Abstract: The present invention provides a foundation-unit structure of a structural object such as a retaining wall installed fixedly on a foundation ground, in which the foundation ground is formed therein with a concavity, a sliding resistive element is placed within the concavity, and at least the front surface side of the sliding resistive element is filled with a grain-sized material so as to form a layer thereof, and an internal frictional angle of the grain-sized material forming the grain-sized material layer is equal to or greater than that of a grain-sized material comprising the ground and supporting the grain-sized material layer, and the grain-sized material layer exerts a reaction force (passive) via the sliding resistive element so as to reinforce a sliding resistance of the structural object mounted on the grain-sized material layer. In this way, a retaining wall excellent in a sliding preventive function is provided.

Abstract: A plurality of bottom structure members for controlling a tidal oscillation flow are disposed on a bottom in a sea area, thereby creating a new tidal residual current.