Rock Mech Rock Engng (2008) 41: 797–834 DOI 10.1007/s00603-007-0160-9 Printed in The Netherlands A spatial estimation model for continuous rock mass characterization from the specific energy of a TBM By G. Exadaktylos 1 , M. Stavropoulou 2 , G. Xiroudakis 1 , M. de Broissia 3 , H. Schwarz 4 1 Department of Mineral Resources Engineering, Technical University of Crete, Chania, Greece 2 Department of Dynamic, Tectonic and Applied Geology, Faculty of Geology and Geoenvironment, University of Athens, Greece 3 Technical Department, Bouygues Travaux Publics, Saint-Quentin-en-Yvelines, France 4 GISA Gesti o d’Infraestructures, S. A., Barcelona, Spain Received June 28 2007; Accepted November 14 2007; Published online 22 February 2008 # Springer-Verlag 2008 Summary Basic principles of the theory of rock cutting with rolling disc cutters are used to appropri- ately reduce tunnel boring machine (TBM) logged data and compute the specific energy (SE) of rock cutting as a function of geometry of the cutterhead and operational parameters. A computational code written in Fortran 77 is used to perform Kriging predictions in a regular or irregular grid in 1D, 2D or 3D space based on sampled data referring to rock mass classi- fication indices or TBM related parameters. This code is used here for three purposes, namely: (1) to filter raw data in order to establish a good correlation between SE and rock mass rating (RMR) (or tunnelling quality index Q) along the chainage of the tunnel, (2) to make predic- tion of RMR, Q or SE along the chainage of the tunnel from boreholes at the exploration phase and design stage of the tunnel, and (3) to make predictions of SE and RMR or Q ahead of the tunnel’s face during excavation of the tunnel based on SE estimations during excava- tion. The above tools are the basic constituents of an algorithm to continuously update the geotechnical model of the rock mass based on logged TBM data. Several cases were consid- ered to illustrate the proposed methodology, namely: (a) data from a system of twin tunnels in Hong Kong, (b) data from three tunnels excavated in Northern Italy, and (c) data from the section Singuerlin-Esglesias of the Metro L9 tunnel in Barcelona. Keywords: Rock cutting, geostatistics, kriging, TBM, RMR, Q, specific energy Correspondence: G. Exadaktylos, Department of Mineral Resources Engineering, Technical University of Crete, Chania, Greece e-mail: exadakty@mred.tuc.gr