OVEREXCAVATING DEVICE FOR SHIELD MACHINE

PROBLEM TO BE SOLVED: To apply a method of 'NOMST' construction to departure and arrival shafts by installing an overexcavating device and forming a passing grove for passing a projected projecting section to the outer circumferential section of a shield frame in a shield machine. SOLUTION: In the shield machine 1, an overexcavating device 40 is mounted to a simultaneous back-filling injection device 25 projected from the outer circumferential section of a shield frame 2 and to the front in the direction of excavation of the projecting section of a putty grease injection device 35. The overexcavating device 40 has a rotary type cutter 45 driven by a hydraulic motor 61, and a cutter 45 is lifted and lowered by a pair of hydraulic cylinders 64 and changed over to the place of overexcavation and the places of a retreat and entrance. Accordingly, the shield machine 1 cuts the 'NOMST' wall of departure and arrival shafts by a cutter disk 3 and a passing opening is formed while a passing groove for passing the simultaneous back-filling injection device 25 and the projecting section of the putty grease injection device 35 is formed by the overexcavating device 40, and the contact and damage of the projecting section and the passing opening are prevented.