To promote the reduction effect of vertical earth pressure acting on the top plate of a culvert and to reduce a material cost for reducing vertical earth pressure.

After the execution of a culvert 10, a group of waste PET bottles 20 for binding a specific number of waste PET bottles 21 with a belt 22 of sheet of construction is spread over the top plate 1 of the culvert, plywood 30 is put thereon, and after a sheet-like filter 40 is covered thereon, banking materials are scattered to roll, and a banking ground with specific height is developed. When overburden load from banking materials reaches specific size in the course of development, since each of the waste PET bottles 21 of a group of waste PET bottles 20 is buckled to suddenly crush it up to the thickness thereof, a ground arch of discontinuity plane projected to the upper side raised from both edges in the direction of the width on the top plate 11 is formed in the ground of the upper side thereof.