To surely protect a structure by providing a surrounding wall disposed in a streamline shape along a side flowing direction so as to surround the structure in the ground of the outer periphery of the structure.

In the ground of the outer periphery of the footing 9 of a bridge pier erected along the sea, a surrounding wall 10 is buried in a streamline shape along a side flowing direction A in the ground of an outer periphery by combining a plurality of steel plates so as to surround the footing 9. The surrounding wall 10 is buried so as to go over a stratum which possibly causes side flowing and reach a lower layer having no possibility of side flowing. An improved non-liquid ground base 20 is provided inside the surrounding wall 10, and the ground 20 is composed of cement milk pillars 21 disposed along the surrounding walls 10 and another improved ground part 22 compacted by deep pipe blowing in a further inside part and made independent from the ground having side flowing possibility in the outer periphery of the surrounding wall 10. Thus, a structure is surely protected from side flowing following the liquefaction of the ground.