Abstract
In tunnel rock classification, seismic velocity has been long used as one of important classification indices. However, seismic velocities measured before and after excavation of the tunnel may differ largely, and as a result, there may be a large difference in the rock mass classification of the tunnel, and it is often imperative to change the tunnel support pattern at the time of construction. We have, therefore, studied a method to predict the seismic velocity and tunnel rock classification after excavation by applying rock physics models to geophysical data obtained in the site characterization stage before excavation. In this paper, we applied the proposed method to seismic velocity and resistivity profiles measured along the formation level of a planned tunnel and predicted P-wave velocity reduction due to loosening by excavation for estimating the tunnel rock classification after excavation. This application demonstrates that predicted and actual tunnel rock classifications agree each other very well.
