In recent activites on port and harbor construction works, many trials on the transportation of dredged soft mud thorough horizontal pipeline by using compressed in injection. However, as far as the designing of such transportation system with compressed air is concerned, it is eager to demand to establish suitable design methods because that present situations are almost based upon the experiences in actual activities.
　With these backgrounds, the room experiments with horizontal pipeline were preformed, in which soft mud with fine particles were flowed by dredge pump and compressed air was injected to the flowing slurry in the pipe. First of all, the fluidity characteristics of soft mud slurry were grasped by the way based on the analysis using power-law model forpseudoplastic non-Newtonian fluid. Then, the fluidity characteristics of soft mud slurry with air mainly including pressure losses for three phase flow were investigated under the consideration of the flow characteristics without air.