Hydrogeological hazards are very common when dealing with underground excavations, and they can bring about a damage both for the tunnel (e.g., tunnel inflow) and for the environment (e.g., water resource depletion). The paper proposes an example of the contribution of hydrogeology to risk management in tunnelling. In particular, the two following issues are addressed: how tunnel inflow can be assessed, and how its impact on water resources can be quantified. These issues are discussed based on the state of the art and with reference to an applicative example located northern Italy and excavated in sedimentary rocks at medium depth. A framework has been defined in order to: (1) identify the tunnel stretches affected by potential hydrogeological hazard, (2) quantify the tunnel inflow, (3) evaluate the changes in the hydrogeological balance and therefore assess the environmental impact. As far as tunnel inflow, different approaches have been used (empirical, analytical and numerical), pointing out that empirical methods are easy to use, but they can give only a qualitative evaluation of tunnel inflow; on their turn, analytical formulas provide a quantitative estimation, but results are often inadequate; numerical models can be useful for managing complex hydrogeological problems, but their results depend on the available input data. For the case study, monitoring data were compared to the values forecasted through the different approaches, obtaining different errors. Based on tunnel inflow rates, the changes in water balance can be evaluated in order to assess the environmental hydrogeological risk arising from tunnelling. The assessment was carried out for the case study with a stochastic approach, that involves the definition of critical thresholds.
From Hydrogeological Hazard Identification To Risk Assessment In Tunnelling: An Example In Northern Italy
Gattinoni P.;Scesi L.
2020-01-01
Abstract
Hydrogeological hazards are very common when dealing with underground excavations, and they can bring about a damage both for the tunnel (e.g., tunnel inflow) and for the environment (e.g., water resource depletion). The paper proposes an example of the contribution of hydrogeology to risk management in tunnelling. In particular, the two following issues are addressed: how tunnel inflow can be assessed, and how its impact on water resources can be quantified. These issues are discussed based on the state of the art and with reference to an applicative example located northern Italy and excavated in sedimentary rocks at medium depth. A framework has been defined in order to: (1) identify the tunnel stretches affected by potential hydrogeological hazard, (2) quantify the tunnel inflow, (3) evaluate the changes in the hydrogeological balance and therefore assess the environmental impact. As far as tunnel inflow, different approaches have been used (empirical, analytical and numerical), pointing out that empirical methods are easy to use, but they can give only a qualitative evaluation of tunnel inflow; on their turn, analytical formulas provide a quantitative estimation, but results are often inadequate; numerical models can be useful for managing complex hydrogeological problems, but their results depend on the available input data. For the case study, monitoring data were compared to the values forecasted through the different approaches, obtaining different errors. Based on tunnel inflow rates, the changes in water balance can be evaluated in order to assess the environmental hydrogeological risk arising from tunnelling. The assessment was carried out for the case study with a stochastic approach, that involves the definition of critical thresholds.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.