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.
　However, as far as the designing of such transportation system with compressed air is concersed, it is urgent necessity to establish suitable design method because that present situations are almost based upon the experience in actural activities.
　In this paper, the experimental results in the former report are studie comparatively with the data of execution by using actual plants, and the methods on suitable designing are also discussed. For the mud slurry with high density in two places, many items on pressure gradient, pressure fluctuations, separation pattern
of air and mud slurry in pipe, theoretical efficiency for this transport system, etc. are clarified through this worlds.