Method of creating offshore seabed mound

Abstract

A seabed mound creating method suitable for a construction of a large scale offshore structure comprises the steps of setting up a plurality of sheet piles along the outer periphery of a mound creation region in a seabed area of soft ground to form an earth-retaining wall projecting from the seabed, and raising the ground level of the seabed within the earth-retaining wall by depositing soft soil into the earth-retaining wall to heap the deposited soil to a predetermined height. The method further comprises the step of implementing a ground improvement process to both the heaped-up soft soil and the soft ground of the seabed within the earth-retaining wall so that the ground improvement process is provided to a predetermined depth below the seabed, thus to form a seabed mound integral with the improved ground. The seabed mound may be provided at the upper portion with a projection area serving as a shear key with respect to a horizontal external force. Such a seabed mound can eliminate difficulty in supplying mound materials even when constructing a structure in an offshore area. When the ground improvement process is equally implemented to both a seabed ground and the heaped up soft soil, the seabed integrally formed with the improved ground can be created. Thus, a great shear strength due to such an integral structure can resist a horizontal external force, thereby ensuring high security.