Lo scavo con TBM della rimonta del Progetto Premadio II in Alta Valtellina (Prov. di Sondrio): confronto tra le previsioni progettuali, i dati macchina e le condizioni geomeccaniche degli ammassi rocciosi scavati

The note reports the results of a geomechanical survey carried out along the tunnel, at a 45° slant and 827 meters in length dug to house a new pressure water pipe as part of the Azienda energetica milanese (Aem S.p.A.) Premadio II project in the Upper Valtellina (Province of Sondrio). The project includes a number of works with the aim of substantially strengthening the existing hydroelectric power station at Premadio. The excavation was done by the Quadrio Curzio S.p.A. Company of Milan using an unshielded full section cutter.
The results of the geomechanical analysis were compared both with the analysis of the forecasts drawn up at the planning stage, and with the performance parameters of the cutter recorded during the excavation. The comparative examination of a series of parameters provided indications regarding how thorough the geognostic investigations were and what technical decisions werw taken with respect to carring out the excavation.