The geological reference model for the feasibility study of the corredor bioceanico aconcagua base tunnel (Argentina-chile trans-andean railway)

The Corredor Bioceanico Aconcagua base tunnel (CBA-BT) is a planned 53 km-long double pipe railway tunnel which will cross the Principal Cordillera of the Andean Thrust System under a maximum topographic cover of 2,000 m. The structural framework of the tunnel corridor is represented by a domino-style array of thrusts with ramp-flat geometry which detach along weak gypsum levels and stack diverse volcano-sedimentary terranes tectonically. As part of the CBA-BT feasibility study, the terranes crossed by the tunnel were mapped in detail and their component units were framed in a stratigraphic and palaeogeographic perspective overlooked by the earlier Geological Reference Model (GRM). Main results are: (i) the recognition of three different stratigraphic successions originally deposited in contiguous palaeo-domains of the Mesozoic Aconcagua Basin and (ii) the understanding of their mutual relationships; (iii) the description of thickness and lithofacies changes of the alluvial deposits of the Tordillo Formation; (iv) the re-interpretation of some gypsum levels, formerly referred to the Auquilco Formation, as part of the Mulichinco Formation (Mendoza Group). The implications of such advances on the GRM for a deep underground infrastructure are vast as they can help improve prediction of geological, structural and geomechanical data to excavation level, thereby contributing to implementation of future subsoil investigation, economic risk assessment and design optimization.