A new parameter for TBM data analysis based on the experience of the Brenner Base Tunnel excavation

Tunnel boring machine (TBM) operational data can be seen as a function of three main influences: the machinery of the TBM itself, the way the TBM is operated, and the excavated rockmass. Whereas the processing of TBM data must be done by computer-aided methods, the interpretation is typically done visually and is highly dependent on the user's prior experience. One way is to inspect the raw data itself, and another is to inspect computed parameters (specific penetration, specific energy or torque ratio). Either way, the goal is to find distinctive patterns that indicate changes in the rock mass conditions, and therefore it is crucial to find parameters that bear as much information as possible. The goal of this paper is to introduce the new parameter "theoretical advance force"(FNtheo ) that was developed in the course of systematic analysis of TBM operational data from the exploratory tunnel Ahrental Pfons (part of the Brenner Base tunnel project). FNtheo is back-calculated from the measured cutterhead torque and the measured penetration. The theoretical advance force shows very promising results with the data at hand, yielding more pronounced and well-defined patterns that correlate better with the encountered rockmass conditions than several other common parameters.