| 摘要 |
PROBLEM TO BE SOLVED: To improve stability of a banking structure by making a foaming plastic block used for at least one layer containing a hollow lowest bottom part, that of higher density than a foaming plastic block used for an upper part thereof. SOLUTION: According to sharpness of inclination of a rear surface inclination place 2, a banking structure has a high and large scale in the case of the same widened width, and a sliding force is liable to occur more downward in the inclination direction of the rear surface. In this case, the sliding force acts as a compression force on a foaming plastic block 1 and a large compression stress acts dovmward so that a lowest layer in section of the block 1 receives a largest compression force. A high density foaming plastic block 1b is therefore used in one layer containing a hollow lowest bottom part between a front surface wall 3 and the rear surface inclination place 2 so as to cope with the copression caused by the sliding. It is prefarable that the density of the block 1b is not less than 22 kg/m and a polystylene foaming body exellent in strength and water resistance is used therefor. Accordingly, generation of large plastical deformation can be prevented.
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