Tracking of disc cutter wear in TBM tunneling: a case study of Kerman water conveyance tunnel

Disc cutters are the dominant cutting tools used in tunneling by rock TBMs. During the operation, disc cutters wear out and should be replaced with new ones. The wear rate of the disc cutters can be defined in terms of rolling distance/time and volumetric wear. Furthermore, the wear rate can be attributed to the mass loss. The wear prediction models for disc cutter have been developed on the basis of the intact rock abrasion indices, most commonly Cerchar abrasivity index (CAI). Examination of these models and comparing their results with actual wear observed in the Kerman water conveyance tunnel (KWCT) project show that the available models are conservative. In other words, reliance only on the intact rock abrasion does not offer an accurate prediction of the wear rate of the disc cutter. Therefore, rock mass conditions should also be considered in the calculations. The current study shows that volumetric mass loss is a more appropriate method to predict wear life of disc cutters due to consideration of various geometric parameters such as spacing between disc cutters, penetration rate, installation radius, and bored length. Subsequently, a new empirical prediction model is proposed by nonlinear multivariable regression based on CAI as a rock material parameter and RQD (rock quality designation) as a rock mass parameter to estimate the cumulative volumetric mass loss of disc cutters. For ease of using the model, a chart is introduced that determines the wear on the disc cutters based on the CAI and RQD.