The hydrogeological problems of disused mines in Olgiate Molgora (LC)

摘要

The object of this work is to evaluate more effective methodological approaches to face problems concerning areas affected by the presence of disused mining sites. Some years after the closure of mines, various problems as a consequence of disuse have come to light, and also, possibilities to use this resource with touristic and cultural aims have often been ignored. From the moment they have been closed mines can cause several problems, both for safety of the mine and of the neighbouring areas (downfalls, collapse of the vault, variations in the underground circulation, etc.) so it is necessary to evaluate more suitable techniques in order to maintain mines and prevent risks related to their presence. In order to deepen this subject we studied with particular detail a pilot area representative of the described problems: the Pelucchi Mine sited in Olgiate Molgora (LC). Several problems occurred in this abandoned area: the most important being that galleries have been troubled by water infiltration phenomena, starting from the lower part of the cavity. Previously the water was pumped away by the water pipeline until the water level was within acceptable limits, but when the extraction ceased water filled the cavities and saturated all materials around. This event caused a progressive alteration of the modalities of the underground water circulation, which in the future could cause instability phenomena on the surface and in the area near to the caves. In order to check the stability condition of these mines several analyses, either direct or indirect, have been made. Indirect analysis was made with the use of Satellite Radar Interferometry, to make a complete monitoring of surface movements (subsidence due to the collapse of caves), useful for the mine collapsed forecasting. Finally a phenomenological model has been made to define risk scenarios, necessary for Civil Protection aims and for the instability phenomena analysis.