In recent activities on port and harbor construction works, many trials on the transportation of dredged soft mud with high density by using compressed air injection through horizontal pipeline. These trials are the unique slurry transportation method using compressed air in order to decrease apparent pressure gradient, which is quite differ from usual way with large quantity of additional water. Because of an easy separation of air from mud slurry at disposal area.
　However, as far as the designing of such transportation system with compressed air is concerned. It is urgent necessity to establish suitable design method because that present situations are almost based upon the experience in acturl activities.
　Therefore, the authors reported the fluidity characteristics of soft mud slurry with or without air for non-Newtonian fluid, which could bring suitable and qualitative comparisons concerning slurry transportation in horizontal pipe with compressed air.
　In addition, the experimental results in the report mentioned above are studied comparatively with the data of execution by using actual plants, and the methods on suitable designing are also discussed.