Primary and secondary tools’ life evaluation for soft ground TBMs

Abstract

Tool wear and tool life are very important issues for soft ground tunnel boring machines (TBMs) as they are directly related to the time and cost of tunneling. These issues may even become more important in planning costly interventions. In this regard, there are a few methods available to assess the tool life; however, the need for a thorough discussion and the development of new models is still highly demanded by the industry. This paper presents a summary of different methods for soft ground tool life, and tool wear evaluation. A comparative study is performed to indicate the predictability of available tool life evaluation methods based on the collected data from 23 soft ground TBM projects from around the world. Based on this database, new formulas are developed to evaluate tool life and tool wear for both primary and secondary cutting tools. The data analysis is conducted with single and multiple regression methods. The results show the equivalent quartz content and the standard penetration test are among the major influencing parameters for the evaluation of tool life of the primary cutting tools. In this regard, an estimation chart is generated for the quick evaluation of tool life for both earth pressure balance and slurry TBMs. The outcomes of this paper can be very useful in both the planning and construction stages of a TBM tunneling project where the intervention interval length and tool life/wear become critical decision-making factors for scheduling and cost evaluation and for reducing the risks of unwanted severe damage on the cutters.