PURPOSE: To reduce the manual work and provide safety by mechanizing the caisson type pile construction.

CONSTITUTION: A tubular guide shaft 2 is suspended from a pit mouth frame 10 with shaft hoisting devices 12 and cables 13. Each guide shaft 2 is fixed by shaft grippers 7, 11. A main work machine 20, auxiliary work machines 25, 36, and a man/load-conveying gondola 35 are suspended from external cranes 15, 30 with rope trolleys 17, 32 and cables 18, 33. An optional underground machine, e.g. the main work machine 20, is inserted into the guide shaft 2, and it is lowered to the excavation work area 79. The main work machine 20 is fixed to the guide shaft 2 with a gripper 22 to excavate the ground 80. Various underground machines can be quickly replaced in response to the soil property, and each underground machine can be fixed for a strong excavation.