FREE-CROSS-SECTION SHIELD MACHINE

摘要

PURPOSE:To continuously and accurately excavate a tunnel of the desired cross section which is not limited to a circular one. CONSTITUTION:A plurality of cutter arms 70 are rotatably attached to a cutting wheel 2 having a center cutter 6, and a forming cutter 7 which rotates integrally with the cutting wheel 2 to drill earth ahead is provided at the front turning end of each cutter arm 70. The amount of rotational displacement of the cutting wheel 2 is detected and a target amount of operation equivalent to the amount of rotation of the cutter arm 70 required to obtain the track of revolution of each forming cutter corresponding to a preset shape of excavation is computed based on the amount of rotational displacement of a rotor which is detected by a rotational displacement detecting means. The actual amount of rotation is compared with the target amount of operation and the rotational driving of the cutter arms 70 is controlled to make the amounts equal each other.