Analysis and prediction of TBM disc cutter wear when tunneling in hard rock strata: A case study of a metro tunnel excavation in Shenzhen, China

Disc cutter wear is the result of dynamic contact and friction between the tools and rocks in tunnel boring machine (TBM) tunneling. It can lead to a reduction in excavation efficiency, disruption of construction schedules, and extra costs. The geological indices, such as uniaxial compressive strength (UCS), Brazilian tensile strength (BTS) and Cerchar abrasion index (CAI), and the tunneling parameters, such as advance rate and rotation speed, were collected in the Shenzhen metro tunnel excavation project, and they have major effects on the cutter consumption rate. The wear data of 871 disc cutters over a 1592 m-long advance distance were analyzed. It was found that 87% of the disc cutters used were replaced due to normal wear, and the others were replaced due to abnormal wear. Flat wear mainly occurs for the disc cutters in the central area of the cutterhead, because they have a larger rotational resistance and eccentric loading due to their smaller rotational radius. The abnormal wear of the outer-area disc cutters mainly consists of forms of cutter ring cracking and bearing crushing owing to a higher rotation speed. A disc cutter wear prediction model was established to estimate the disc cutter consumption based on the plastic removal abrasiveness and motion analysis of the cutter rings. A rough linear correlation between the cumulative wear depth and the advance distance is found, and the wear rate varies during the tunneling progress due to the different geotechnical or construction parameters. The predicted wear is generally less than the actual wear, and the maximum prediction error is 49.4 mm. The predicted error is always larger for the disc cutters that have a high probability of non-uniform wear, especially for those in the outer area.