DISCHARGE METHOD OF DIGGED EARTH AND SAND, AND DISCHARGE DEVICE

PROBLEM TO BE SOLVED: To eliminate the work interruption due to a receiver tank which is full by suctioning digged earth and sand into the receiver tank of a vacuum car and recovering supernatant liquid in the receiver tank into a closed tank at a low position. SOLUTION: A leading pipe 2 advances into a hole formed on a side wall of a starting vertical shaft 1, and a rear end of the leading pipe 2 is pressed to dig the earth and sand by a cutter head at a tip of the leading pipe 2. A soil discharge device is provided with a closed tank 4 which is separate from a vacuum car 3 provided with a receiver tank 5 and a vacuum pump 6 on the ground. The vacuum pump 6 is driven to generate negative pressure in the receiver tank 5 and suction digged earth and sand through a vacuum pipe 7. A basic end part of a water pipe 8 is connected at a lower position than an earth and sand suction port of the receiver tank 5 to separate and recover supernatant liquid in the receiver tank 5 into the closed tank 4. When the closed tank 4 becomes full with water, it is exchanged with the other sealed closed tank so that the soil discharge work can be continued without stopping the vacuum work.