Introducing an empirical model for prediction of disc cutter life for TBM application in jointed rocks: case study, Kerman water conveyance tunnel

Disc cutters wear and need to be replaced when using tunnel boring machines (TBMs) to excavate through rock, often becoming a high ticket item on the list of consumables in tunneling operation. The empirical models used for predicting cutter life are commonly based on the properties of intact rock, while the impact of rock mass characteristics on cutter wear is often ignored or not properly taken into account. Joints and discontinuities tend to decrease the strength of rock mass, as compared to intact rock. Joint properties can affect the interactions between the rock and the disc cutter in the boring process. In other words, the cutter wear and life in a jointed rock mass are different than the wear rate in intact rock. In this study, field data including the geomechanical parameters and observed cutter life in the Kerman water conveyance tunnel (KWCT) project was analyzed using multivariable regression to offer a new empirical prediction model for prediction of cutter life in the jointed rocks. The model presented in this study shows that cutter life is a function of the total fracturing factor and rock mass strength, representing rock mass properties and Cerchar abrasivity index as intact rock property. Furthermore, boring in jointed rock is easier than an intact rock, and as a result, the cutter life increases. The validation results show that this model can offer a more accurate prediction of the disc cutter life in tunneling projects involving jointed rock masses.