The development of underwater dredging system for rocky sea bottom at narrow channel

Kanmon channel located between Honshu and Kyusyu is a main steamship lane of Japan. On March 1991 the dredging plan to the depth of 14 m was decided. The part of Hayatomo-Strait is restricted by various conditions. At present, dredging to the depth of -13 m, to the distance of 100 m from the side end of the channel, we use a grab dredger which is equipped with spades and anchor lines for mooring. However, we must restrict the navigation at the dredging of the central part of the channel by the present method. Therefore we develop an underwater dredging system. As the sea bed soil consists of weathered rock, we chose a load header for the excavating machine. The paper describes: the excavating machine designed especially for its low height; the electric cable system; the power supply for the excavating machine; the gathering and transporting system; and the control system to operate the excavating machine under invisible underwater condition.