PURPOSE: To increase the strength against a earth-and-water pressure and raise a water stop property by arranging an iron-rod assembled body of space truss form and thus forming a continuous wall united with the set substance of a stabilizing liquid.

CONSTITUTION: A groove hole 10 is made in the ground, while the collapse of the wall of the hole being prevented through the filling thereof with a stabilizing liquid such as bentonite grout. Next, an iron-rod assembled body 12 of space truss form is inserted at certain intervals in the groove hole 10. The iron-rod assembled body 12 is an assembled body of space truss form prepared by joining many plane trusses into one body of required dimensions. The stabilizing liquid is set inside the hole, not being removed out of the hole 10. The set substance 26 of the stabilizing liquid thus formed is a consolidated substance which has non-waterpermeable property and can be excavated, and constitutes a continuous underground wall united with the iron-rod assembled body 12 within the groove hole 10. After that, the timbering consisting of waling 30 and strutting 32 being provided on one side of the underground wall 28, the pit excavation is performed, thereby a landslide protecting wall 34 is constructed.