Cutting tool wear prognosis and management of wear-related risks for mix-shield TBM in soft ground

The wear of cutting tools is a major issue in Mix-Shield tunneling in soft ground, because it is the most common reason for intermission of advance. Thereby the costs for the downtime commonly exceed the costs for the changed cutting tools. However, due to the inaccessibility of the processes involved and the variety of influencing factors, there are no prognosis tools available, that provide reliable information on cutting tool life. With the detailed data analysis of 18 Mix-Shield TBM drives, this paper takes an empirical approach to tool wear in soft ground. The data analysis results in a qualification and quantification of the relevant influencing factors on cutter tool life. This leads to a prognosis model for cutter life in soft ground for Mix-Shield TBM, based on empirical correlations with soil parameters and TBM design and advance parameters. For a realistic approach the model is completed by an engineering process to translate the cutter life into distances for intermission of advance and required amount of cutting tools to be changed.