| 摘要 |
PURPOSE:To make it possible to easily form an underground hole with a larger diameter while having advantages capable of easily execution even if a device is compact and even in a narrower space. CONSTITUTION:An underground excavator 3 excavating earth around the existing underground hole 2 to drive forward in the ground while moving a head 19 in and out against a drum section 16 by compressive air and forming a widening diameter underground hole 7 having a larger diameter than the existing underground hole 2, a compressor supplying compressive air to the underground excavator 3 and an absorber to remove-excavated moving-soil through a hose 6 are provided. The underground excavator 3 is so constituted that an excavation widening diameter section 20 to excavate earth around the existing underground hole 2 is formed over the whole circumference on the peripheral surface side of the driving head 19. A cylindrical guide section 21 fitting and connecting one end section of the hose 6 in the direction of the axial center in a relatively movable manner is provided to the front end of the driving head 19. A spring 29 to absorb impulsive force caused by moving the driving head 19 in and out is laid between the cylindrical guide section 21 and the hose 6. |
