PURPOSE: To make effect of groundwater to a banking structure avoidable even if the water level fluctuates by stacking up plastic honeycombs in a part of banking where the water level fluctuates so that the axial direction of the honeycombs are arranged properly in vertical position, and by further stacking up blocks made of EPS over there.

CONSTITUTION: In a part B of a banking where the water level fluctuates, a unit of or a plurality of units of plastic honeycombs 6 made of polypropylene or the like are stuck up with their axial direction arranged properly in vertical position and blocks 4 made of EPS are further stuck up over there. The honeycomb 6 is usually made of bundled hexagonal straws, and the height (1) and sectional area (S) of the straw can be made optionally different according to place and purpose of the banking. In the case of fluctuation in the level of the groundwater in the baking 2, the water moves freely upward and downward inside the straws of the honeycombs 6, preventing the structure of the banking 2 from collapsing by floatage. Thereby effect of fluctuation in the level of the ground-water in the banking can be easily avoided.