ABSTRACT
The speeds of TBM tunnelling and drill-and-blast tunnelling are compared, using the new QTBM model for TBM performance estimation, and the conventional Q-value for drill-and-blast prognoses. By using these two methods it can be estimated whether a hybrid solution might be the most economic and timely. For instance one would drill-and-blast the most problematic ground, if early access was feasible, while waiting for TBM delivery. A hybrid solution was used at the 18 km long Qinling Tunnel in China, and is also planned in Brazil, where abrasive, massive rocks occur at both ends of the tunnel. Logging methods that can conveniently be used to describe the ground, including the use of seismic, are described in this paper, together with some of the details of the QTBM method, including a worked example.
