Wear Prediction and Mechanism Study of Tunnel Boring Machine Disc Cutter Breaking in Hard–Soft Rock Considering Thermal Effect

The TBM disc cutter cuts soft–hard composite strata during shield construction, and the cutter–rock cutting process generates high temperatures and severe wear. In this research, different strength types of rocks are taken as objects to analyse the interacting rock-breaking force and cutter motion model. The effects of rock properties on wear are investigated, and the cutter ring wear mechanism and damage types are discussed. Combined with the thermal stress theory of elastomer and the abrasive wear theory, a prediction model for cutter wear depth and wear mass is proposed. The results of the study show that the type of wear is dominated by abrasive wear, with the highest probability of uniform wear occurring in cutting hard rock. Hard rock is the most abrasive to the steel material of the cutter ring, and the percentage of abrasive wear decreases for cutting soft–hard composite strata. The amount of abrasive wear is negatively correlated with the hardness of the cutter ring. The rock damage patterns are different when cutting soft and hard rocks, and the wear areas are located at the bottom and sides of the cutter ring, respectively. Considering the thermal effect, the depth of wear for cutting hard rock has a power function relationship with the installation radius, which is closer to the actual value. The theoretical models are generally lower than the actual measured values. The wear prediction model is useful for determining the replacement interval of the cutter and improving the rock-breaking efficiency.