PURPOSE: To enhance the easiness in execution of works by mounting an earth/ sand raking plate in the form of a plow on the internal surface of a circular casing, scooping earth and sand at the internal surface of the casing in association its swing motions, and raking toward the central part.

CONSTITUTION: A hydraulic cylinder 7 of an earth/sand raking device 3 is contracted to reduce the dia. of a plate 4, and the outside dia. of the device 3 is made smaller than the bore of a casing 1, and the device 3 is sunk to the undermost part of the casing 1 using a rope 10. The cylinder 7 is elongated to enlarge the dia. of the plate 4, and the device 3 is secured to the bore of the casing 1. Then the casing 1 is pressure fitted with swing motions, and the earth and sand at the internal circumferential wall of the casing 1 are with these swings scooped by a cutting edge provided in the upper part of an earth/ sand raking plate 5. The earth and sand are raked to the central part of the casing 1 by this raking plate 5. After exhausting the earth and sand to the outside using a grab bucket 13, etc., and the device is removed upon dia. reduction. Thereby excavation can be executed approx. perfectly with a small-sized grab bucket, and works can be done safely without use of any human labor.