ABSTRACT
One of the main hazards during TBM excavation in hard rock is related to unforeseen adverse conditions such as faulted rock masses. Different methods for geotechnical investigations ahead of the tunnel face are used in TBM tunneling. Many of these methods imply an interruption of excavation and their systematic application leads to significant delay. The continuous analysis of TBM excavation parameters may represent an interesting tool for monitoring of geotechnical conditions at the tunnel face and for early detection of adverse conditions. This work presents the feedback from the Tunnel 4 (Angat Water Transmission Improvement Project, Philippines) a 6.4 km long water transfer tunnel excavated by double shield TBM. During excavation, Es and FPI have been systematically analyzed and compared with RMR values. After a test section, reference values of Es and FPI were defined for each RMR-class and used for monitoring of ground conditions at the tunnel face.
