With four kinds of model Front-open-type suction heads which are very hopeful, a series of experiments on dredging pseudo-Hedoro were conducted. As a conclusion, following items can be stated.
(1)It is possible to dredge Hedoro with high solid concentration (55～65% by volume in situ) by using Front-open-type suction heads.
(2)In a case of dredging Hedoro which has low moisture ratio in situ, a suction pattern at suction heads is distinguished into two regions (X-region and Y-region).
　In X-region, all of the Hedoro raked at the model bed is sucked up.
　On the other hand in Y-region, all of the Hedoro raked at the bed is not sucked up due to remaining Hedoro at both sides of the inner wall of a suciton head.
　In the end part of Y-region, dredging performances are unstable and lead to clogging phenomenon of a suction head.
(3)The range in which Y-region can exists is influenced by shapes of suction heads, especially the breadth of them.