Structural analysis of Turtle mountain (Alberta) using digital elevation model: Toward a progressive failure

In 1903, the eastern slope of Turtle Mountain (Alberta) was affected by a 30 M m3-rockslide named Frank Slide that resulted in more than 70 casualties. Assuming that the main discontinuity sets, including bedding, control part of the slope morphology, the structural features of Turtle Mountain were investigated using a digital elevation model (DEM). Using new landscape analysis techniques, we have identified three main joint and fault sets. These results are in agreement with those sets identified through field observations. Landscape analysis techniques, using a DEM, confirm and refine the most recent geology model of the Frank Slide. The rockslide was initiated along bedding and a fault at the base of the slope and propagated up slope by a regressive process following a surface composed of pre-existing discontinuities. The DEM analysis also permits the identification of important geological structures along the 1903 slide scar. Based on the so called Sloping Local Base Level (SLBL) an estimation was made of the present unstable volumes in the main scar delimited by the cracks, and around the south area of the scar (South Peak). The SLBL is a method permitting a geometric interpretation of the failure surface based on a DEM. Finally we propose a failure mechanism permitting the progressive failure of the rock mass that considers gentle dipping wedges (30°). The prisms or wedges defined by two discontinuity sets permit the creation of a failure surface by progressive failure. Such structures are more commonly observed in recent rockslides. This method is efficient and is recommended as a preliminary analysis prior to field investigation.

Occupational exposure of truck drivers to dust and polynuclear aromatic hydrocarbons: a pilot study in Geneva, Switzerland.

The exposure to dust and polynuclear aromatic hydrocarbons (PAH) of 15 truck drivers from Geneva, Switzerland, was measured. The drivers were divided between "long-distance" drivers and "local" drivers and between smokers and nonsmokers and were compared with a control group of 6 office workers who were also divided into smokers and nonsmokers. Dust was measured on 1 workday both by a direct-reading instrument and by sampling. The local drivers showed higher exposure to dust (0.3 mg/m3) and PAH than the long-distance drivers (0.1 mg/m3), who showed no difference with the control group. This observation may be due to the fact that the local drivers spend more time in more polluted areas, such as streets with heavy traffic and construction sites, than do the long-distance drivers. Smoking does not influence exposure to dust and PAH of professional truck drivers, as measured in this study, probably because the ventilation rate of the truck cabins is relatively high even during cold days (11-15 r/h). The distribution of dust concentrations was shown in some cases to be quite different from the expected log-normal distribution. The contribution of diesel exhaust to these exposures could not be estimated since no specific tracer was used. However, the relatively low level of dust exposure dose not support the hypothesis that present day levels of diesel exhaust particulates play a significant role in the excess occurrence of lung cancer observed in professional truck drivers.

Characterizing emission and breathing-zone concentrations following exposure cases to fluororesin-based waterproofing spray mists.

Measurements and simulations were performed to assess workers' exposure to solvent vapors and aerosols during the waterproofing of a tiled surface. This investigation followed two recent incidents in the same company where workers experienced acute respiratory illness after spraying a stain-repellent resin containing fluorinated polymers on stone-tiled walls and floors. Because the waterproofing activity had been done for years at the tile company without encountering any exposure problems prior to these cases, it was strongly suspected that the incidents were linked to a recent change in the composition of the coating mixture. Experimental measurements and simulations indicated that the emission rate of particles smaller than 10 microm may be estimated at 0.66 mg/sec (SD 0.10) for the old resin and at 0.37 mg/sec (SD 0.04) for the new one. The measurement of the solvent emission rate from surfaces coated with the two resins indicated that shortly after spraying, the emission was in the range of 18 to 20 mg/sec x m2 and was similar for both products. Solvent and overspray emission rates were introduced in a two-zone compartment model. The results obtained in the near-field indicate significant exposure to overspray mist (7 and 34 mg/m3 for new resin) and solvent vapors (80 to 350 ppm for the new resin). It was also shown that the introduction of the new resin tended to significantly decrease the levels of solvents and particulates in the workers' breathing zone. These results strongly suggest that cases of acute respiratory illness are related to the specific toxicity of the fluorinated polymer itself. The fact that the same polymer is used in various commercial products raises concern regarding other possible occupational and domestic exposures.

Les composantes du risque : une entrée par les acteurs et le conflit lors de la mise en place des solutions : le cas de Los Chorros, Guatemala

Ce travail présente une étude de cas post-catastrophe à San Cristobal, Guatemala, où un important glissement de terrain du nom «Los Chorros» (8-10 millions de m3 de roche) affecte depuis 2009 diverses communautés et une des routes principales du pays. Les gestionnaires des risques, sur la base de leur propre évaluation, ont décidé de répondre d'une manière qui ne correspond pas aux intérêts de la population affectée. Les communautés locales ont évalué le risque de catastrophe et ont établi une autre solution suivant une conception du risque différente. Les conflits sociaux et la concurrence entre les différents acteurs du territoire, pour la définition des priorités et des solutions, révèlent les aspects sous-jacents de la société, utiles pour identifier et comprendre ce qui constitue le risque de catastrophe dans un contexte donné. Ce conflit montre que le risque de catastrophe n'est pas univoque mais un concept complexe, constitué par un grand nombre de composants. En termes de gouvernance, il met également en évidence la confrontation des savoirs et la tension qui peut exister entre les différentes approches du risque. Depuis une approche où le risque de catastrophe est considéré comme une construction sociale (les vulnérabilités étant historiquement générées par des processus sociaux, politiques, économiques et culturels), ce travail évalue d'autres modes d'interprétation, de traitement et d'intervention qui peuvent aider à améliorer les méthodes d'évaluation et de gestion des risques. Enfin, la proposition de gestion qui découle de l'exemple guatémaltèque invite à une autre manière de concevoir la gestion des risques en intégrant les différentes conceptions du risque et en visant une coordination stratégique entre les acteurs des politiques publiques, les échelles d'intervention, les experts en charge des différents aléas et la société civile, afin d'obtenir une solution acceptable pour tous les acteurs impliqués dans un territoire. -- This work analyses a post-disaster case study from San Cristobal, Guatemala where a large landslide named "Los Chorros (8 millions cubic meters of rock) affects several communities and one of the country's main west-east access highways. Risk managers, starting from their own assessment, decided to respond in a way that does not correspond to the interests of the afected population. Local communities assessed the risk disaster situation and establised another solution from a different conception of risk. These social conflict and competition for priorities and solutions for risk management reveal that disaster risk is not unequivocal but a complex and holistic concept, constituted by a large set of components. From a social constructivism approach, where disaster risk is considered as the results of social, political, economic and historic process, this thesis evaluates other modes of interpreting, shaping and managing risk that can help improve methods of risk assessment and management. Studying the logic of action of actors, who mobilize to establish a solution, enables to identify as to what constitutes a disaster. For this reason, the study focus, in particular, on the analysis of practices (practical science) implemented by all actors in San Cristobal Altaverapaz. Finally, it puts into perspective the risk management in terms of an integrative approach for policy experts that find compromise between different conceptions of risk in order to obtain a solution acceptable to all those involved.