ORIGINAL PAPER Differential Hydrogeological Effects of Draining Tunnels Through the Northern Apennines, Italy Valentina Vincenzi • Alessandro Gargini • Nico Goldscheider • Leonardo Piccinini Received: 18 September 2012 / Accepted: 22 January 2013 Ó Springer-Verlag Wien 2013 Abstract Water inflows are a major challenge in tun- nelling and particularly difficult to predict in geological settings consisting of heterogeneous sedimentary rock formations with complex tectonic structure. For a high- speed railway line between Bologna and Florence (Italy), a series of seven railway tunnels was drilled through turbi- ditic formations, ranging from pelitic rocks with thin arenitic layers over sequences including thick-bedded sandstone to calcareous rocks showing chemical dissolu- tion phenomena (karstification). The tunnels were built as draining tunnels and caused significant impacts, such as drying of springs and base-flow losses at mountain streams. A comprehensive hydrological monitoring programme and four multi-tracer test were done, focusing on four sections of the tunnel system. The tracer tests delivered unprece- dented data on groundwater flow and transport in turbiditic aquifers and made it possible to better characterize the differential impacts of tunnel drainage along a geological gradient. The impact radius is 200 m in the thin-bedded sequences but reaches 2.3–4.0 km in calcareous and thick- bedded arenitic turbidites. Linear flow velocities, as determined from the peaks of the tracer breakthrough curves, range from 3.6 m/day in the thin-bedded turbidites to 39 m/day in the calcareous rocks (average values from the four test sites). At several places, discrete fault zones were identified as main hydraulic pathways between impacted streams and draining tunnels. This case shows that ignoring the hydrogeological conditions in construc- tion projects can cause terrible damage, and the study presents an approach to better predict hydraulic impacts of draining tunnels in complex sedimentary rock settings. Keywords Tunnel Á Groundwater Á Northern Apennines Á Turbidites Á Hydrogeological impacts Á Tracer test 1 Introduction High water pressures and water inflows represent major challenging of tunnelling. These water inflows are often difficult to predict both in terms of location and dimen- sion. High water pressures and/or large volumes of water inflows imply risks for workmen, lower the drillface stability, protract drilling time and increase construction costs (Schwarz et al. 2006). The importance of this problem is reflected in the amount of literature and the variety of methods to predict tunnel inflows, such as analytical solution (Goodman et al. 1965; Federico 1984; Lei 1999; Perrochet 2005; Zang and Franklin 1993; Hwang and Lu 2007; Perrochet and Dematteis 2007), numerical groundwater modelling (Mestat et al. 2004; Molinero et al. 2002), empirical relations (Cesano et al. V. Vincenzi (&) Consultant hydrogeologist, via O. Putinati 139/2, 44123 Ferrara, Italy e-mail: vincenzi.vale@gmail.com A. Gargini Earth and Geo-Environmental Sciences, Alma Mater Studiorum, University of Bologna, via Zamboni 67, Bologna, Italy e-mail: alessandro.gargini@unibo.it N. Goldscheider Division of Hydrogeology, Institute of Applied Geosciences, Karlsruhe Institute of Technology (KIT), Kaiserstr. 12, 76131 Karlsruhe, Germany e-mail: goldscheider@kit.edu L. Piccinini Geosciences Department, Padova University, via G, Gradenigo, 6, 35131 Padua, Italy e-mail: leonardo.piccinini@unipd.it 123 Rock Mech Rock Eng DOI 10.1007/s00603-013-0378-7