| 摘要 |
PURPOSE:To prevent entrance of underground water into a working chamber, by a method wherein the water pressure at a blade edge is computed from an underground water level and a blade edge position set value, and the water pressure at the blade edge and the atmospheric pressure in a caisson are compared with each other for computation to open and close a regulating valve for regulating the pressure in the working chamber. CONSTITUTION:From the present position of a caisson blade edge 26 set by a blade edge position setter 42 and an underground water level detected by a water level detector 36, the underground water level at the blade edge 26 is detected. The underground water level is converted into a signal by the computer 42 to transfer the result to a comparator 46, and the result is compared with a signal for the atmospheric pressure in a caisson working chamber 14 detected by an atmospheric pressure detector 40. When the signal for the underground water level at the blade edge 26 exceeds the signal for the atmospheric pressure in the working chamber 14, a signal for opening a pressure regulating valve 18 is outputted from the comparator 46. Further, the pressure regulator 18 is opened by means of a signal, and a compressed air is discharged from a compressor 16 to feed the compressed air in the working chamber 14 through a feed air pipe 20. |
