PURPOSE: To prevent water from invading and penetrating from a boundary point with a bedrock and the interior of a bedrock, by a method wherein a trench is dug in a given bedrock, a material having viscoelastic nature is placed in the trench, and a steel sheet pile is driven in the poured material having viscoelastic nature.

CONSTITUTION: 2 elevated zones 1 are built by placing gravel in a ridge manner on a given bedrock G in a sea bottom to build a trench 2 therebetween. Asphalt mastic 3 having viscoelastic nature is placed in the trench 2, and the trench 2 is full up to the upper sides of the elevated zones 1. A reclamation work is carried out in a way that banking 4 is conducted at an area B containing the elevation zone 1 so as to have a given height from a water surface S, and a steel sheet pile 5 is driven from a banking top part 41 of the banking 4 by means of a drop hammer. This enables shortening of terms of a work, and permits to perform a construction work irrespective of strength of the bedrock.