Effects of geological materials on cutting performance of shield cutters

Exploring the effects of geological materials on the interaction law between shield cutters and strata helps to reveal the cutting mechanism and wear loss mechanism in complex strata such as sand and pebble strata. The linear cutting tests by using scraping cutters and PDC cutters were carried out with different geological types and strengths as control variables by analyzing the cutting forces and efficiency. The results show that: (1) The magnitude and volatility of cutting force increase with increasing aggregate hardness in the geological materials, and the increase in aggregate hardness makes the cutting process more discontinuous. (2) The optimum cutting depth decreases with increasing aggregate hardness, with optimum cutting depth of 4 mm, 5 mm and more than 6 mm for plain concrete, vitrified concrete and mortar, respectively. (3) The magnitude of cutting forces and their volatility increase with the strength of the geological material, and cutter intrusion is more difficult and cutting discontinuities increase at higher strengths of the geological material. (4) The optimum cutting depth for PDC cutters decreases as the strength of the geological material increases, with optimum cutting depths of 2 mm, 2.5 mm and more than 3 mm for cutting C50, C40 and C30, respectively. The characteristics of cutting efficiency variations are similar for circular PDC tools and tapered PDC tools. As circular PDC cutter is mostly tensile stress damage, resulting in a smaller specific cutting energy.