To prevent the loss of a reinforcing function of the ground without hindering a movement of small animals in soil after the ground is sufficiently stabilized by constituting woven knitted goods of synthetic fiber physically/ chemically/biologically stable in the soil and unstable fiber, and constituting the opening part having the specific area of stable synthetic fiber.

Woven knitted goods are constituted of synthetic finger A physically/chemically/biologically stable in soil and synthetic fiber B physically/ chemically/biologically unstable in the soil. The opening part area of woven knitted goods constituted of only this synthetic fiber A is set not less than 4 mm. Here, the opening part appears for the first time when only the synthetic fiber B physically/chemically/biologically unstable in the soil disappears so that small animals in the soil such as an earthworm and a lugworm pass/move here. Therefore, a movement of the small animals in the soil is neither hindered after the ground is sufficiently stabilized, nor a reinforcing function of the ground is lost.