelevation and a significant impact on the derivatives. Indeed, the value of the derivatives and theirquality depend directly on the mesh size. The selection of this size has to be made according to theforeseen application. Finally, we conclude that these parameters are interdependent and can havesimilar effects. They must be selected according to the foreseen application, the terrain morphologyand the landcover in order to minimize the error in the final results and the conclusions.

ix, 213 p. / The attacks on the United States of September 11, 2001, prompted scholars in a variety of fields, such as history, philosophy and literature, to re-examine the topic of terrorism, including the emergence of terrorism in West Germany in the 1960s and 1970s. The challenges that arise when dealing with the topic of terrorism derive in part from a lack of consensus on a definition for terrorists and terrorist attacks. One element that I found in my research is that there is a connection between terrorism and communication. This dissertation examines that connection in Volker Schlöndorff's filmDie Stille nach dem Schuss Gregor Schnitzler's film Was tun wenn's brennt Leander Scholz's novel Rosenfestand Ulrike Edschmid's biographical narrativesFrau mit Waffe: Zwei Geschichten aus terroristischen Zeitenin the context of Speech Act Theory. The films and texts show how West German terrorism is represented as a form of communication, through which fictional terrorists are trying to accomplish the impossible statement "I hereby persuade you." The act of persuasion has an element of freedom, because one can either be persuaded or not. However, the terrorists represented in the works mentioned above want to eliminate the element of choice and force the interlocutor to be persuaded. In order to achieve this they introduce violence, which in turn causes them to be labeled as terrorists. The more they try to use violence to achieve their goals, the more they cement their condemnation as terrorists. This dissertation frames its investigation within ideas about performative speech acts, concepts of power, violence, identity and discussions about "terrorist" narratives in German literature and film. / Committee in charge: Susan C. Anderson， Chairperson； Alexander Mathäs， Member； Dorothee Ostmeier， Member； Bonnie Mann， Outside Member

Ces travaux de thèse sont consacrés à l’examen du rôle du rayonnement thermique dans le processus de propagation des flammes issues de la combustion des particules d’aluminium dans l’air. Le sujet étant complexe et d’un intérêt industriel, il nécessite de prendre en compte le couplage de nombreux phénomènes physico-chimiques afin de prédire finement les conséquences des explosions de poussières. Une analyse bibliographique approfondie est proposée, concernant les mécanismes d’inflammation et de combustion des particules d’aluminium et aussi concernant les connaissances relatives à la propagation des flammes de poussières. La question spécifique de la nature des échanges thermiques et de l’influence du rayonnement thermique est étudiée. La revue bibliographique souligne les approximations et les hypothèses simplificatrices utilisées dans la littérature permettant donc de définir les pistes d’améliorations. Compte tenu des limitations importantes concernant la physique de ces flammes, un outil de simulation de physique numérique nommé « RADIAN », proche de la simulation numérique directe, a été développé proposant un couplage fin entre les différents modes d’échanges thermiques et la combustion pour modéliser la propagation de la flamme dans un nuage de poussières. La méthode des éléments discrets (MED) est utilisée pour modéliser numériquement les échanges radiatifs entre les particules et les échanges conductifs entre gaz et particules. La méthode des différences finies est utilisée pour modéliser numériquement la conduction thermique dans la phase gazeuse et la combustion. Un modèle radiatif est proposé se basant sur la théorie de Mie sur les interactions rayonnement-particules. Les résultats des simulations sont comparés avec des solutions analytiques et des données expérimentales de la littérature. Mais en plus, une étude expérimentale est aussi conduite afin de mesurer la distribution du flux radiatif devant la flamme et la vitesse de combustion laminaire pour des flammes Méthane-Sic, Méthane-Alumine et Al-air. Un bon accord entre les simulations et les expériences est démontré. La loi de Beer-Lambert relative au transfert radiatif devant le front de flamme s’avère inapplicable et une nouvelle solution analytique est proposée. La présence de particules absorbantes du rayonnement promeut la propagation de la flamme. En particulier, il a été montré expérimentalement et confirmé numériquement que les mélanges riches d’AL-air sont susceptibles d’accélérer rapidement. / In this thesis, the role of thermal radiation in aluminum-air flames propagation is studied. The subject being complex and of industrial interest, it requires the coupling of many physiochemical phenomena to accurately predict the consequences of dust explosions. A thorough literature review is proposed about the ignition and the combustion of aluminum particles and about the available theoretical models of dust flames propagation. The specific question of the nature of thermal exchanges and the influence of thermal radiation is studied. The bibliographic review underlines the simplifying assumptions and hypotheses used in the literature making possible the definition of improvement areas. Because of the limited amount of knowledge available to address these questions, a numerical tool “RADIAN” is developed enabling an accurate coupling between the different modes of heat exchange and combustion. The Discrete Element Method (DEM) is used to numerically model the radiative exchanges between particles and the gas-particle thermal conduction. The Finite Difference method is used to numerically model the thermal conduction through the gas phase and combustion. A radiative model based on Mie theory for radiation-particles interactions is incorporated. The results of the simulations are compared with available analytical solutions and experimental data. An original experimental study is also conducted to measure the distribution of irradiance ahead of the flame front and the laminar burning velocity for methane-air-Sic, methane-air-alumina and Al-air flames. A good agreement between numerical simulations and experiments is demonstrated. The Beer-Lambert’s law for radiative transfer in front of the flame front is found to be inapplicable and a new analytical solution is proposed. The presence of absorbing particles may promote the flame propagation. In particular, it is shown experimentally and confirmed theoretically/numerically that Al-air rich mixtures are likely to rapidly accelerate.

En tribologie, la modélisation numérique est aujourd'hui un outil indispensable pour étudier un contact afin de pallier les limites expérimentales. Pour comprendre de mieux en mieux les phénomènes mis en jeu, les modèles ne se situent plus à une seule échelle, mais en font intervenir plusieurs, rendant plus que jamais le concept de triplet tribologique incontournable. Travaillant avec cette philosophie et en se basant sur l'approche Non Smooth Contact Dynamics, dont nous rappelons les grandes lignes, nous proposons de franchir deux cas: proposer des modèles offrant des résultats quantitatifs et mettre en place les premières pièces d'une homogénéisation au niveau du contact (VER). Dans le premier cas, l'étude du couplage éléments finis/éléments discrets au sein d'une même simulation a pour but de proposer des modèles plus "réalistes". Même si l’interface utilisée est déjà présente au coeur du contact et ne va pas évoluer, elle permet de mettre en évidence l’utilisation d’outil de mesure permettant de lier le mouvement des particules aux instabilités dynamiques et permet d’avoir des résultats qualitatifs mais aussi quantitatifs puisque la comparaison avec les taux de contraintes expérimentaux sont en très bonne adéquation. Dans le second cas, le VER sous sollicitations tribologiques est étudié afin d'étendre les techniques d'homogénéisation aux problèmes de contact afin de s'affranchir de la description des interfaces aux grandes échelles en trouvant un moyen d'homogénéiser le comportement hétérogène de l'interface et de le faire dialoguer avec le comportement continu des corps en contact en faisant remonter, dans un sens, des grandeurs moyennées à l'échelle microscopique à l'échelle macroscopique des premiers corps et dans l'autre sens, se servir des données locales à l'échelle macroscopique comme conditions limites à l'échelle microscopique. / In tribology, the numerical modeling has become an indispensable tool for studying a contact to overcome the experimental limitations. To have a better understanding of the phenomena involved, the models are no longer located at a single scale, but involve several ones, more than ever, making the concept of tribological triplet as a unavoidable concept. Working with this philosophy and approach based on the Non Smooth Contact Dynamics framework, which we remind some outlines, we propose to cross two steps~: model that can offer quantitative results and that implement the first ingredient to perform a homogenization at a contact level. In the first case, the study of coupling finite elements/discrete elements within the same simulation aims to propose models that are more "realistic". Even if the interface is already present in the contact and not going to evolves, it can highlight the use of measurement tool of spot particles via dynamic instabilities and allows to have not only qualitative results but also quantitative ones since the comparison with the experimental strain rates are in very good agreement. In the second case, the study of VER in tribological charges is performed to extend the homogenization techniques to contact problems in order to overcome the interface description on large scales by finding a way to homogenize the heterogeneous behavior of the interface and make a dialogue with the continue behavior of bodies in contact by send up, in a sense, average values of the microscopic scale to the macroscopic scale and in the other sense, use local data of the macroscopic scale as boundary conditions at the microscopic scale.

En zones de montagne, l'aléa de chutes de pierre concerne à la fois les personnes, les infrastructures et les voies de communication. Différentes mesures de protection peuvent être envisagées pour réduire les conséquences de tels aléas. Certaines de ces mesures sont basées, totalement ou en partie, sur l'utilisation de la forêt comme structure de protection. Des structures de protections faites d'arbres abattus et laissés sur place peuvent également être utilisées pour améliorer ou maintenir la fonction de protection de la forêt suite à des travaux d'entretien forestiers, notamment. L'objectif principal de ce travail est d'étudier la capacité de protection de ces systèmes pare-blocs composés d'arbres en travers ainsi que de fournir des éléments d'aide à leur dimensionnement. Un modèle numérique basé sur la Méthode des Eléments Discrets (MED) a été développé pour étudier l'impact d'un projectile sur une tige de bois vert. Ce modèle permet de prendre en compte à la fois l'interaction bloc-structure à l’échelle locale du contact et la réponse dynamique de la structure « arbre en travers ». Des études expérimentales en laboratoire à petite échelle ont été menées pour calibrer et valider le modèle numérique. Le modèle développé a enfin été utilisé pour analyser l'efficacité des systèmes pare-blocs composés d'arbres en travers. La diminution de l'énergie du bloc suite à l'impact, la réponse de la structure, et son endommagement ont été analysés pour différentes conditions d'impact. Ces résultats ont permis d'établir des recommandations pour la conception de ces dispositifs de protection. / In mountain areas, natural hazards such as snow avalanches, landslides or rockfall threaten people and infrastructures. For this reason, civil engineering has proposed solutions to reduce the risk associated with such hazards. Despite the developments in this field, the protective capacity of forest is largely recognized. For rockfall hazard in particular, forests protection function is relevant as rock impacts onto trees lead to a significant rock energy loss. After forests maintenance tasks or windstorms the protection capacity of forests decreases. For this, felled trees are often left on the ground, in oblique position to compensate the decrease in the forest protection capacity due the forests stands density reduction. The main goal of this PhD research is to study the rockfall protection structures made of felled trees. Moreover, these investigations aim to provide recommendations for the design of such devices. A numerical model based on the Discrete Element Method (DEM) has been developed to study the dynamic response of fresh wood structures to impact. Laboratory experiments have been carried out to calibrate and validate the numerical developments. The DEM model implemented has been finally used to simulate real scenarii of rock impacts on simplified felled tree structures. These simulations have allowed identifying the most favorable configurations leading to a maximal loss of the rock kinetic energy during the impact onto a felled tree structure. Some improvements on the design of these structures are proposed to improve their capacity to dissipate the rock energy.