To continuously construct a main line tunnel and a widened tunnel, shorten a construction period of a tunnel construction and provide an inexpensive excavating device.
When the main line tunnel 5 is constructed, earth and sand excavated by a cutter head 33 of a second excavating device 30 are returned and buried to a space formed between the outer peripheral surface of the main line tunnel 5 and the inner peripheral surface of a hole 3b excavated by cutter heads 16 and 33 by a screw conveyor 40 disposed between respective skin plates 17 and 35 of a first excavating device 10 and the second excavating device 30. When the widened tunnel is constructed, a rear part of the skin plate 17 of the first excavating device 10 and the screw conveyor 40 are removed, a shield jack 27 is disposed along the skin plate 35 of the second excavating device 30 to excavate and segments for the widened tunnel are assembled along the skin plate 35 to construct the widened tunnel.
TAKAHASHI YOSHIYUKI
IZUMI KUNIHIKO
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