Abstract
In tunnelling operations, Occupational Safety and Health (OS&H) and Environmental Protection of the areas close to the tunnel portal become even more critical in case of rock formations potentially containing asbestos, quartz, radioactive elements, etc. In order to limit the workers’ exposure and the environmental impact becomes in these cases of paramount importance to preliminarily analyze and quantify the possible presence of the pollutants in the rock and, if necessary, to implement suitable measures to avoid/minimize their emission from the winning and mucking operations. However, in case of asbestos minerals, to obtain reliable results from the preliminary analysis is a challenging task, due to the complex patterns of occurrence of asbestos within the host rock. Consequently, the definition of special monitoring, alarm and control systems is essential during the tunnel excavation. The paper summarizes the results of a thorough study aimed at defining the most suitable monitoring techniques in uncertain situations and the residual criticalities, essentially due to the delay between the beginning of the pollutant release at the tunnel face and its detection. The final part of the work deals with the possible innovative prevention solutions suitable to minimize the previously mentioned delay and ensure the safety of the workers along the time necessary to stop the activities and evacuate the tunnel, on hold of the activation of a special “asbestos” organization.
Highlights
According to the BIDPM (2008), any determination has imperfections giving rise to uncertainty in the result
The approach to tunnelling design must necessarily take into due account the possible presence of rock formations containing critical minerals, as typical in the NW Italian Alps. This situation can imply important problems in terms of Occupational Safety and Health (OS&H) and environmental impact, which both require special Risk Assessment and Management, corrective actions following exposure and dispersion into the common environment being clearly not acceptable
If the presence of asbestos is possible, the preliminary Risk Assessment from geological surveys and long exploratory drillings from the surface can exclude the presence of rocks potentially containing asbestos, but a no sure decision situations classification often remains
Summary
According to the BIDPM (2008), any determination has imperfections giving rise to uncertainty in the result. An uncertainty is formed by two components, namely, a systematic component and a random one. It is possible to quantify the effect of the systematic uncertainty and, if significant, to apply a compensating correction. In the case of underground infrastructures construction, the random effect can be much greater than in other industrial activities due to the nature of the input data, tunnelling involving natural elements that often show, at least on a local scale, not constant characteristics. The geological, hydrogeological and geotechnicalgeomechanical uncertainties (Eskesen et al, 2004; Peila, 2009) are here formed by a systematic component bound to the geological model and by a random component, due to the localized variability of the excavated rock, even involving the presence of hazardous substances and the deriving pollution of work places and environment
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