PURPOSE: To form a gap in a bottom of an outlet work body and to enable to perform a reliable implantation of grout, by a method wherein a wire net is placed halfway between a bottom of an outlet work body and a lower end of a web, and in parallel to the bottom of the outlet work body, and baseboards are situated to the opposite ends of the web.

CONSTITUTION: A wire net 7 is located halfway between a bottom 2 of an outlet work body 1 and a lower end 5 of a web 4 and in parallel to the bottom 2 of the outlet work body 1, and baseboards 8 and 8' are attached to opposite ends 6 and 6', respectively, of the web 4. The outlet work is installed on a driving surface X-X of lift concrete A by means of a support 13. Lift concrete B is then placed. A gap 11 between the bottom 2 of the outlet work body 1 and the lift concrete B firstly placed is filled with grout C implanted through gaps 12 and 12' between both side boards 3 and 3' and baseboards 8 and 8' of the outlet work body 1. Life concrete is then deposited, in order, to bury the outlet work.