| 摘要 |
PROBLEM TO BE SOLVED: To prevent the leakage of slurry in a spring-water sand layer, etc., by installing an on-off valve to an air suction channel disposed to a soil-sand discharge channel and interrupting the air suction channel at the time of excavation stoppage. SOLUTION: When vacuum suction force from a vacuum suction apparatus on a ground works into a coil-sand discharge piping 16 through an earth-removing pipe 20, an on-off valve 19 consisting of a check valve mounted on a piping 17 for air suction is opened and air is flowed into the pipe 16 through the piping 17, and a high-speed air flow towards the vacuum suction apparatus through the pipe 20 is generated in the pipe 16. Excavated materials are rolled into the high-speed air flow when they are flowed down from a screw conveyor 10 to the pipe 16, they are removed into a tank for the vacuum suction apparatus. When a buried pipe 15 and the pipe 20 are extended in a starting shaft, the valve 19 is closed automatically because the connection of the pipe 16 and the vacuum suction apparatus is interrupted and pressure in the pipe 16 is increased up to atmospheric pressure. Accordingly, even when the ground consists of a spring-water sand layer, etc., leakage into a header pipe and the buried pipe through the pipe for air suction of slurry in excavated materials can be prevented. |
