To provide a chip discharging method for sufficiently discharging chips produced in boring an existing pipe under the conditions of constant water, from the inside of a sealed case to the outside without causing the chips to reside on the lower side of a sluice valve.
In this constant water boring technique, a chip reservoir 28 into which the chips produced in boring work drop is provided in a space S inside the sealed case 2. The chip reservoir 28 is located on the lower side of the existing pipe 1 at a central portion of the existing pipe 1 in its pipe axial direction L, and a discharge port 25 is provided in the sealed case 2 at a position corresponding to the chip reservoir 28 in the sealed case 2 or behind the chip reservoir 28. The technique comprises a discharge step of discharging the chips from the discharge port 25 together with water which flows out of the existing pipe 1 in boring work and then flows from the space of the chip reservoir 28 toward the discharge port 25.
ITO YASUHIKO
SHIMIZU TOSHIHIKO
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