PURPOSE: To eliminate the drainage of a foamed block structure, by providing the surface of a foamed block used for filling, with a pipe setting groove.

CONSTITUTION: Between the earth pressure working end surface 1 and the wall unit 2 of a sheathing structure for filling inclined as a whole, the foamed blocks 3 of the molded products of foamed polyethylene or the like are heaped up and arranged in the shape of an inverted triangle. In this case, in the longitudinal direction on the surface 21 of the foamed block 3, an object forming a groove 19 for setting a drain pipe is used. When the blocks 3 are arranged, then the drain pipes are arranged on the grooves 19 of the blocks 3, and the blocks 3 on an upper step are turned upside down, and the upper and lower blocks 3 are combined with each other at the mutual grooves 19 to be used. As a result, by inserting pipes into a hill, rain water can be discharged outside the blocks 3.