PURPOSE: To prevent the rolling-up of a drain material by a method in which an extruding rod coupled with a drain material is penetrated, together with a casing, into the ground, and a short time later the casing begins to be pulled up, the rod is pulled up.
CONSTITUTION: A drain material 23 is wound around the tip of the extruding rod 14 of a drain material driver, and a casing 10 is penetrated to a given depth by a vibro-hammer 9. The coupling between the rod 14 and the casing 10 is released and then the casing 10 is raised, whereupon a cover 13 is opened by the rod 14 and the drain material 23 is strongly contacted with the subgrade layer and held there. When a stopper 29 near the upper end of the rod 14 is contacted with and supported on the upper support plate 18, the rod 14 is also pulled up with the casing 10, and the drain material 23 is left behind in soft ground. When the rod 14 is further pulled up, the drain material 23 is rolled up since the surrounding ground is stabilized.
MORI KIYOSHI
UCHIDA YASUSHI
