Currently there is no uniform and consistent documentation of unexpected standstills available, which can be applied during the excavation of tunnels with tunnel boring machines (TBM). Such a documentation and evaluation would be helpful for the estimation of risks, costs and the advance rate for future tunnels excavated with a TBM. An approach for a documentation of unexpected standstills of hard rock tunnel boring machines, such as open gripper TBM, single shield TBM and double shield TBM, was developed at Graz University of Technology. This paper shows the results as well as the benefits of a detailed and continuous event documentation during tunnel excavation. The new approach can be taken as a basis for future documentation of unexpected standstills in TBM tunnelling.
Nowadays large infrastructure projects with long tunnels, such as the Semmering base tunnel or the Brenner base tunnel in Austria, are in planning state or under construction. The length of such tunnels as well as the advantage of a fast excavation in favourable rock mass conditions make the use of a tunnel boring machine more and more important.. As for conventionally excavated tunnels, an excavation with a tunnel boring machine demands a detailed estimation of costs, risks, advance rates and construction time in advance, too. Boundary conditions have to be identified as exactly as possible in order to choose the most suitable machine type. Therefore, a detailed and continuous documentation of unexpected standstills of the tunnel boring machine applied during excavation would provide a proper basis for the design of future TBM driven tunnels. The documentation needs to be done contemporary. Reasons for standstills must be evaluated and interpreted. In addition to the documentation of the standstill reason, implemented measures to resume excavation again, have to be documented. Figure 1 shows a flow chart of such a documentation and the use of gained experience for future projects.