| 摘要 |
PURPOSE:To cause a nozzle to be protruded in a horizontal direction in response to the pressure of excavating water, by a method wherein a hydraulic cylinder, which actuates a parallel movement mechanism for supporting the nozzle, is communicated with a circuit which feeds the excavating water to the nozzle. CONSTITUTION:A nozzle 1 is attached to the forward end of an excavation pipe 3 through a parallel movement mechanism 2, and a hydraulic cylinder 17 (5), which actuates the parallel movement mechanism 2, is communicated with an excavating water feed circuit 20. In formation of a cavity in earth, with the excavation pipe 3 rotated, ultra-high pressure water is fed through the circuit 20, and excavation is effected through injection of high-pressure water through the nozzle 1. When, with the progress of excavation, an excavating wall surface is moved backward, by increasing the feed pressure of the high-pressure water in the circuit 20 to higher than a given value, a ram 17a is raised against elasticity of a spring 21. This causes the nozzle 1 to be protruded in the direction of the excavating wall surface in a condition to be kept in a horizontal direction to shorten a distance to the wall surface, resulting in the possibility to improve excavation capacity. |
