PURPOSE:To secure the discharge quantity of earth by providing a pair of closed containers for accommodating sediment, a means for changing the volume of the sediment accommodating space of each container, and the like, and setting the increase quantity of the volume of one sediment accommodating space to be the same as the drilling quantity of a shield machine. CONSTITUTION:A closable discharge opening 30 is provided at one end of a screw conveyor 28 with its other end opened into a cutter chamber, and drilled sediment is received into one of a pair of closed containers 36, 38. The containers 36, 38 are provided with volume changing means 78, and the volumes of the sediment accommodating spaces of the containers 36, 38 are changed by the movement of the pistons 80, 81 of the means 78. The increase quantity of the volume of the sediment accommodating space can be made the same as the drilling quantity of a shield machine by setting the migration speed of the pistons 80, 81 appropriately, and the drilled sediment received into the containers 36, 38 is discharged outside from each sediment discharging opening 72. The quantity of sediment corresponding to the drilling quantity of the shield machine can be thereby discharged positively.
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