METHOD OF CONTROLLING DIRECTION OF SHIELD MACHINE

PURPOSE:To increase the degree of accuracy of excavation control by measuring the slippage between a virtual turning center and a planning line and the deviation between the center of a segment and the planning line in detail, and correcting the virtual turning center so that the deviation between the real turning center and turning virtual center is reduced to zero. CONSTITUTION:The deviation L1 between a virtual turning center BX and a planning line l1 and the deviation L2 between a locus l2 of the central position of a segment ring and the planning line l1 are measured in detail. After that, in the case the rate of variation of the difference T between the deviations L1 and L2 calculated by a mathematical method is changed rapidly, the distance ab is obtained as the deviation L from the real turning center Q to the virtual turning center BX. Excavation and construction of the segment are made while controlling the direction of the excavation of a shield machine 1 by correcting the virtual turning center BX so that the slippage (off set amount) L is reduced to zero.