Apparatus for dewatering boreholes

Abstract

A simple dewatering system comprises hollow expandable bore-plugging body which can be set in place and locked there in the borehole, at any desired level, by simply pumping compressed air into it. An orifice of calculated size in the bottom of the body allows compressed air to escape and build up pressure below to raise the water in the lower part of the hole to the ground surface through a conduit which extends from the borehole bottom to a level above the ground. The orifice, which may be adjustable, maintains a predetermined minimum pressure differential inside the body which pressure is enough higher than the water-expelling pressure below to keep the body tightly inflated so it cannot slide upwardly. Compressed air escapes continuously through the orifice so that outflow of water from the borehole bottom is continuous until the water level reaches the bottom of the outflow conduit, when the conduit is blown clear, preventing run-back of the water in the conduit. The body and the outflow conduit may be enclosed in a sleeve or liner of impervious flexible sheet material which lines the inner borehole surface and prevents loss of compressed air through fissures or other pores or openings in the rock formation where the hole is located. To withstand high pressures, a protective shroud of metal mesh is used to limit stretching of the expandable body.