PURPOSE: To facilitate pneumatic conveyance of mud in the case where the mud gathered can hardly be let flow because of its high viscosity or being mixed with alien substances unsuitable for conveyance by a method wherein a built-in rake-up paddle and the like are employed and the alien substances are removed therewith.

CONSTITUTION: Mud gathered with a grab bucket 200 of a barge 100 for pneumatic conveyance of mud is supplied to a hopper 300 and is let flow downward over an inclined bottom face of the hopper and a sloped passage 400. In the case where the mud is such that is hard or highly viscous and can hardly be let flow naturally, a rake-up paddle 800 is operated for facilitation of its movement. Alien substances mixed in the mud are scooped up from the sloped passage 400 by swinging operation of an arm 820. The mud screened out through a fixed bar screen 500 is stored in a mud storing tank 600 and after that, a screw type pneumatic conveyor 700 is driven and the mud is conveyed by pneumatic conveyance through a carrier pipe that is laid extending from the barge 100 for pneumatic conveyance to a rock wall or the like.