CONSTRUCTION METHOD OF SLOPED FACE SURFACE LAYER, RAIN WATER FLOW-DOWN SUPPRESSING METHOD, AND SUPPRESSING METHOD OF RAIN WATER FLOW-OUT TO DOWNSTREAM AREA

To solve a problem that, when a heavy rain occurs and rain water flows down all at once on a long and large sloped face of, for example, about 30 to 60 m, there is a risk that sediment flow-out and a surface failure occur and that rain water more than drainage capacity of a downstream area flows down.SOLUTION: A surface layer structure 10 comprises a first partition member 100 and a first infilling material 122. The first partition member 100 is laid along a surface on a sloped face, and divided into a plurality of regions (cells) 120 (a first region). The first partition member 100 includes an opening. The first infilling material 122 is filled into each of the plurality of regions (cells) 120. By at least one of variously changing an opening ratio of the first partition member 100 and adjusting a particle diameter and particle size of the first infilling material 122 to change a void ratio and water permeability, at least one of a flow speed and a flow rate of rain water flowing down a sloped face surface layer, to suppress flow-out of rain water falling on the sloped face.SELECTED DRAWING: Figure 1 【課題】豪雨が発生し、例えば３０ｍ〜６０ｍ程度の長大のり面を雨水が一気に流下すると、土砂流出や表層崩壊が発生する恐れがあるとともに、下流域の排水能力を超えた雨水が流下する恐れがある。【解決手段】表層構造体１０は、第１区画部材１００及び第１中詰め材１２２を備えている。第１区画部材１００は、のり面に表面に沿って敷設されており、複数の領域（セル）１２０（第１の領域）に区画している。第１区画部材１００は開口を有している。第１中詰め材１２２は、複数の領域（セル）１２０のそれぞれに充填されている。第１区画部材１００の開口率を種々変化させることと、第１中詰め材１２２の粒径・粒度を調整して空げき率や透水性能を変化させること、の少なくとも一方により、のり面表層を流下する雨水の流速及び流量の少なくとも一方を調整してのり面に降った雨水の流出を抑制する。【選択図】図１