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 backhoe and the like are employed and the alien substance 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 alien substances in the mud can hardly be let run through a rotary bar screen 500, the rotary bar screen is turned and thereby the alien substances are scooped up and removed. When relatively hard mud in less fluidity is raked, with water poured thereon, from the inclined bottom face of the hopper and the sloped passage 400 toward the rotary bar screen 500, a backhoe 800 is operated with its paddle wheel 810 provided on the front end thereof driven in rotative motion. After the mud, running through the rotary bar screen 500, is stored in a mud storing tank 600, a screw type pneumatic conveyor 700 is driven, and the mud is conveyed by pneumatic conveyance through a carrier pipe 720 that is laid extending from the barge 100 for pneumatic conveyance to a rock wall or the like.