Abstract: In order to improve construction efficiency, it is necessary to study the feasibility of directly cutting largediameter pile foundation by shield and the performance of hob and cutter and to obtain the key driving parameters of shield. A model experiment of directly cutting largediameter pile foundation by shield is carried out. The results show that: (1) Grinding method, "low propelling speed and high rotational speed", should be adopted for shield to cut pile foundation of largediameter, and the propelling speed of cutter head is suggested to be 3~5 mm/min, the rotational speed to be 1.0~1.2 r/min. (2) The hob is more favorable to concrete, while the cutter is more favorable to steel bars. (3) The higher the concrete strength, the better cutting effect of hob on the steel bar. (4) The axial vibration of cutter head is obvious when the hob cutting piles, but it is less obvious than that when the cutter cutting pile foundations at low propulsion speed and rotation speed. (5) The hoop vibrationg of cutter head is strong as cutting pile foundations, and it is easy to be jamed under high propelling speed, while increasing rotational speed can effectively reduce the stuck times of cutterhead.

Key words: shield, large diameter pile foundation, shield cutting pile experiment, removal of pile foundation, hob, cutter