PURPOSE: To make anchorage of solid reinforcing material feasible by a method wherein a form is arranged on a threshold of an excavated groove, a blind cover is provided to an opening on the outside of the groove, the inside of the form is filled with filling agent, and a protection wall is formed to the surface of a natural ground except the place of the form.

CONSTITUTION: An excavated groove 2 is formed and, at the same time, a belt-like reinforcing material 1 is inserted therein. A form 3 is placed on a threshold of the excavated groove 2, and a blind cover 6 is attached to the form 3. A grout hose 8 is inserted through an insert hole 10 provided to the blind cover 6, and filling agent such as grout is injected through the hose 8. Then a space around the belt-like reinforcing material 1 in the excavated groove 2 is filled therewith, and filling to the inside of the form 3 follows. After the filling is finished, the grout hose 8 is removed from the insert hole 10, and mortar 15 is sprayed to the natural ground surface Ms to construct a protection wall for the natural ground M. On spraying the mortar, the thickness of spraying is determined by using the outer edge of the form 3 as a ruler.