WATER RETAINING MEMBER FOR LAND IMPROVEMENT AND LAND IMPROVEMENT METHOD

摘要

PURPOSE:To keep the shape of a water retaining layer over a long period of time and to develop certain water retention by providing water permeable sheets different in water permeability on both surfaces of a flat plate-shaped water passing member having a large number of water passing holes formed thereon in the thickness direction thereof. CONSTITUTION:A water retaining member 1 is formed from a water passing member 12 and the first and second water permeable sheets 11, 13 provided on the upper and lower surfaces thereof. The respective water passing holes 14 of a plastic structure 12 are formed as a hexagonal honeycomb structure and have upper and lower opening parts. The first water permeable sheet 11, the flat plate-shaped water passing member 12 having a large number of water passing holes 14 formed thereon in the thickness direction thereof and the second water permeable sheet 13 are stacked in this order from the earth's surface and the water permeability of the first water permeable sheet 11 is made higher than that of the second water permeable sheet 13. The plastic structure 12 and the water permeable sheets 11, 13 are bonded by a welding means and the penetration of gravel into the water passing holes 14 due to soil pressure is prevented.