ELEMENT FOR PROPULSION

摘要

PROBLEM TO BE SOLVED: To propel an element smoothly with high accuracy without affecting traffic facilities on the ground surface. SOLUTION: A main digging device 22 provided with a main cutter 21 is provided at substantially the center of an element main body. A sub-digging device 31 having a pair of digging device parts 33 provided with a cutter 32 having a smaller diameter than that of the main cutter 21 is provided in both side parts of the main digging device 22. The digging device parts 33 are integrally supported by support blocks 34. The main digging device 22 is held between the support blocks 34. The main digging device 22 can be attached and detached in the axial direction between the support blocks 34.