1. Dept. of Land, Environment and Geo-engineering, Tunnelling and Underground Space Center, Politecnico di Torino, Italy and, ICAG-CNR- Italian National Research Council (corresponding author). E-mail: daniele.peila@polito.it
2. Dept. of Land, Environment and Geo-engineering, Tunnelling and Underground Space Center, Politecnico di Torino, Italy.