Study of common wear prediction models for hard rock TBM disc cutters and comparison with field observation in Kerman water conveyance tunnel

Disc cutters are the most commonly used cutting tools in the hard rock tunneling by tunnel boring machines (TBMs). During operation of a TBM in any project, disc cutters wear out and should be replaced to maintain high machine performance. This is especially true in very strong and abrasive rocks. In the process of planning and estimation of completion time and cost for a given tunneling project, the lifetime of the disc cutter is often predicted using the empirical models due to their simplicity and availability. But understanding the background of the models and the relative difference between both predicted and actual lifetimes is critical for improving the accuracy of estimated cutter life. In this study, the basis and input parameters of the most frequently used empirical models for prediction of disc wear life are examined. The result of estimating cutter life by using these models is compared in similar working conditions, including TBM specifications, operating conditions, and rock abrasivity. The results show that in slightly abrasive rocks, the empirical models should be carefully chosen, because the estimated disc life may spread over a wide range. Furthermore, some models are very conservative, while others offer more compatible estimates with the rock abrasivity. Also, in the Kerman water conveyance tunnel, the predicted and actual cutter lives show good correlation with the ratio of the rock mass and intact rock strengths, in addition to laboratory measures of rock abrasivity.