PURPOSE: To improve the ground by a method in which the ends of many underlay nets having many projections are lapped for laying them on the ground, e.g., soft ground, etc., while inserting their projections into the lapped net portions, and a banking is constructed on the nets.

CONSTITUTION: Underlay nets 1 having projections 3 and 3' on its upper and lower sides are connectedly laid on the ground 4, e.g., soft ground, etc., while lapping their ends and also inserting their projections 3 and 3' into the meshes 2. Banking 5 of soil, sand and gravel is then constructed on the nets 1.