ABSTRACT
TBM tunneling represents state-of-the-art excavation method for long alpine tunnels. This kind of tunnel construction is always associated with a considerable amount of uncertainty, having two major impacts on the TBM advance: various adverse occurrences at the tunnel face and imposing reductions of the achievable performance. The reduction is caused by the need to advance with sub-optimal operation parameters and the increased inspection and maintenance efforts. The second influence is given by the usage of additional measures in order to enable a safe TBM advance. The additional time required by encountering circumstances as described above can be hardly anticipated during the design phase. The model presented in this publication uses a very simple solution for the aforementioned issues: the construction activity during TBM advance is divided into three categories: regular advance, hindered advance and event-driven advance stop. A clear set of delimiting criteria is defined in the paper allowing a simple and objective identification.
