A Numerical Investigation of the Effect of Disc Cutter Wear on Rock-Cutting Forces in Mechanized Tunnel Boring Machines

Abstract

The wear of the disc cutter results in an increase in contact area with the rock, so when the wearing of the cutter exceeds its maximum limits, it should be replaced. However, this is not done on time because of cost concerns. Therefore, this study will investigate the effects of disc cutter wear on tunnel boring machine (TBM) operational parameters such as thrust force, torque, penetration rate, and specific energy as well as how it impacts advance rate and project time in hard rock TBMs. Finite-element modeling has been performed on 17″ disc cutters, calibrated with the results of linear cutting machine test (LCM). The wear values varied within the range of 0–20 mm and different penetration depths. Numerical results of normal cutting forces are compared with the previously suggested theoretical model, which shows good agreement. According to numerical models, normal and rolling forces are significantly increased as disc cutter wear increases. Increases in vertical and rolling forces are 130% and 75%, respectively. Changes in the side force on the disc cutters indicate that with the wear of the cutters, the result of the side forces is asymmetric and from the inside of the cutter. It causes the bearing system of the disc cutter to fail. The intensity of these asymmetric forces decreases as the installation radius of the disc cutter increases. Further, the wear of disc cutters significantly increases the specific excavation energy, resulting in a significant reduction in excavation efficiency. Finally, disc cutter consumption information for the Kani Sib water conveyance tunnel is also provided, which confirms the findings.