Study on the failure mechanism and cutting efficiency of rebar in linear cutting based on the finite-discrete element method.

The design of cutter parameters plays a key role in the successful cutting of large-diameter reinforced concrete building piles by shield machines. However, the cutting mechanism of the shield machine in cutting rebar is not clear. Based on the shield pile cutting project of Wuhan Metro Line 12, the finite-discrete element method (FDEM) numerical models of rebar cutting are established. The cutting force, rebar failure and stress evolution of rebar in linear cutting with different blade angles (a) are analyzed. By calculating the cutting area and cutting work, the relationship between the cutting specific energy and the a is obtained. Results indicate that the maximum peak cutting force increases as a increases and the maximum principal stress and shear stress are concentrated in the rebar near the cutter. As a increases, both the cutting surface roughness and cutting work increase, and the number of tensile and shear cracks also increases. However, the cutting specific energy decreases first and then increases with the increase of a, which has the lowest value and the highest cutting efficiency with a of -10°. The simulation results indicate that a of -10° can effectively improve the shield machine performance, which is also supported qualitatively by the project case.