Abstract
TBM (Tunnel Boring Machine) is widely used in tunnel construction. As the key component of TBM, disc cutters show rapid wear and frequent failure when TBM excavating in hard rock. Many studies have been delivered to clarify the mechanism and predict the normal wear rate of disc cutters but unable to recognize the abnormal failure such as cutter chipping. In this paper, the characteristics of cutter chipping is analyzed based on field investigation at first. The field statistics of YHJW project show that gauge cutter is most vulnerable to chipping, followed by center cutter, and the face cutters are replaced mainly because of normal wear. Rock property, initial state of disc cutter, penetration rate of disc cutter and characteristics of cutter's movement are the four basic influencing factors of cutter chipping. The results indicate that (1) the ratio of cutter chipping increases with the increase of rock strength; (2) initial wear on the surface of the cutter ring and usage of old bearings lead to most of the cutter chipping; (3) the higher the penetration rate of disc cutter is, the higher the probability of cutter chipping is. When the penetration rate of disc cutter reaches 0.3mm/s, the probability of cutter chipping could be 40%; (4) the existence of both sliding and rolling makes the cutter ring in a disadvantageous stress state. The larger the sliding part is, the more serious the cutter chipping is. Further research is still needed to study the mechanics mechanism and micro-evolution process of cutter chipping.
With the increasing demand for deep-buried long tunnels, TBM tunneling in hard rock is becoming more and more frequent. The disc cutter wears fast and abnormal damage occurs frequently due to the tremendous pressure when propelling the rock and the friction with the cutting face. Increased number of cutter replacement leads to increased costs and reduced tunneling time.
