PURPOSE: To conduct the separation recovery operation of a drilling casing smoothly and safely by using a cutoff plunger in the drilling casing having a high cutoff function and performing cutoff treatment in the drilling casing.
CONSTITUTION: A cutoff device 15 is passed through the small bore section of the joint section 18 of a drilling casing 5 on the outer circumference of a pressure pipe 17, but the cutoff device 15 is mounted so as to be stopped at the stepped section of the small bore section to water pressure to be applied and cut off water. The cutoff device 15 is inserted into the drilling casing 5, and the drilling casing is drawn out by length, in which the joint section is exposed, under the state, in which the pressure pipe 17 is borne by a holding jig. The exposed joint section is separated, the drilling casing 5 is extracted and recovered, and an injection material is pressed and injected. Accordingly, the re-swelling operation of the holding jig in the extraction process of the drilling casing 5 is facilitated.
MARUOKA MASAO
YAMAMOTO TOSHIAKI
TANIMURA KAZUHIKO
SAKAMAKI TAKESHI
KURATOMI KAZUSHIGE
KOZO KOJI KK