| 摘要 |
PURPOSE:To excavate a tunnel having an elliptical cross section. CONSTITUTION:Circular cutter plates 3, 3 are disposed on both side portions of the open end of a skin plate 1 having an elliptical cross section and circular tunnels are excavated in parallel to each other along both side semicircular curved plate portions of the skin plate 1 by the cutter plates 3, 3. End portion cutters 7 are disposed along the respective inner surfaces of the upper and lower rectilinear portions of the skin plate 1 and that part of the ground which cannot be excavated by both side circular cutter plates 3, 3 is excavated by the upper and lower end portion cutters 7. |
