It is very important in determining the optimum dumping locations and the limit water depth in dumping works to predict the heap shape of dumped materials in reclamation due to direct dumping with hopper barges in shallow water areas. A series of centrifuge model tests to predict the heap shape was conducted for sand seabed and clay seabed in shallow water. The test results show that the limit water depth in dumping works is about 6 m and the heap shape becomes a trapezoid. It is shown that the stability of clay seabed immediately after dumping can be evaluated by Modified Fellenius Method.
A direct dumping method using bottom open door type hopper barges is one of the alternatives in large scale and rapid reclamation methods. In shallow water, the limit water depth in dumping works and the stability of clay seabed by impact force during dumping needs to be known. Small model tests under Ig in shallow water have been conducted by Mutoh et al. (1974). They focused on only the heap shape on rigid base without considering seabed conditions such as the movement of sand seabed surface and the stability of clay seabed, and showed the sand heap shape to be a triangle. Authors (1999) have indicated that centrifuge model is able to give satisfactory solutions in deep water for same requirements mentioned above. Drum centrifuge model is also used in shallow water. This study shows that the limit water depth in dumping works using a 3000m 3 bottom open type hopper barge is about 6 m and the heap shape becomes a trapezoid like for sand seabed. The clay seabed with the undrained shear strength of 1.2Z (kPa) with depth causes failure during dumping.
