PURPOSE: To prevent peripheral ground subsidence caused by pumping and drainage by providing a drainage pump in a drilling construction site, providing a water level detector to detect a water level at the site, and controlling operation of the drainage pump on the basis of the output of the water level detector and the upper and lower limits level of stable water levels.
CONSTITUTION: In drilling construction by a deep well construction method in which a drilling side is divided by a retaining wall A to drill the drilling side, water tends to be collected in a drilling place due to spring water and leaking water by drilling. Hereupon, a plurality of long cylindrical wells are provided which are extended from the ground to a compressed water layer (c) at the lower side of an impermeable layer B, for instance, drainage pumps 2 are provided at the inside of the lower portion of two drainage wells 1a respectively and a water level detector 3 is provided in the other observation well 1b. The drainage pumps 2 are operation-controlled via an inverter 5 by a control unit 4 to which an output signal of the water level is input in a manner that a water level detected becomes controlled water level required within the upper and lower limits of set and recorded water levels.
ONISHI YASUKAZU
SAWAGUCHI MASAHIKO
MARUTA HARUKI
KURIKI SAKIO
