Slipforming method and apparatus for in situ lining of an upwardly open

Abstract

A slipform and method for forming a concrete lining in upright open shafts having been previously filled with a liquid such as drilling mud. The drilling mud below the slipform apparatus is pressurized to push the slipform upwardly within the shaft while it simultaneously forms delivered concrete into a monolithic lining within the shaft. The apparatus includes outer and inner slipform members. The inner slipform member fits within a conical recess of the outer slipform member and includes a lower cylindrical portion for forming the open inside diameter of the lining. Concrete, in a plastic, wet condition, is pumped between the two slipform members to be molded against the shaft wall into an upwardly open monolithic concrete lining. The rate of ascent of the forms is timed in accordance with the setting time of the concrete so that the upwardly moving form leaves a hardened monolithic lining behind. The lining is formed in place in the liquid filled shaft while the liquid (drilling mud) is pumped from above the slipform members to the area below. A hydraulic seal is maintained between the slipform members and the shaft walls. The seal is movable with the slipform members as they move upwardly along the shaft walls. A flotation mechanism is provided in the form of inflatable bladders within the form members to selectively render the form members buoyant.