PURPOSE: To save natural resources to be used as a back filling material and to reduce several problems accompanying removal of surplus soil.

CONSTITUTION: A groove is formed by digging a road occupying object burial position, a concrete made stabilizer is set on the bottom part of the groove 2, concrete made vertical walls are erected and fixed on both sides of the stabilizer 3, and a protective material 8 is filled in the circumference of and above a road occupying object on both outsides of the road occupying object and inside of the vertical walls of the stabilize 3. A concrete made cover 10 is installed on the upper end part of both of the vertical walls, and back filling restoration is carried out on the outside of both of the vertical walls. A protective device is constituted of the short stabilizer 3, a long stabilizer, the vertical wall 5 and the cover 10.