CHANGING OF EXISTING CULVERT AND EXCAVATOR USED THEREFOR

PURPOSE:To realize a muddy water pressure type shield method by pressurizing muddy water in a facing closed section, excavating along bends of an existing culvert while securing the stability of a bedrock and, at the same time, discharging scraps together with muddy water. CONSTITUTION:A cylindrical guide pipe 5 and a rubber bag shaped elastic seal member 10 are provided to an excavator 4 equipped with a cutter head 6 and a driving jack 9, and a closed section 11 enclosing an excavated facing section of an existing culvert 3 is formed. After that, reaction force is applied to the culvert 3 to provide an excavation direction controller 8 setting all directions. Then, a feed pipe 14 sending pressurized muddy water to closed section 11 and a delivery pipe 15 discharging pressurized muddy water from the closed section 11 are provided. Then, the pressurized muddy water is delivered to excavate while preventing the fall of ground 2 and, at the same time, excavated scraps are discharged together with muddy water. According to the constitution, a facing can be held with stability and, at the same time, constitution can be carried out efficiently.