Abstract: In order to explore the feasibility of directly cutting reinforced concrete pile foundation with Φ 25mm main reinforcement by shield machine, and solve the problems of cutter head stuck, tool damage and low efficiency in cutting pile foundation by shield machine, the pile foundation cutting test with hob and tearing cutter was carried out based on TBM modal tunneling test platform. The results show that:1)the main failure mode of steel bar cutting by hob is rolling failure, and the effective reinforcement breaking ratio is 90.6%. The main failure mode of steel bar cutting by tearing knife is shear failure, and the effective reinforcement breaking ratio is 85.4%.2) Compared with full disc hob, the cutting parameters fluctuate greatly, the cutting process is unstable, and the vibration impact is large. Moreover, due to the large lateral impact force, the tearing cutter alloy has many forms of collapse and collapse. 3) The results show that the impact resistance of the hob is better than that of the tearing cutter, and the forward cutting effect of the tearing cutter is better than that of the hob. 4) It is suggested that the advancing speed of steel bar cutting should not be too fast, and the torque fluctuation should be paid more attention to during the cutting process. It is suggested that the driving speed of tearing cutter cutting pile foundation should not be greater than 3mm / min, and that of hob cutting pile foundation should not be greater than 5mm / min. The test results have been successfully applied to Shenzhen Metro pile cutting project. The test and practice show that it is feasible to directly cut the large diameter reinforced concrete pile foundation with the diameter of 25 mm.

Key words: shield machine；cutting pile foundation, hob, tearing cutter, mechanical characteristics, cutting parameters, fracture morphology