PURPOSE: To qucikly open a suction nozzle even when the inlet of the nozzle is blocked with sandy sludge by a method in which a longitudinal wate suction portin is provided near the sandy sludge suction port of the suction nozzle and a water conveyance portion with a partially lapped portion on the water suction portion and the inlet portion is provided.

CONSTITUTION: A slender water suction hole 11 of a width of (b) and a length of (l) is provided near the inlet 10 at the tip of a suction nozzle 6, and an U-shaped piece 12 is attached to the upper end of the water suction hole 11 in such a way as to form a lapped portion (c) of a length of (l') between the hole 11 and the piece 12 in order to form a water conveyance path 13. When the nozzle 6 is buried in large amounts of sandy sludge 3, since the inlet 10 is closed, the suction of water is made with high speeds from the water conveyance path 13 having a smaller cross section than the inlet. As a result, sandy sludge (a) nearer to the lapped portion (c) is sucked up with flowing water and the sludges (b), (c),...(g) are sucked up over the quickly expanded range, whereby eliminating the blocking of the inlet 10 with sandy sludge in a short time.