PURPOSE: To facilitate the execution of works, in which frost heaving generated on a foundation ground is prevented, by dividing the whole slope underfloor structure into a plurality of pairs of laminated structures, in which a plane shape is formed in a polygon.

CONSTITUTION: The whole slope underfloor structure of an artificial skiing ground utilizing a slope land is divided and formed into a plurality of pairs consisting of the laminated structures A of polygonal planes. Upper structure, in which metal plates are mounted on top faces and which is composed of a heat-insulating material, and lower structure made up of metal plates or precast concrete boards and posts are combined integrally. Consequently, sections transmitting cold heat are decreased, thus effectively inhibiting frost heaving. Accordingly, a slope sectional shape can be formed freely without being subject to the effect of the irregularities of a ground surface while an expansion joint for obviating thermal shrinkage need not be fitted particularly, thus shortening the term of works.